This article by Jerry Cates (initiating author) and Adette Quintana (editor and contributing biologist), first published on 14 November 2018, was last revised on 22 November 2020. © Bugsinthenews Vol. 20:10(03).:
A Brief Review of Rat and Mouse Control
Ralph Waldo Emerson (b. 25 May 1803 – d. 27 April 1882) once wrote that “If a man has good corn or wood, or pigs, to sell, or can make better chairs or knives, crucibles or church organs, than anybody else, you will find a broad hard-beaten road to his house, though it be in the woods.”
Seven years after Emerson’s death, the wordy preamble of that original passage was published in reduced form, referring simply to writing a better book, preaching a better sermon, or making a better mousetrap. Later it was shortened even more, until today, we most often find the context limited to simply building a better mousetrap, which induces those in need of such contraptions to beat a path to your door.
Though Emerson never actually penned the now-oft-repeated “Build a better mousetrap, and the world will beat a path to your door,” he championed its truth. That put him in good company.
Humanity has recognized rats and mice as pernicious scourges for millennia. The “science” of rodent control has occupied human minds for at least as long. Early on, perhaps, control methodology was no more complicated than whacking every rat that could be found with a rock or a club, so science yielded to brute force most of the time. Even in ancient times, however, technology advanced steadily forward, ostensibly to produce methodologies that were safer and more effective.
Besides “whacking” and all the kindred mechanical devices of like kind (including precursors to today’s still-going-strong snap-trap) perhaps the most ancient hi-tech way to control rats and mice involved domesticating cats for that role. According to Andrew Kitchener, PhD zoologist at the National Museums of Scotland, domesticated cats first surfaced in Mesopotamia, more than 100,000 years ago. So loved were these mouser felines that, by 450 BCE in Egypt, the penalty for killing a cat was death.
Cats are Good Mousers, but Poor Ratters…
While cats have a long and storied history in the rodent control business, and are quite good at killing mice, they are notoriously inefficient at killing adult rats. On the contrary, adult rats tend to make most cats cower. Numerous published YouTube videos record how rats successfully attack cats and get away with it.
In a 2017 5-month study at a Brooklyn recycling plant infested with over 150 wild rats, 5-7 feral cats were also found to inhabit the same plant grounds. Over the 5 months of the study, motion-triggered cameras planted by the study’s crew recorded only two instances of cats killing rats, and the number of rats there appeared to be as high at the end of the study as when it commenced.
The authors witnessed a similar condition at a large restaurant in north Texas that — through no fault of its own — had become infested with large numbers of rats. Despite hosting, in the building’s spacious crawl space, more than 15 feral cats, the rat population continued to grow. The cats were not alone in their failings. The highly respected pest management firm that restaurant contracted with to handle all their pest issues was just as unsuccessful, though its technicians seemingly used every control method at their disposal.
Brought in by the restaurant as consultants, we soon discovered that no effort had been made to get the restaurant’s staff to change the way food waste was being handled. Only after this and a number of other important changes were made, could control be achieved. Today the restaurant is rat-free. The feral cats, for their part, remain in large numbers. To the casual observer (including some of the restaurant’s staff), those cats are doing a yeoman’s job of keeping the rats under control, but that is far from the truth…
It is natural to assume a gang of feral cats hanging around a restaurant’s exterior are there to keep rats away. Yet, if that is true, would we expect to find — as we so often do — an abundance of both rats and cats in most of today’s American residential neighborhoods?
This seeming paradox simply points out that cats are not and can never be the ultimate answer to any locale’s need for rat control. As a rule cats cannot provide even rudimentary rat control in most venues. For the cats involved that’s a blessing. Rats fight their predators with a vengeance. Cats risk serious bite injuries in the process, but the risks posed by rats to our feline friends transcend mere mechanical injury from their incisors. They and their parasites carry life-threatening infectious diseases no cat needs exposed to. Their parasites also infest the cats that are foolish enough to touch and — worse — eat them.
Raptors Aren’t Particularly Good Ratters, Either…
The paragraph heading, above, may give the impression we don’t think raptors are very good at killing rats. That’s not the case. As the authors point out in another article, raptors — birds of prey like owls, hawks, eagles, harriers, etc. — are much better than cats at killing rats. No rat can defend against the raptor’s speed, its sharp beak, and its muscular, bone-breaking talons. Still, even they are not the answer to rodent control.
Most cats are afraid of attacking adult rats, but few raptors fear their rodent prey. Still, as with cats, both raptors and rats abound in most of today’s American residential neighborhoods. Raptors love eating rodents, but they aren’t very good at keeping the rodent populations down in the areas they patrol. Why this is so is complicated. Like many of life’s conundrums, the devil is in the details.
Being the best doesn’t always translate into regular, stellar performances. Competing priorities intrude. Though raptors are definitely the best of all our wild animals at killing rats, they — like us — observe a kind of informal culinary pyramid. For most raptors, rodents are not the only — or even the most tempting — of all their dietary options. Given the range of food choices within typical urban, suburban, rural and wilderness ecosystems, rodents are almost never at the very top of the raptor’s list. Songbirds, amphibians, and large insects often are eaten much more often than rats and mice.
Don’t tell that to the people who run the RATS project (whose name, RATS, is acronymic for “Raptors Are The Solution.”), though. The good folks at that organization promote what is, in the main, a good cause. We take no joy, therefore, in casting doubt on the basic premise behind their raison d’être.
To hear them tell it, though, raptors exist for one thing only, to kill every rat they can find. If that was true, we might be inclined to believe raptors capable of keeping rat populations down to acceptable levels. Our research shows, however, that the assertion that “Raptors Are The Solution” to rodent control is simply not true.
“But,” you ask, “why not?” That’s a good question, and it deserves a good answer. That answer comes in several parts, the last of which may surprise you.
First and foremost, raptors reproduce slowly, while rats reproduce so rapidly that it is impossible for raptors to keep up. Please understand what this means. No matter how many are found in a particular locale, so long as raptors provide that locale’s only rodent control measure, the rat population will always be high. This results strictly because of the prolific way rats multiply.
For humans, that’s a curse, but for raptors and other rodent predators, it’s actually a blessing. It guarantees them a steady — though somewhat boring — food supply. Even if they grabbed every rodent they could find (which they don’t), they’d never make much of a dent in their numbers. This dreadful picture isn’t limited to raptors and rats, by the way. In typical ecosystems a kind of uneasy but predictable stasis between prey and predators (most wild animals prey on rodents) is established and maintained, usually as a natural consequence of the way the prey/predator relationship evolved.
This rule does not apply wherever prey or predators are introduced, alone, to ecosystems devoid of their counterpart organisms in the prey/predator dichotomy. Introduced prey absent an effective predator counterpart quickly overpopulates that ecosystem, while predators without prey soon migrate elsewhere or starve. But for organisms that coevolve, worldwide, over lengthy periods of time — as did rodents and raptors — the predicted prey/predator stasis almost always prevails.
For humans who think they can rely solely on raptors for rodent control, the rat/raptor stasis typical of human-occupied ecosystems has far-reaching, negative implications. lt is not a stretch to assert that commensal rat infestations likely pose the greatest epidemiological risk to human health of all the pest issues that afflict mankind (we discuss this topic in greater detail later.) We feel comfortable making that assertion based simply on the fact that so many different diseases are known to be carried and transmitted by these animals, but there is more to the story than that fact alone.
The U.S. Environmental Protection Agency (EPA) began publishing a list of pests afflicting humans in 2002, and has made regular additions and deletions to that list since. The latest version of that list was published in draft form on 4 November 2020 for public review and comment. It contains almost too many organisms to count, but a careful review reveals a very interesting point: many of the line items on that list — possibly even the majority — are either directly or indirectly associated with rats and mice. In other words, just having mice and rats around your home or business probably exposes you to more dangerous organisms on that list than any other factor.
Ranking the members of the EPA list of pests of significant public health importance would be difficult, as so many parameters cloud the picture. When taking into account all those parameters that are associated with rats and mice, though, one thing is clear. Allowing rodents to nest, loiter and multiply in places where humans live, work, and play should never, ever, be an option.
There is another part to the question of why raptors cannot be the answer to rodent control that we have not yet discussed. Rats — being mostly nocturnal — are adept at hiding their presence to the point that raptors have a hard time finding them.
Owls as Rodent Predators…
Even owls, those raptors that prowl our neighborhoods throughout the nighttime hours, cannot keep rats in check. Here, the explanation why is not only surprising but somewhat ghastly. Most raptors that prey on rats and mice prey just as heavily on other birds — including raptors — as on rodents.
A good example are great horned owls, which make up a significant proportion of many a neighborhood’s owl population. These large birds of prey often spend more time preying on other raptors — particularly screech owls — than on going after rats and mice. You may want to keep that in mind if you are ever tempted to put up owl nesting boxes in your yard. Those who make the mistake of having boxes for both great horned and screech owls near one another learn the hard way that once a great horned owl starts nesting there, their screech owls become history in short order.
Owls are not the only raptors that regularly enjoy eating their own kind, often in preference to rodents. Practically every raptor species practices the same predilection for killing and eating other birds, including those we consider raptors, as an important if not major part of their food intake. The only exception we know of are ospreys (Pandion haliaetus), which subsist almost entirely on live fish caught near the surface of the waterways they patrol, and almost never prey on other birds. Ospreys almost never prey on rodents, either, we hasten to add…
The lesson, to those who study raptor and rodent biologies together, is clear. Though definitely part of the solution, raptors alone cannot prevent rats from proliferating wherever abundant food and habitat is available.
The authors would be remiss if we did not congratulate the RATS Project for the good they have done and are doing. A major thrust of the program RATS promotes is to expose the injudicious use of dangerous rodenticides, and that work has produced generally good results.
Banning All Rodenticides?
We say “generally” because the RATS Project seeks to ban the use of all rodenticides, entirely. That is a goal which we believe to be logically and intellectually untenable, and we illustrate why we believe this by way of an analogy involving the application of many of the medicines used to combat mankind’s most dreaded diseases:
Most lifesaving medicines are, in the wrong dosages, toxic enough to kill. Yet, when used correctly, they work miracles. Like them, rodenticides are important tools in the right hands, though they do need to be administered carefully by responsible, licensed professionals.
Intelligent, Responsible, Science-driven Rodenticide Applications…
When administered by those with the necessary expertise and experience, applications of carefully chosen rodenticides — safely distributed in specially designed, tamper-resistant enclosures — accomplish feats no other rodent control method can. They enable the complete extermination of all the rodents currently inhabiting and reproducing within a given locale.
When coupled with an intelligently designed, science-driven program of rodent control, the judicious use of clean, uncontaminated and palatable rodenticides can keep large areas totally free of rodent nesting and maternity activity for as long as the program is kept in place and properly maintained. They do this by eradicating interloping rodents, migrating from surrounding areas, quickly and effectively, before nest-making and maternity activities commence within the serviced area. Raptors, by their very nature, are absolutely incapable of either of those feats.
An Important Note: While finding fault with the basic raison d’etre that drives the RATS program, we enthusiastically support their efforts illuminate poor, irresponsible and unprofessional rodent control practices, and their push to foster practices that not only follow the law, but that design and execute rodent control programs in ways that limit or eliminate risks to non-target-organisms, not only to raptors but to others as well.
The Impact of Rodent Control Failings on Human Language…
The failure of felines and raptors to control rodents has impacted human language the world over. If cats and/or raptors were successful at rat and mouse control no human language would ever have needed to include the word “mousetrap” in its lexicon. Indeed, contraptions intended to trap and/or kill rats would also never have been needed if cats and raptors lived up to what many humans think to be their highest callings.
Yet, mousetraps, rattraps, and rodenticide dispensers of all kinds enjoy a brisk market today. This is clear evidence that the wisdom attributed to Emerson has caught hold of many an inventive mind. Again, however, the fact that so many kinds can be found — while rat populations continue to proliferate — proves not one of those inventors has thus far designed a truly effective rat control device.
So, not only have raptors and cats failed us, so have ALL — yes, without exception — ALL the man-made rodent-control devices now on the market. This paper, throughout, examines and explains why this is so. Forgive us for the ponderous way we have presented this evidence, but we know of no other way to properly present it.
This paper also explains how the EntomoBiotics E2M2C™ program — developed in the EntomoBiotics Inc. Laboratory to provide an alternative to reliance on man-made contraptions and rodenticides alone — works so well to help close the gap between rodent control failures and successes.
One element so important to the E2M2C™ program is that it refuses to rely solely on off-the-shelf rat-control devices and products. Instead, it makes major safety and efficacy modifications to all those devices it incorporates in the E2M2C™ program before they can be used. Then — perhaps as the most important element of all — it employs a comprehensive methodology that, for one thing, insists on the active cooperation of the occupants of the control site to ensure the program works at peak efficiency.
Rodent Exclusion & Trapping, Crown Jewels of Rodent Control?
Now that we have been discussing rodenticides and the dangers associated with them, perhaps it is time we went over the alternatives to rodenticide use. The value of controlling rodents whenever possible without having to use rodenticides is real and compelling.
Rodent & Wild Animal Exclusion…
There is no question but that, when it is safe and economically feasible to do so, all structures that humans live, work, or play in should be constructed and maintained in a way that prevents surreptitious entry by rodents and other wild animals. That’s something we should all agree on. While the basic concept involved makes excellent sense and is easy to articulate, putting it in practice is much more complicated.
The wildlife camera image posted at the head of this section helps explain some of those complications. Here a young lady living in Austin, Texas, spent $thousands to have her modest, single-family home sealed agains rats and mice. Not long afterward, she began hearing noises in her attic again, and those noises sounded exactly like the noises that had caused her to drain her bank account. This sequence of events is not atypical. In fact, it happens more often than not, for one very good reason.
Most companies that specialize in sealing homes against rats and mice focus on the sealing process, and neglect general rodent control procedures, either by giving it only limited attention or by ignoring it altogether. They do this for at least two reasons. Rodent exclusion is, by itself, a very costly operation. Serious, effective general rodent control generally adds a significant layer of expense on top of that.
Pest management is a highly competitive industry. It is common for business and home owners to get several quotations before selecting the company to solve their pest issues, and the competing companies do their best to keep their total quotations as low as possible. Tacking on more money to kill the rodents in the grounds risks losing the sale, particularly if the customer does not see why the added costs make sense. It is an interesting testament to the present state of rodent biology — both in academia and within the pest management industry — that so few pest management professionals are willing or able to explain those values to the people who most need to know.
OK, so what’s the big deal? Read on…
The Importance of General Rodent Control, Both in Structures and in the Surrounding Yards and Grounds…
How important is general rodent control? We assert, with confidence, that it is very important… Much more important, in fact, than most people think.
Many readers will think the authors are exaggerating. In actual fact, it would be difficult if not impossible to do that. What follows explains in some detail why good, consistent, effective rodent control matters in crucial ways. The details provided here are not mere expressions of opinion, but consist of hard, well-researched and verified facts gleaned from scientific literature spanning several hundred years of research. Much of that research has been conducted in only the past century, but some comes from ancient writings by scientists from long, long ago.
Please learn this truth, and take it to heart: Your health and that of your loved ones depends on keeping rodents at bay, not only in your home, but in your yard and grounds as well. If everyone realized just how dangerous it is to have these furry critters nearby, our ho-hum attitudes toward them would change dramatically.
Not only is general rodent control generally given lackadaisical treatment by the public, even many pest management professionals treat the subject with a kind of disdain. How else can we explain the proliferation of rodent exclusion companies whose focus starts and ends with sealing homes to keep rodents out?
It is not hard to understand why expensive rodent exclusion projects are undertaken without simultaneously eliminating the rats nesting and foraging in the yard. When the exclusion project is so expensive the home or business owner cannot afford to add anything more to the bill, the most basic rodent control measure of all — exterminating the rats in the home’s immediate environment — must be neglected entirely. In reality, excluding rats from a home’s attic without doing anything else simply cedes the yard to the rats. NewsFlash: They don’t go away just because they’ve been evicted from the home.
Indeed, the temporarily excluded rats keep looking for a way back in. All too often they manage to defeat the exclusionary work for which the homeowner paid dearly, sometimes in weeks or months, other times only after a year or two. But even if that doesn’t happen quickly, allowing them to continue living in the yard with impunity results in deposits of fresh fecal pellets and urine all over the front and back porches and throughout the landscape. Our research shows commensal rodent activity is concentrated at the front and back porches at most of the sites we service. Remember, “commensal” means “eating at the same table.” These rodents owe their lives and existence to humans; the closer they can get to where humans congregate, the happier and healthier they are.
The young lady mentioned with the above photo fell victim to that process. She heard scratching in the ceiling, called a company skilled in excluding rats, and paid them to have her home sealed tight to keep them out. She didn’t think to ask what happens to the rats in her yard, and the contractor did nothing to address them. When, several months later, those rats figured out how to get around the extensive and expensive seals the contractor applied, the scratching in the ceiling resumed.
She had never been told eliminating the rats in the yard is as important as keeping them out of the house, and that’s on them. But, to be fair, sometimes the exclusion contractor is not to blame, but is severely limited by the homeowner with regard to what can and cannot be done. Some readers may find this difficult to believe, but many people simply don’t want the rats and mice in their yard harmed in any way.
Rodentiaphilia is Alive and Well throughout America…
Rodentiaphilia (the love of rodents, rats included) is fairly common today. The authors know this first hand, because they are often called to homes infested with rats and asked to conduct a control program that leaves the rodents unscathed. Some just want the rats captured in live traps and relocated to wilderness areas, while others intentionally limit the control — specifically out of respect for the safety of the rodents — to sealing their homes and businesses to keep rats and mice out, while happily leaving them otherwise free to roam anywhere they like, outside.
That’s not what the lady mentioned above did, mind you. She simply relied on the company that sealed her home to do the right thing. To them, “the right thing” meant simply sealing the rats out of her house without worrying about eliminating them from the yard. That’s different from cases where a homeowner insists on having “rat control” carried out that way.
When the authors meet with such homeowners, we respond by asking questions. In some cases the answers tell us the homeowner has concerns that have nothing to do with a love for rodents, but much of the time it does. It bears examining why rodentiaphilia afflicts so many. The reasons why, though, are not hard to uncover. The entertainment industry has played a crucial role in encouraging that mindset.
The Influence of Willard, Ben, Micky, Minnie, and Mighty Mouse…
Rodentiaphilia appears to be fostered by at least two separate and distinct mindsets. One of these is illustrated in two horror movies, namely “Willard” (1971), and its sequel “Ben” (1972). Both promoted the dark side of rodentiaphilia, with lasting effect. “Willard,” based on the short novel “Ratman’s Notebook” by Stephen Gilbert (published in 1968), features an unnamed misfit who relates better to rats than to his fellow humans. The psychology illustrated in that novel and the two movies it spawned has probably held sway over a fair fraction of the human psyche for as long as humans have been sentient.
For example, rebels who rail against established authority, and who feel disenfranchised, marginalized, or alienated from society, are likely to see an important part of themselves in the human protagonists the films portray. As a result, the rodent heroes that befriend those protagonists become models for the wild rats and mice they encounter in real life. If they perceive that human society as a whole despises rats and mice, that’s all the more reason to love and protect those furry creatures.
Of the rodentiaphiles the author meets in his work these days, only a few appear to espouse the mindset described above. The majority, instead, appear to take their cues from portrayals of rodents in roles that have them acting in ways that shore up the existing order, and that benefit mainstream society.
Anthropomorphic portrayals of animals with human feelings, goals, and other attributes first emerged in the 19th century, beginning with Lewis Carroll’s Alice in Wonderland and Rudyard Kipling’s The Jungle Book. In both of these cases the animal characters portrayed appealed to the deepest senses of the human spirit. Carroll actually sought to explain complex mathematical and metaphysical concepts through the antics and discourses attributed, for example, to a rabbit. Carroll’s and Kiplings’ works continue to enjoy a wide readership, but neither holds a candle to the popularity of the human-like portrayals of mice that took place in the first half of the century that followed.
In the early years of the 20th century, merchandising based on loving, friendly, and heroic rodents became a huge money maker, not only for the entertainment industry but for toy makers as well. Consider, for example, the lovable characters Mickey and Minnie Mouse, created in 1928. Since then those characters have produced $billions for the Walt Disney Company, not to mention firms like Fisher-Price that make toys based on them.
The Mickey Mouse Club, a popular American variety show, aired under various names on television from 1955 to 1996. It featured mostly teenaged stars and its targeted audience ranged from the very young to the very old. Viewers were invited to join the club and become actively involved in it. Many did, and — for a significant fraction of those — the experience changed their lives in ways reminiscent of a religious awakening.
We’d be remiss if we neglected to mention that fearless righter of wrongs known as Mighty Mouse. Created in 1942, the year one of the authors of this paper was born, Mighty Mouse debuted in the short film “The Mouse of Tomorrow” as Super Mouse, retaining that name until the 8th film, in 1944, when the moniker was changed to Mighty Mouse. Like the Mickey Mouse Club on a smaller scale, the Mighty Mouse Playhouse debuted in 1955 as a Saturday morning cartoon show that popularized the character far more than the original theatrical run. The Mighty Mouse Playhouse continued until 1967, and was revived in various forms through 1989. Its catchy theme song, “Here I Come to Save the Day!” was so popular that most of the kids (not to mention the adults) who regularly watched the Saturday morning episodes could recite the words of several versions (all produced by Mitch Miller and his Orchestra) from memory.
It is not hard to see how these and a host of similar memes have helped nurture a positive view of rodents in general. It is not at all surprising for the authors to meet elderly men and women whose fondness for rats and mice have led them to tolerate, and even celebrate, the presence of these animals in their homes. Usually, it is the younger members of these folks’ families who initiate the service call to “fix” grandma’s or grandpa’s rodent problem. All too often, however, that work is doomed from the start. If grandma or grandpa refuse to stop feeding their furry friends, and won’t allow them to be trapped, almost nothing can be done.
Much of one of the author’s formative years were spent in the 1950’s, the heyday of the Mickey Mouse Club. In fact, Annette Funicello, who in his humble opinion was definitely the prettiest of the mousketeers, was one of his earliest heart-throbs. Thus he finds it easy to sympathize with the deep feelings of affection many have for those well-known but fictional Disney characters from the rodent family. At the same time, though, it is generally best for fiction to be recognized as such. Sadly, those who cannot differentiate between fantasy and truth may pay a heavy price in the bargain.
So, let’s bring this discussion back down to earth… Hardened, practically pathological cases of rodentiaphilia do exist, but they are somewhat rare. Less serious cases are much more common, and the authors meet with people of all ages on a regular basis with people whose thought processes are influenced by at least some amount of rodentiaphilia. For the average, not-too-fanatical rodentiaphile, we’ve learned, it’s ok if rats and mice are in their yards and alleyways, even if present in large numbers. All that is needed is to keep them out of their homes and places of work.
Though no serious epidemiologist would agree with that assessment, we all have our passions, and some are harmless while others are so ingrained as to appear to be practically impervious to logic, even when carried to an extreme that can only be termed pathological. For those who prefer to ignore reality to their hurt, rodentiaphilia — when applied to the point that wild rats and mice are permitted to live in close proximity to humans — can be a recipe for disaster.
This short discussion emanates from the authors’ fervent belief that even pathological rodentiaphilia is curable. The cure, though, must begin with an honest assessment of the risks that such a mindset engender.
The Truth about Wild Rodents and Human Health…
In 2008 Bobby Corrigan, PhD., who is an expert rodentologist based in New York City, published an illuminating article titled “The House Mouse as a Potential Health Pest in Homes and Apartments,” in Pest Control Technology (PCT) magazine. There he describes a list of morbidities that humans suffer from mouse infestations. What is most interesting about these mouse-borne diseases is that most people never see the connection between them and the mice in their homes. It is easy to be a rodentiaphile if nothing in your everyday experience indicates that rats and mice are causing you harm.
For example, Corrigan reported that 18% of asthma sufferers test positive for Mouse Urine Protein (MUP) sensitivity, but most are misdiagnosed as allergic to pollen, dander or “something in the air” and don’t realize that their asthmatic episodes would be reduced or eliminated if their abodes were free of mice and the urine those animals so effectively disperse within the areas they visit.
This is an important but mostly unheralded fact: mice are among the most incontinent mammals known. Unlike most animals, they do not store their urine internally, waiting until it is convenient to release a copious stream at once. Instead, they urinate in micro-droplets constantly. This means that when mice take up residence in a home, that home will soon have lots of small amounts of mouse urine, spread all over the place.
Further, MUP does more than cause asthma. Skin contact with mouse urine by sensitive individuals causes rashes, itches, and sensations that they are being attacked by fleas, bedbugs, or mysterious mites.
Another example mentioned by Corrigan is lymphocytic choriomeningitus (LCM), caused by a virus (LCMV) that is transmitted to man via rodent urine and feces. In humans, LCM presents with symptoms that mimic those of the flu — headache, fever, and muscle pain — and most symptomatic victims assume that’s all they have. About 20% of LCM cases also result in meningitis (inflammation of the brain and spinal cord), and in most of those cases the symptoms are mild; more severe cases, however, lead to fatalities 2-5% of the time.
10 years later (2018), Corrigan published an article on the “Public Health Importance of Urban Rodents,” again in PCT Magazine. In that article, he relates the results of an in-depth study of the pathogens carried by 416 wild mice trapped in New York City. The research was conducted by a team led by Simon Williams, a research scientist with the Columbia University laboratory run by Ian Lipkin, PhD, whose research on West Nile virus and SARS earned him worldwide acclaim.
What the analysis of the 416 wild mice William’s team trapped showed was that their droppings, urine, and bodily tissues harbored at least five bacterial pathogens and one protozoan parasite with significant frequency. Ingesting any of these, either directly or indirectly by contact or inhalation, produces sicknesses ranging from mild annoyances (diarrhea, stomach cramps, vomiting) to life-changing and life-threatening diseases.
The protozoan parasite William’s research found in these mice was Toxoplasma gondii, the agent causing toxoplasmosis. Cats are the definitive host for this parasite, but they become infected with it by killing and eating infected mice, and cats and mice spread the parasite to humans. Pregnant women who become infected often suffer spontaneous abortions; infected babies carried to term may suffer fetal abnormalities such as brain damage, early childhood death, and permanent retinal damage leading to partial or complete blindness in one or both eyes.
Much more could be posted here regarding the effects of T. gondii infections and infections from the other pathogens found by William’s team in the mice they analyzed, but you get the picture. If everyone did, we’d all work harder doing all the things only homeowners can do to keep mice and rats at bay. For another, we’d stop thinking that as long as our pest control provider puts a few black boxes around our home, and promises to service them regularly, our rodent worries are over.
Rats, Mice, Contamination and Disease…
The short story: Rats and mice contaminate the food people eat, and carry parasites and diseases that negatively impact the health of all the humans and pets they come near.
It is now confirmed that rats and mice carry and spread up to 55 different diseases that affect humans and our companion pets. That number sounds high, and some will think that referring to it borders on, or actually crosses the line into, sensationalism. Supporting that thought is the fact that the above study by Simon Williams in NYC reported only 6 diseases in those mice. Other studies indicate that specific rodent-borne diseases (1) tend to be confined to limited geographic areas, and (2) are only carried by certain species of rodents.
There is some truth to both of the above suppositions. Still, there is also a lot of gray to go with the black and white. For many years the authors have witnessed and studied the amazing ability of rats and mice to carry large numbers of disease pathogens at once. That’s sobering, to say the least. Over that time we’ve only seen the number of confirmed diseases they carry go up, rather than down. As time goes on, chances are that many more diseases vectored by all species of rats and mice in most or all locales, will be discovered. As a result, it seems doubtful either of the suppositions cited above will bear out in the long run.
Consider just one example: It was initially believed, when hantavirus first “surfaced,” that it was confined to the Four Corners region, where southeastern Utah, southwestern Colorado, northeastern Arizona, and northwestern New Mexico meet. That’s where, in 1993, an outbreak of hantavirus infections caused the first known human cases, many of which were fatal. Supposedly, this was a novel virus that had never before been encountered, yet genetic analysis eventually showed it had been around for centuries. Further, by 2014 scientists had found a long list of related hantaviruses that were carried, not only by mice, but by shrews, moles, and bats.
Four Corners is an area renowned for its desert-like geography and its dry, hot climate, all of which are perfect conditions for the mice that carried the hantavirus figuring in those cases. Yet, in the 24 years that followed — from 1993 through 2017 — a total of 24 Texas counties, including Harris, Jefferson, Travis, and Tarrant, whose climates and geography aren’t remotely like that of the Four Corners region, recorded 45 hantavirus infections. Of those only six victims had an out-of-state exposure.
The above map was published by the Centers for Disease Control and Prevention, in a report titled “Hantavirus Disease, by State of Reporting.” That report stated that “As of January 2017, 728 cases of hantavirus disease have been reported since surveillance in the United States began in 1993. These are all laboratory-confirmed cases and include hantavirus pulmonary syndrome (HPS) and non-pulmonary hantavirus infection.”
Regarding the second supposition, it has been commonly stated that (A) only four species of rats and mice are natural hosts of the hantavirus pathogen, (B) not one of those species is commonly found near human habitations, and (C) victims of hantavirus only become infected after having frequent contact with infected rodents and their droppings in homes and workplaces. Research conducted over the recent past has called into question all three of these assumptions.
Deer mice and hispid cotton rats, for example, though most at home in rural meadows and woodlands, often invade rural homes and urban residences. All they need is a plentiful supply of food, water and shelter to get them to nest, reproduce, and become part of the ecosystem. Furthermore, many more than the four “usual suspect” species carry hantavirus. Research on that question, presently continuing, has already uncovered three more Texas rodent vectors. If history is our guide, the likelihood that other rodent vectors exist today, and that even more will become vectors in the future, is relatively high.
Dangers to cats and dogs…
As mentioned earlier, cats that kill rats or mice risk catching serious diseases if they eat what they catch. Even if they don’t eat them, during the killing event and later, while transporting the dead rodent to the family doorstep (many cats that don’t eat their kill still proudly display their accomplishments at the front door or on the back patio) they become exposed to all the ectoparasites infesting the rodent’s body.
When the family dog sniffs out a rat or mouse nest or dead body in the yard, the same thing happens. Before long, the whole family becomes exposed to these same diseases and ectoparasites when in the process of cuddling with the family pets.
Once a rat or mouse gets inside the home, all these risks multiply.
Rats and Mice are Everywhere, and so are Their Food Sources…
Though we rarely see them, rats and mice are common features in all our neighborhoods. Subdivisions with extensive storm sewers exacerbate the problem because the underground network of concrete pipes that — like natural caverns — maintain a nearly constant temperature, provides rats, mice, and a host of other wild animals with a balmy subterranean superhighway within which to travel all over the subdvision entirely unseen, throughout the day, and throughout the year.
It doesn’t matter, though, if the setting is within a wilderness, an urban, or even a suburban one. We cannot keep rats and mice out of our yards all the time, no matter where our home is located.
This is why the author, when discussing rodent control with others, stresses how most of us get it wrong when we think about the way it should be done. When a residence or business “falls victim” to a rodent infestation, common wisdom nearly always prescribes an event-mediated solution. In other words the emphasis is on quickly exterminating the existing infestation so the site can revert back to the “previous no-infestation status quo” that most presume to be the natural state for that site.
This widely-accepted approach — which prevails today, even within the pest management industry — suffers from two misunderstandings. First, the importance of achieving a quick solution is way overrated, often with disastrous results. “Haste,” said John Heywood way back in 1546, “makes waste.“ Actually, that’s the shortened version of what he wrote in his glossary of English proverbs: “Som thyngs that prouoke yong men to wed in haste, Show after weddyng that haste maketh waste.”
Today, some 574 years later, his words in both versions still ring true. When it comes to rodent control those words have never been more relevant. Rodent infestations neither develop in a flash, nor are properly cured that way. Rats can only collect, nest, and breed in collective groups when a narrow set of predisposing conditions exist together. Those conditions must be identified and nullified as part of the control process, or what appears to be control soon proves to have been a mirage, as fresh rodent infestations emerge with a vengeance. That process takes both time and energy.
Second, the presumption that a no-infestation status quo is a natural condition for any site in Texas — or, for just about any place in the United States, for that matter — is based on a specious myth. Specious is the right adjective to use here, because it defines something that has a false look of truth and legitimacy. In this case that false look of truth is bolstered by our natural tendency to grasp anything that looks like a silver bullet remedy and cling to it if our immediate experience seems to grant it validity.
After all, you never noticed any rats before the infestation started, right? For years, maybe, you never noticed any. So, you say, let’s just get rid of these newly arrived ones so we can go back to “the way it was before, rat-free.” The problem is, the rats were there all along, whether you noticed them or not. And once you wipe out the rats causing the infestation that presently feeds your angst, the rest of the rats in your environment will still be there. Why is this so?
A true story: A gentleman from California recently moved to Austin with his wife and young son. The home they purchased was spacious, and was perched on the side of a hill overlooking a beautiful valley. He called one of the authors to set up an inspection. “There aren’t any existing pest issues, but I’d like to have you check for possible future problems that might be preventable,“ he said.
The inspection found lots of vegetative features in the landscaping perfect for rodent habitat, a fountain in the back yard that supplied water to foraging animals 24/7, and a host of botanicals with fruits, nuts, and buds that rodents love to eat. As the back yard progressed up the side of the hill, it eventually disappeared in thickets of thick undergrowth, shrubs, and native trees.
“You have rodents in your yard,” the author quietly told him. “But,” he gently protested, “I don’t see any evidence of that, and I’ve never seen any in the three weeks we’ve lived here.” Well, came the reply, “they’re here, but they don’t come around when you are up and about, Rodents don’t want you to see them, because once you do you’ll take steps to make their lives miserable.”
He grinned, and shook his head in disbelief, but the author conducting the inspection had developed a mutual trust with him, and — seeing wisdom in shelving his skepticism for the moment — he agreed to have a set of E2M2C™ stations placed around the perimeter of his home anyway, just to be on the safe side. When they were first inspected, not long afterward, he was amazed at the amount of rodent bait that had been consumed. Two were completely empty. Actually, that’s the typical scenario for E2M2C™ station placements, no matter where they are placed.
One more true story, before we move on:
The owner of a professional office building in Round Rock, Texas, had the structure built on stilts next to an old established riverbed. Over the past fifteen years the building was constantly plagued with rats. It was obvious to him why this was so, given the surroundings dominated by a riverbed, the wilderness that came with it, and the nearby businesses that had dumpsters overflowing with edible garbage.
He asked what could be done to fix the problem. A set of E2M2C™ stations was placed at the site, which brought the existing infestation to a halt immediately and, as long as they were regularly serviced, pretty much kept it that way (there is more to this story, though, which is shared below.)
Impressed, he asked if the same stations could be placed at his residence, 17 miles away in downtown Austin. “We’ve never had any rats or mice there, in the 22 years we’ve owned that home,” he said, “but we don’t want to ever get any. So, just the bare minimum number of placements should give us excellent protection and peace of mind.”
Never had them? We didn’t press the issue, but knew from experience what to expect…
On the first inspection one station was 90% emptied of bait, and the rest were completely empty. So we doubled the number of placements and are now servicing them once every four months. This client is now virtually freed of a problem he and his family never knew existed, and all are healthier as a result, in ways they never imagined.
Now, there is more to this story that we need to share with the reader… The business built on stilts over a generally-dry riverbed is, statistically speaking, an outlier. It has had to be serviced more often than is typical for a building of that size. Currently, if we don’t service it every month, newly arriving rodents from the surrounding area show up in such numbers they deplete the bait in the E2M2C™ stations so fast that some don’t get a seat at the table and survive long enough to get back into the business building and start making noises in the ceiling.
We place wildlife cameras at outlier sites like this, to monitor what is going on in an effort to discover why its outlier status persists. We know there isn’t any food available to rodents inside this building, and none on the exterior as well. Furthermore, there is no habitat for nesting purposes on the exterior of the structure or in the yard. Therefore, all the rats that get into this structure come in for only one purpose: to loiter, nest and, if they are not quickly neutralized, to multiply.
One thing we’ve learned in our research is that, contrary to what many rodent biology experts assert, commensal rodents only nest in man-made structures when they cannot find suitable natural habitat nearby. The lure of this structure is not so much its native “lure” as the absence of natural habitat in its immediate vicinity. Yet, we could not find any ground-level or near-ground-level enty ports that could be exploited by rodents seeking to get into the building, either. This meant we had no choice but to “go to the mattresses.“
That meant, for rodent control at this site, that we had to go aloft to find and seal all the rodent access ports we could find. We usually don’t do that unless absolutely necessary, for reasons we explain earlier. Here, we had no choice.
Rats in Your Yard, Not a Problem?
Rats don’t have to get into your home to make you sick. As long as they are spending time in your yard, on the porch, at the front and back doors and on the patio, dropping their fecal pellets and urinating constantly the way rodents do, you and your family risk catching one or more of the diseases they carry.
But, as with many of our clients, you won’t see them most of the time if at all, despite the fact they are present in large numbers. And, as Corrigan pointed out in his 2008 paper, when you get sick from the pathogens those rodents bring to your home, you won’t have any idea that a rat or mouse was to blame…
Lesson: They’re everywhere…
Rats and mice are so plentiful in most environments that they pay regular visits to practically every square inch of all the surfaces accessible by them. That is one of the main reasons why rats and mice are considered among the most successful terrestrial mammals on planet earth. Another key to their success is their ability to stay out of the lime-light. Rats and mice typically don’t come out during the day, and even when they come out at night the slightest noise will send them scurrying into the closest hiding place they can find.
But let’s analyze the truth about the two aforementioned misunderstandings in even greater detail. To do that we need to consider rodent activities in wilderness, urban and suburban settings. And we need to become familiar with the nuts and bolts of rodent biology.
Homes in Wilderness Retreats…
Wilderness homes surrounded by forests or meadows are set in the midst of just the kind of habitat in which rodents thrive. Texas is home to 68 different species of rodents, and 24 of these are found in Central Texas (see appendix B, at the foot of this paper, for details on each of these species of rodents). Most (all but three) are native rodents that are not commensal, i.e., they don’t have a particular affinity for humans and may even prefer, as a rule, to avoid areas of human habitation. They do carry diseases that affect humans, however.
Forest trees produce nuts and seeds that rodents eat and store away for rainy days, so our native rodents that forage there are never fully deprived of sources of sustenance. Meadows produce seeds and buds that are similarly eaten and stored for times when such foods are scarce.
When a home is set in the midst of such wilderness areas, the native rodents that were there before the home was built are now provided with a panoply of new and novel food sources. They are not shy about taking advantage of those sources. Obviously, such homes are prime candidates for a serious rodent control program, one that not only deals with any rodents that may already be nesting and foraging near the home, but that also deals quickly and decisively with any that happen to wander in, from time to time, from the nearby meadows and forests.
Commensal rodents — the common house mouse (Mus musculus), the brown or Norway rat (Rattus norvegicus), and the black or roof rat (R. rattus) — are often absent at such homes. They do not usually wander far from places of human habitation, so they have to be brought in. That’s not too hard to do, and it usually happens without the knowledge of the person or persons who transport them there in bales of hay or foodstuffs picked up and delivered from areas where commensals are found in large numbers. Once they arrive, they become dominant, but until that happens the native rodents from the surrounding forests and meadows dominate.
The authors have studied a number of such wilderness locales in Texas where no commensals could be found. These locales still hosted a wide variety of native rodents. Rice rats, hispid cotton rats, voles, and various species of native mice were abundant.
One ranch home outside of Coupland, Texas, for example, hosted large numbers of native rodents that were nesting in the barn and in the crawl space under the 1890’s era Texas Victorian residence nearby. A species of kissing bug (Triatoma gerstackeri) had infested the rodents — which happened to be hispid cotton rats — that were nesting under the residence.
The kissing bugs infesting the rats entered the home’s living space through gaps in the flooring and, at night while everyone else was asleep, they attacked the home’s human and canine occupants. Kissing bugs are fairly large insects, but their saliva deadens the bite wound so the victim does not feel any pain. Bugs infected with the Chagas disease parasite (Trypanosoma cruzi) are capable of transmitting that parasite to humans.
Another large ranch residence, situated in the midst of a 25-acre tract east of Georgetown, Texas, was found to host large numbers of commensal rats and mice. These evidently had been bought in, inadvertently, from urban locations. When the author was called in they were the dominant species on the ranch. Most were nesting near the ranch’s large horse barn, where they fed on stored horse feed, and littered the floor of the entire barn with their fecal pellets and urine.
A set of E2M2C™ stations was placed around the perimeters of the home and the horse barn, then inspected 30 days later. Unfortunately, at this ranch — which was bordered by the San Gabriel river — the raccoons were huge and hungry, and during that first 30 day period they were found to have rifled through all the E2M2C™ stations. This sometimes happens in urban settings as well, and the remedy is the same regardless of the setting: the standard E2M2C™ stations must be replaced with raccoon-proof versions.
That was done at this ranch, then checked again 30 days later. This time the raccoons had left them alone, but the commensal rodents had practically wiped out the stations’ rodenticide provisions. 30 days later the stations still contained about 50% of their rodenticides, so the inspection interval was lengthened to 90 days. On that inspection, less than 10% of the rodenticide had been consumed. This signaled that the dominant commensal rodents had now been fully nullified. When this happens in a wilderness area, the resulting vacuum does not remain for long, but is eventually filled by native rodents.
It takes weeks or months for the native rodents to resume foraging in territories where commensal rats — which are much more aggressive — had previously held sway. At this ranch, on the next service event, performed four months later, more than 50% of the stations’ rodenticide provisions had been consumed. The native rodents had returned, and now the E2M2C™ stations were hard at work keeping them under control.
Some may question if it is necessary to control native, non-commensal rodents at homes, barns, and other out-buildings in wilderness settings. A partial answer is provided by the first account in this section, where a ranch home near Coupland, Texas, was found to be infested with hispid cotton rats infected with triatomid kissing bugs. The family living at this home was being attacked nightly by these blood-sucking insects, which placed them at risk of catching Chagas disease. That disease was not the only risk these folks faced, however, because our native rodents are known to be direct vectors for a long list of other diseases — including hantavirus — as well.
Not only are infestations of native rodents dangerous because of the diseases they carry, but they attract other animals that prey on them. At the ranch outside Coupland, for example, a huge western diamondback rattlesnake (that the author estimates was in excess of 5 feet in length) was observed near the home’s skirting on one of the first visits there; this large, clearly well-fed reptile was evidently getting plenty of nutriment from the maternity nests of the interloping hispid cotton rats. Later, several juvenile rattlesnakes were also found in the home’s yard. An important key to keeping such snakes out of residential yards, whether in urban, suburban, or rural settings, is to bring their favorite prey — native or commensal rodents — under full control.
Homes in Urban and Suburban Neighborhoods…
Homes in typical urban or suburban settings usually provide rats and mice with a multitude of food sources like bird feeders, pet food, unsealed garbage containers, flower garden seeds and fruits, and pet scat. In such settings, even strenuous rodent control efforts — using traditional control devices carried out at a single home in the neighborhood — may be utterly frustrated by a lack of such control efforts on the parts of their neighbors.
Fortunately, even in the midst of such settings the E2M2C™ program achieves and maintains control as long as the primary residence there practices strict nutriment control by avoiding the use of traditional bird feeders, cleaning dog and cat feeding dishes immediately after pets have had their fill, and regularly removing pet scat.
The pressure on such homes from surrounding hot spots of commensal rodent activity can be quite high, however.
In many neighborhoods are often found kind souls whose fervent avocations involve feeding all the wild animals in the subdivision. Such individuals have been known to take great pleasure in placing dishes of peanuts, piles of sunflower seeds, pieces of raw and cooked meat, and a variety of other kinds of food, in their back yard several times a week. Some put out the food and go about their business, while others retreat to the back porch to watch the wild animals arrive in droves to take part in the bounty.
An acquaintance of one of the authors is an experienced and well-respected physician. He and his wife buy several 50-lb. bags of dry dog food every week. Several times in the coming week, just after the sun sets, they pour the contents of these bags out on the ground, about 50 feet from their home. Hundreds of raccoons immediately pour out of the nearby woods and mill around their feet, greedily consuming the dry pellets. It is an amazing sight to behold, and this physician and his wife seem genuinely mesmerized by the spectacle.
Over the past thirty years the author involved has discussed the negative issues associated with this practice with his friend in detail. Laying out the obvious problems has never been persuasive, though. He and his wife just smile, wholly unmoved. That’s an important point to ponder. These two are among the finest individuals this author has ever known — their peculiar raccoon-feeding habit notwithstanding — yet they refuse to acknowledge the unhealthy dependency they are inculcating in the raccoons, and the growing rodent populations they are husbanding. Sadly, they are not alone.
When the authors are called to homes with serious rodent infestations whose yards are entirely bereft of rodent attractants, these friends come to mind. Inspecting further usually uncovers a neighbor’s yard serves as a feeding ground for rodents.
The majority of those who intentionally feed wild animals in their yards know their behavior is not good, either for the wild animals they feed or for their neighbors, yet they do it anyway for the pleasure it gives them. A few others have nothing but positive feelings about this dangerous practice. Perhaps they feel their professions and avocations are so naturally connected that they cannot imagine separating the two. Many — like our good friends in East Texas — are absolutely unwilling to even consider abandoning the practice of feeding wild animals in their yards. When made to stop doing so openly, most continue to do so surreptitiously, putting food out after dark. In almost every case we’ve followed, when an offending neighbor is challenged, stealth feeding commences. Such is the depth of their dedication to the art.
The point here is not to cast aspersions, but simply to illustrate that it is common to have open and stealth feeding of wild animals in many if not most neighborhoods in America. The practice is rooted in deeply felt beliefs that are not amenable to change. For that reason, it is reasonable to believe that any home in an urban or suburban setting will face a constant barrage of rodent activity emanating from unseen, uncontrollable portions of the surrounding homes. Even if open and stealth feeding of wild animals is not taking place, however, other conditions common to many yards still provide wild rodents plenty of nutriment, particularly if pets are involved.
Pets are often fed outside. Some homeowners are very disciplined about cleaning up the feeding area and withdrawing the feeding bowl every night, before dark. Others, though, leave the feeding area littered with food items and even fill the dog’s bowl before retiring. Some pet owners see “wisdom” in using “on-demand” dog feeders, which dispense dog food whenever the pet pushes its muzzle into the food container. These undisciplined pet feeding practices invite rats and mice to the table in large numbers. Sadly, many disciplined pet owners are surrounded by neighbors whose lack of discipline essentially negates theirs. But there’s more to pet issues than undisciplined pet feeding methods.
Dog scat, which contains significant fractions of partially digested carbohydrates and proteins, has been implicated in attracting and feeding rats and mice. It should be mentioned, though, that some folks have exaggerated the importance of dog feces as a source of rodent food. Often, such exaggerations are published by those engaged in the business of cleansing yards of dog for a fee. One such business asserts in its Internet ad, for example, that dog poop is the primary food source for urban rodents. That claim is of doubtful veracity. Contrary opinions are also plentiful, including blatant assertions that rats and mice never consume canine scat. The author, however, often finds clear evidence that rodents feed on canine scat.
Nobody disputes that an abundance of odorous dog feces in a yard will attract rodents to that locale. Avoiding conditions that attract rodents should be high on the list of all homeowners, so whether or not the particular attractant is later included in the rodent’s food chain is all but moot. Yet, once rodents arrive, it is also possible that the feces itself will become part of the rodent’s diet, especially if those rodents are deprived of their preferred sources of food. This can occur when the pet owners, though deficient in their disposal of pet feces, are careful not to leave their pet’s food out overnight.
Food Service Businesses…
Businesses that produce edible waste disposed in ordinary dumpsters can support large populations of rodents. As these populations grow, the rodents regularly migrate to the surrounding neighborhoods in search of less-contested food sources and safer nesting spots to raise young.
It is obviously incumbent on such businesses to follow a strict sanitation protocol regarding their edible waste disposal. Some are quite good at that. Others not so much. It isn’t easy to train staff to follow good sanitation practices, but it must be done, in a never-ending program reinforced on a daily basis. When a dumpster or compactor area is allowed to become unsanitary, the store’s customers are led to wonder if the kitchen is as sanitary as it should be.
Just Passing Through?
When a rodent simply passes through our yards without loitering or nesting there, the risks mentioned above are reduced. To keep those risks as low as possible, homeowners and business owners must do all they can to eliminate rodents food sources and habitat they can use to nest and reproduce.
When done right, rodent control is not a one-time, or even a multi-time event. Instead, it should be conducted as a well-orchestrated, carefully planned and conducted process, whether the site is a small residential home or a huge commercial, industrial, or academic campus. The author has learned, in the course of rodent control work done over many decades, that this process includes multiple functions.
Unsecured rodenticides accessible by children and pets have been prohibited by law throughout the U.S. for years. As a result, most rodent extermination projects begin, today, with the use of secure child and pet resistant bait boxes. Those boxes, though locked in a way that make it difficult or impossible for children, dogs, and cats to access their bait supplies, have rodent-friendly ports that rats and mice can use to gain ready access to the box’s rodenticide provisions.
Some rodenticides are not lethal to their rodent targets until multiple feedings have taken place; the poisoned rodent continues to feed, several times a day, and generally succumbs to the poison in 4-10 days. Others are lethal on a single-feeding event; the poisoned rodent usually succumbs — generally within one to four days afterward — without needing to feed more than once.
Of these latter baits, some tend to cause the rodents to lose their appetites so that, after a single meal, they stop feeding altogether; this “stop-feed” effect helps protect animals that may later consume the poisoned rodent, by limiting the amount of rodenticide that the poisoned rodent contains. Other single-feed rodenticides have no effect on appetite, leading their rodent targets to consume many times the lethal dose.
Only rodenticides that have a stop-feed effect on the rodents that consume them are used with the E2M2C™ program.
There is No Shortage of Rodent Bait Stations on the Market…
A wide variety of child and pet resistant rodent bait boxes are currently in use in the United States. These include the following examples:
- Bell Labs PROTECTA Bait Station
- Bell Labs PROTECTA EVO Ambush Bait Station
- Bell Labs PROTECTA EVO Circuit
- Bell Labs PROTECTA EVO Express
- Bell Labs PROTECTA EVO Landscape
- Bell Labs PROTECTA EVO Weighted Landscape
- Bell Labs PROTECTA LP Rat Bait Station
- Bell Labs PROTECTA Sidekick Tamper Proof Rat/Mouse Bait Station
- B&G Rodent Bait Station
- JT Eaton 902R Top Loader Bait Station
- JT Eaton 904H Gold Key™ Rat Depot™ Plastic TR Bait Station
- JT Eaton Rodent Rock™ Rodent Bait Station
- Lipha-Tech Aegis™ Rat Bait Station
- Lipha-Tech Aegis-RP™ Anchored Rodent Bait Station
- Lipha-Tech Aegis-RP™ Rodent Bait Station
- VM Products EZ-Clean™ & EZ-Secured Rodent Bait Stations
- VM Products EZ-Versa™ Rodent Bait Station
Though the above list is representative, it is not exhaustive. The total number of different rodent bait boxes being sold in the United States is several times times that listed here. One might consider this to be strong evidence that the science of rodent baiting is healthy and up-to-date. Nothing, however, could be further from the truth.
According to a 2019 article in Pest Management Technology Magazine written by Sandra Kraft and Larry Pinto, selection of a bait box for your particular needs is a complicated issue. Worse, though most on the market claim to be tamper-resistant, Kraft and Pinto point out the following:
“The stations must be lockable with a key or other device and they must be sturdy enough to resist crushing or breaking. Further, to be considered truly tamper-resistant, the station must be anchored and secured. It can be staked to the ground, nailed to a surface, chained or cable-tied to a fence, beam, wall, pipe, or other support. It can also be anchored by securing it to a heavy base such as a patio paver block; some stations come with an anchoring base already installed.” Source: Sandra Kraft & Larry Pinto, Why PMPs Use Rodent Bait Stations.
One thing Kraft and Pinto neglect to mention is that many, if not most rodent bait boxes on the market today are easily opened simply by dropping them, so flimsy are their locking mechanisms. By perusing the manufacturer’s sales literature (click on each of the above links to do that) one easily discovers why this is so. Today’s bait box designs focus heavily on enabling service technicians to open them easily and quickly. A single lock on each box is advertised as a plus, as is ease of opening the box for servicing. This focus recognizes that bait boxes that are not easily and quickly opened for servicing don’t get serviced with regularity, if at all.
There is another fact about rodent bait box servicing, too: rodent bait box maintenance is one the nastiest, and riskiest tasks pest management technicians perform. It is nasty because the typical bait box tends to be clogged with wet, soggy, rotting and putrefying bait, rodent feces, rodent nests, insects and rodent parasites. The job is also risky, because once the bait boxes are opened the technician is exposed to all that nasty stuff and — if it is handled the wrong way — it can sicken the technician and, by extension, his or her family.
Combine these facts with another important point: the technician knows that the clients at whose sites where the bait boxes are located either do not have keys to open them or, even if a key is available, the likelihood the clients will open them is practically nil. Translation: there is almost no risk to the technician if the bait boxes at his or her clients’ sites get skipped. Sometimes they are never serviced at all, after they get placed, until the client complains that they are noticing rats or mice in the yard or inside the home.
The author has a set of bait box keys that open practically every device on the market. By opening up the rodent bait boxes found in the field, one learns a lot about the kinds of bait being used and how the bait boxes are being maintained. What is mostly found, unfortunately is a nasty interior with either no bait at all or soggy, rotten bait that is so polluted with moisture, mold, mildew, and other contaminants that no self-respecting rodent would dare touch it, much less have it for lunch.
A host of other negative issues also surround the design, management, and maintenance of all the rodent bait stations, in their stock conditions, that the author has tested. Even those that are truly hard to accidentally open tend to suffer from an opposite kind of problem… they’re too hard to open. In some cases the bait box’s locking mechanism deforms over time so the keys stop working. In others, the keyways are easily clogged with airborne dust and debris to the point that the bait box keys can no longer be inserted deeply enough to unlock the box.
In practically all of the bait boxes the author has tested in the field, once in place for more than a year the utility of the box as a means of dispensing rodenticides is usually so compromised by a long list of environmental factors that the bait box is essentially useless. In many cases this occurs because, at the site where the box is placed, weeds, leaves, dirt, and debris completely occlude the ports used by foraging rodents to gain access to the rodenticide the box contains.
Those and other issues are among the least recognized and understood problems confronting today’s rodent management industry. Though hundreds of thousands of rodent bait boxes are being used all over America, practically all of them are inadequately designed, badly mismanaged, and poorly maintained.
So, Commensal Rat and Mouse Populations are Still Exploding…
As a direct result of all this, populations of commensal rats and mice are thriving in places where they are likely to do the most harm, and the lives and well-being of raptors are being placed in jeopardy by the injudicious use of bio-accumulative rodenticides. Populations of commensal rats and mice are exploding in our neighborhoods. They overrun our dumps and waste management facilities. They threaten to contaminate our foodstuffs, utensils, and the surfaces on which we prepare and serve food in our homes, restaurants, food processing facilities, hospitals, and nursing homes. Because the associated dangers are underestimated, while most efforts to deal with them are largely ineffective, the rodents often get away with doing all of those things with impunity…
But who knew?
Well, if you live in certain parts of Chicago, New York City, or any of the several other urban areas where rats are seen and are in the news daily, you probably do know. But, outside of those and similar locales, concerns about rats and mice are generally given short shrift. The vast majority of America’s citizenry thinks rodent control is not a big concern. Compared with all the other worries most people have, rats and mice are way down on the list.
For example, one Internet listing of the 10 worst pests in the world, published by a highly respected pest control company in Houston, Texas, begins with, as #1, the Asian Tiger mosquito, and ends with bedbugs as #10, without even mentioning rats or mice, despite the burgeoning population of rats in the Houston metropolitan area. Another listing of top 10 pests, published for pest control technicians, places house mice #6, without mentioning rats at all. True, a few contemporary listings of pests do put rats and mice at or near the top of the list. Yet, overall, spiders, scorpions, mosquitoes, and ants are considered — by the majority of people on the street who are asked — to be much more scary.
Does that make sense? Absolutely not, for a number of reasons. Were humans more cognizant of the risks posed by rodents to their health and that of their loved ones, they would be genuinely alarmed. It is not a stretch to assert that one of the most important keys to maintaining human health is a program of serious, consistent rodent control in our neighborhoods, cities, farms, and workplaces.
How the EntomoBiotics E2M2C™ Program Achieves that Goal…
The EntomoBiotics E2M2C™ program marries two processes. One of the most important of these is the day-to-day management of the site’s general environment, in a way that lessens the attractiveness of the environment to rats and mice. That process is the responsibility of the site occupant, be it a homeowner or business manager. Each site has different set of specific requirements, based on the site structure, its surroundings, and the day to day activities carried out there. In some cases the list of requirements is lengthy, but for others it is confined to only a few items.
How well the requirements placed on the site manager are carried out has a major impact on the second process, which involves the placement and servicing of E2M2C™ stations. The devices presently in use are based on one or more of the stock rodenticide dispensers listed above that have been specially modified to conform to a set of proprietary E2M2C™ standards. Those standards were chosen to maximize safety, durability, and utility, and require significant architectural changes to the stock device. Once modified, the E2M2C™ station is able to withstand rough handling without opening up, and harsh environmental conditions without compromising the quality of the bait products it contains.
Each E2M2C™ station is also clearly tagged, on its exterior, with a printed notice showing the date when it was last serviced. Thus, the client can tell by inspecting the station’s exterior when it was last serviced.
Indeed, because every E2M2C™ station is at least triply locked, even if the client has a key it cannot be used alone to open the station in the field. Defeating all the added locks attached to the E2M2C™ station is not an easy task. In fact, even the service technicians that interface with placed E2M2C™ stations in the field can’t open them at their placement sites.
Does that make sense? To the E2M2C™ program it does, because one of that program’s important features is that it requires that each station be fully cleansed of rodent urine, fecal pellets, insects, mites, ticks and fleas as a first step in the servicing process. EntomoBiotics Inc. does not believe it is good for our E2M2C™ clients to have contaminated E2M2C™ stations at their sites any longer than necessary.
Imagine this: rats and mice visit the E2M2C™ stations at your home and business and, while eating the bait inside it, they defecate and urinate. When they leave, the fecal pellets and urine are left behind, along with any mites, fleas and ticks that jumped off their bodies while they were eating. We always advise our clients not to touch or handle the E2M2C™ stations at their homes or businesses for this very reason.
So, at every service interval, the in-place E2M2C™ stations are swapped out with fresh ones that have been cleansed, sanitized, and re-provisioned with clean bait products at the EntomoBiotics Lab. The used station is sealed in a plastic bag along with a cotton ball saturated with ethyl acetate. The ethyl acetate evaporates in the plastic bag, producing an atmosphere in the bag that neutralizes any insects, mites, fleas, or ticks that rodents may have left behind. When the EntomoBiotics Inc. laboratory technician opens the bag later, this process prevents exposure of the technician to live ectoparasites.
At the lab, before doing anything else, the laboratory technicianb sprays the outside of the station with a CDC-approved sanitizing solution, to the point of run-off, that kills any bacterial or viral pathogens lingering there. On removing the E2M2C™-mandated auxiliary locks and using a key to unlock the factory-supplied locking mechanism, the interior of the station is exposed and sprayed down, to the point of run-off, with the same CDC-approved sanitizing solution. That station is then allowed to rest for several minutes to ensure all pathogenic bacteria and viruses have been neutralized.
Later, after all residual rodenticides have been removed and discarded, the interior of the station is vacuumed of contaminants and wiped clean. Only then is the fully cleansed station re-provisioned with fresh bait, fitted with fresh auxiliary locking devices, secured with the factory-supplied locking mechanism, and placed back on the shelf, ready to be returned to the field.
Late-model versions of the E2M2C™ station include, in addition to rodenticides, a bait panel secured in a void under the rodenticide bait platform. This bait panel is inaccessible to rats and mice but easily accessed by insects. The granular bait coating the panel is labeled for roaches and ants, and is present in sufficient quantities to provide control of targeted insects for the duration of the service interval.
Clean Stations Work Better…
The author discovered, after conducting exhaustive research in the field, that rats and mice prefer fresh, clean baits over those that are contaminated with feces, urine, mold, mildew and moisture. That finding is one that most pest management companies claim to be untrue. Even some of today’s luminaries in the field of modern rodent biology research shake their heads when the author explains his findings in this regard.
One such luminary asserts with confidence that rodent bait stations contaminated with rodent feces and urine are actually preferred by rats and mice over those that are fresh and clean. He is so wedded to this belief that he lectures technicians to carry small bags of rodent pellets with them, to sprinkle in new stations so rats will find them more enticing. He often repeats the time-honored bromide that rats won’t enter bait boxes that are newly introduced in their environment until they have been in place for 7 days or more, despite our findings that — with the E2M2C™ stations — rats go in them and consume their bait provisions within hours after they have been placed.
When the EntomoBiotics Inc. E2M2C™ stations are placed on the perimeters of homes and businesses infested with rats in their walls and attics, it usually takes no longer than 3-7 days for the infestation to be nullified (as evidenced by cessation of rodent noises in the attics and walls). We see this happen time and time again, yet it takes 3 days or more for rats poisoned by rodenticides to succumb to their effects. That fact, alone, provides added proof that rodents enter the E2M2C™ stations soon after they are placed.
Now, some readers will — at this point — shudder at the words “rodenticide.” The author understands, and shares your concerns. Perhaps it is time to dig into the thorny question of rodenticide selection.
There is Also No Shortage of Rodenticide Formulas on Today’s Market…
Lots of different rodenticide baits are presently being marketed in the United States. Definitely too many to list all of them here. Rather than attempt to provide such a listing, a discussion on the various classes of rodenticides that are presently in use follows. This discussion covers the good, the bad, and the ugly facts related to each, but with a warning: A lot of spurious “facts” and “half-truths” about each of these can be found on the Internet.
The National Pesticide Information Center (NPIC), operating under a cooperative agreement between Oregon State University and the U.S. Environmental Protection Agency (U.S. EPA, cooperative agreement # X8-83458501), publishes an informative series of articles on the Internet regarding rodenticides. Within that series is one sheet that summarizes the general classes in broad terms, and is recommended reading for those who wish to obtain a basic understanding of these products. Here, we will cover the subject from another perspective.
Before any rodenticide is approved for use in the EntomoBiotics Inc. E2M2C™ program, the scientific literature is searched for information on its past use, the efficacy of that product in the field, and any safety issues known to exist. If that search indicates that product is suitable for use in E2M2C™ stations, and it appears to possess unique qualities that specially commend it for safe, effective rodent control, it is added to the list of suggested E2M2C™ rodenticides.
Once a given product is put to use it is monitored carefully for durability under a broad range of climatic and environmental conditions, for its acceptability to its target organism, generally the commensal rat and mouse, and for its resistance to contamination by non-target organisms such as ants, slugs, and snails.
lt does not take long to discover problems with specific rodenticides once they are deployed in the field. This is another valuable consequence of the way the E2M2C™ stations are serviced. Since each is returned to the laboratory at each service interval, its contents receive scrutiny under laboratory conditions.
Over time, as laboratory analyses of various bait formulas accumulate, the suitability and efficacy of each bait comes into focus. Bait formulations that melt readily when exposed to moderately high temperatures, that spoil in humid environments, or that attract ants slugs and snails to the rodenticides in the E2M2C™ station are soon removed from the approved list. But, although those criteria are crucial elements in the rodenticide selection process, other considerations are equally important.
As the author points out in another article, rodent control must be carried out in such a way that raptors, the birds of prey that by nature are an essential part of that program, are kept out of harms way. The crucial point here is that the rodenticides used in the E2M2C™ stations must limit, as much as possible, the risk that raptors will suffer from secondary poisoning if they consume rodents poisoned thereby.
Protecting raptors from secondary poisoning is a controversial subject. To some raptor enthusiasts, all rodenticides should be banned because, as they see it, it is impossible to keep raptors from being harmed if they consume a rodent that has been poisoned, regardless of the kind of rodenticide that the rodent consumed. The author understands why that belief persists. It happens, though, that at least one rodenticide — cholecalciferol, also known as vitamin D3 — is both highly lethal to rodents and, according to most authorities, essentially harmless to raptors.
For that reason, the E2M2C™ program emphasizes the use of cholecalciferol over other rodenticides. However, some rodents with apparently finicky palates turn their noses up at cholecalciferol. If a fraction of the rodents visiting the E2M2C™ stations can be expected to fall into that category, at least a fraction of the bait provided in those stations must be formulated with alternative rodenticides that those rodents will consume. If that is not done, that fraction of the rodent population at each site will continue to thrive. Persons familiar with the process of natural selection will recognize the huge red flags emanating from such a process.
All rodenticides, with the sole exception of cholecalciferol, that are on today’s market are capable of posing a risk of secondary poisoning to raptors. Some are so risky that raptors may suffer serious injury after consuming only a few poisoned rodents. Consequently, none in that category are approved for use in the E2M2C™ program. Others are not harmful if only a few rodents poisoned by them are consumed, but become dangerous as the rodenticide — which is not quickly eliminated from the raptor’s body — bioaccumulates in the raptor’s tissues. Here, we find ourselves on the horns of a dilemma.
The E2M2C™ program works to resolve that dilemma through a variety of means. One is to select, as the alternative rodenticide, only those that pose the least risk of secondary poisoning. Another, which is just as important, is to educate every E2M2C™ program client on the imperative of maintaining a strong, consistent rodent control program once the initial rodent infestation has been nullified.
Continuity in Rodent Control: the Key to Stopping Future Home Invasions, as well as the Key to Raptor Protection….
When a home in an established residential subdivision becomes infested with rats, it isn’t unusual for up to sixty rats to be involved in the infestation. Not all of those rats are directly invading the home, however. The invaders are only a subset of the total, and generally constitute the overflow from established rodent nests emanating from habitat in that home’s yard, and from the yards of nearby, neighboring homes. That’s how home infestations work. The home itself generally constitutes a satellite nest, and is not the rodent colony’s primary nesting spot.
That helps explain why the E2M2C™ program works so well, even though — most of the time — the E2M2C™ stations are only placed around the perimeter of the infested home and not inside the attic of the home itself. Don’t try this with ordinary rodent boxes, though, because it probably won’t work. The E2M2C™ stations are specially modified to attract rats to their interiors the moment the rats find them.
Since the invading rodents cannot find food inside the home’s attic, they must leave their attic nests every night to forage outside. In the process they encounter the E2M2C™ stations, enter their interiors right away, consume the bait they find there, and go away to die. As mentioned earlier, it generally takes 3 to 7 days, after placement of the E2M2C™ stations, before the invading rats cease being active inside an infested structure.
The rats that had been invading the home are not the only ones that get into the stations, though. Before long, all the rats in the home’s yard, and a large fraction of those in the neighboring yards, have also entered the stations. The result is — over a period ranging from 30-60 days after the initial placement of the stations — the virtual decimation of the entire rodent colony.
Rat Population Dynamics and Aristotle’s Horror Vacui…
Rat population dynamics play an important role in what happens next. As with all wild animals, individuals in the rat colony constantly reconnoiter the fringes of their established foraging areas to ferret out more space in which to safely roam. Dominant rats from colonies outside those fringe areas make it clear to the reconnoitering interlopers that they are not welcome within their territories. As long as these dominant individuals are active, the existing range for the nearby rat colony remains static. Once those dominant individuals disappear, though, the areas they previously guarded now become available for the taking, and that fact does not go unnoticed.
This is one of the best illustrations of Aristotle’s famous postulate, Horror vacui, roughly translated as “fear of empty space.” The postulate was later restated as “Natura abhorret vacuum” in the 1530s by Francois Rebelais. Aristotle believed that nature contains no vacuums because the denser surrounding material immediately fills any voids that opened up.
Aristotle’s proposition was initially applied to explain abstract physical phenomena dealing with inanimate matter, such as fluid mechanics and the behavior of gasses. Though rightly criticized later by Galileo and a host of scientists who followed, James Clerk Maxwell continued to subscribe to it as late as 1861. Today, though regarded as much less useful in physics than Aristotle imagined, it still helps explain, albeit roughly, the behavior of individuals within animal organizations such as colonies of wild rats.
What it suggests here is that, within any residential neighborhood, the density of rodent activity is in constant flux, and eventually reacts to changes in population densities nearby. As one area becomes less densely populated, the rats in the surrounding areas soon move into that area to fill the void. In the process, an imperfect but somewhat predictable kind of population density continuum is maintained.
Notice the expression used is “population density continuum”, not population density per se. The available rats spread out within the territory available to them, until theirs and the surrounding territories of other rat colonies have achieved a population density common to them all. How dense that population density is at any one time depends on how many rats are present throughout the totality of the territory available. “At any one time” implies that the 4th dimension plays an important role, too. Keep this in mind, as we’ll be returning to its importance before long.
Back to our infested house, once the existing rat colony has been eliminated, all the nesting places they had previously inhabited suddenly go vacant. Rats in neighboring yards take notice of this and, before long, begin expanding beyond their established habitats to those vacant nests. They do this because the individuals composing their existing colonies are by nature constantly seeking ways to expand the territories within which they forage for food. As long as they are not challenged by rats from adjacent colonies, they keep on expanding.
In other words, although most homeowners tend to perceive their homes and yards to be naturally free of rodents (what we earlier described as a mythical belief in a natural, rodent-free status quo) that condition almost never occurs in the real world. Left to itself, without a regular rodent control program in place, all residential yards should expect to undergo a slow but certain increase in rodent populations over time.
In yards with plenty of nesting habitat, and a constant source of food and water, that increase will be rapid. By comparison, yards having a relative lack of those attributes will progress more slowly, but will still see a steady increase in rodent activity over time. Even yards bereft of habitat, food, and water are not left unscathed. At the very least, the rodents in the surrounding yards will still spend time foraging there, even if their soirees are unsuccessful at finding food.
What this means to the savvy humans within any given residential neighborhood is that rodent control is not an event, but a process. That process does not end with the decimation of existing rodent populations. Like freedom, the price of rodent control is eternal vigilance. It must continue, in perpetuity, to constantly nullify newly arriving rodents that are expanding their territories from the home’s surroundings.
The E2M2C™ program is designed to promote that process by keeping costs down and elevating efficacy (at perpetual rodent control) as high as possible. By so doing, it not only offers the best, cost-effective means of keeping rodents under control, it also provides the most efficient way known to protect raptors from the dangers posed by bio-accumulative rodenticides.
Rat Population Dynamics and Raptors…
Raptors, like rats, have established territories. Some — like the northern harrier — are migratory, and their seasonal territories last only until they move on to their other-season haunts. Others — including the red-tailed and white-tailed hawks, and all our Texas owls except for the elf owl (Micrathene whitneyi), that is here in the summer, but migrates south into Mexico during the winter — remain in their established territories throughout the year. In some species, such as the bald eagle, certain individuals migrate seasonally, while others remain within their favorite territories throughout the year.
Because our repertoire of Texas raptors includes such a wild mixture of migratory and non-migrating birds, the protective measures we must employ for them cannot distinguish between the two. In other words, home and business owners must assume the raptors whose territories overlap where they live and work remain there year-round. That imposes the greatest restraint of all on the way we prosecute our rodent control process.
This makes it imperative that the E2M2C™ program use, as its primary rodenticide, a formula that does not cause secondary poisoning in raptors. As mentioned earlier, only one formulation — Vitamin D3, or cholecalciferol — is known to meet this criteria. The choice of the lesser-applied rodenticide comes from a short list of relatively low-risk rodenticides, and is based more on its acceptability to those rodents that shun cholecalciferol than on anything else.
As each of these lesser-applied rodenticides is employed in the E2M2C™ program over time, more and more is learned about their relative acceptability, and that affects rodenticide choice models as we go along. The risk of secondary poisoning of raptors exists with each, unfortunately, so the E2M2C™ program must employ additional measures to protect the raptors that may be plying the skies where the program is in place. At this point, however, the only additional measure open to that program is perpetual rodent control.
Why Not Just Trap the Rodents?
Some will question the assertion made in the previous paragraph, by pointing to the use of various kinds of rodent traps as a suitable alternative. Trapping seems, to the naive observer, to be superior to poisoning for two reasons. First, (except for live traps, discussed later) it offers a way to kill the rodent instantly, rather than making it sick until it dies, and second it appears to only affect the trapped rodent. Neither hypothesis is correct.
The author knows of no rodent trap that guarantees an instant kill. Electrocution traps, a number of which are on the market today, not only cannot guarantee an instant kill, but suffer from other important problems as well. They cannot be used outdoors, so are useless until the rodents gain access to the home’s interior. That makes them of no value as components of a perpetual rodent control program that focuses on keeping the rodent population as low as possible in the yard.
Another problem with electrocution traps is that, as with all other trapping devices, once the rodent has been trapped and killed, all its ectoparasites — mites, ticks, and fleas, each of which is a potential carrier of one or more human disease pathogens — escape its body and migrate to the trap and the immediate surroundings. That means the person handling the trap and the rodent carcass will be exposed to those parasites. With non-electric traps, the risks of such exposure can be mitigated by spraying all surfaces of the trap with a broad-band miticide, pesticide, and bactericide, but treating an electrocution trap that way carries a number of unique risks that argue against the practice.
Ordinary snap traps, whether the time-honored spring activated wire hoop design or the newer plastic jaw variety, are prone to partial trapping of the rodent. This captures a part of the rodent’s body in the trap without killing it. Sometimes the rodent manages to extricate itself by chewing off a limb, but that ultimately results in an agonizing, painful interval before death inevitably ensues. If the rodent cannot extricate itself, it can flop around for hours trying to do so, suffering greatly in the process.
Havahart™ cage traps are thought, by a multitude of naive individuals, to offer the most humane solution of all. The makers of the trap convey that idea by the trap’s brand name, so it is no surprise than many are fooled thereby into using them. The author is acquainted with a number of kind souls who simply cannot kill an animal, even a rat. So they, or someone they hire, disperse a number of rodent-sized Havahart™ cage traps around their yards in a vain attempt to bring their rodent infestation under control. Over time they manage to trap some rats alive and unhurt. When this happens the trapped rodents are taken miles away and “released into the wild.”
Never mind that no matter where these rodents are released, a nearby residence will soon become their new target for infestation. Commensal rodents don’t stay in the wild… they insist on being where humans are, and they will travel as far as necessary to get to where humans are found.
That’s bad enough, but two more issues must also be mentioned. First, once a rodent is trapped in the cage, its cries and noisy efforts to escape catch the attention of all the rodents within earshot. On seeing one of its species captured in a cage trap, the observing rodent will never approach one of those traps again, much less fall for the morsel of food it contains. Placing these traps in a yard or attic is a sure-fire way to create a large population of cage-savvy animals.
The second issue is that, if the trapped rodent is not relocated and released soon after it gets caught in the cage, it suffers greatly while trying to get out. It is rare for animals of all kinds to remain long in a cage trap without causing harm to itself while attempting to escape. This inhumane spectacle is often made worse when the trapper fails to notice that his or her trap contains a live animal; often, the trapped rodent dies in the trap from lack of food and water before it is noticed.
Suffice it to say trapping is not the way to go.
More To Come…
Appendix A: Taxonomy (Family Trees) of the rodents, beginning with Kingdom and proceeding on — through some but not all of the recognized clades — to Phylum, Class, Order, Family, Genus, and Species. Note that on-going advances in DNA sequence analyses, retrotransposon presence or absence data, and the debates such advances engender within the scientific community, are presently muddying the waters of the taxonomical world. That’s frustrating on the surface, but a good thing inasmuch as the confusion that riddles such activities exposes existing caverns of ignorance and eventually breeds advances in knowledge. At the heart of this chaotic atmosphere is the transition taking place between traditional Linnaean taxonomical designations based on anatomical characters, and cladistic nomenclature based on genomic characters. Until this transition is settled by the adoption of a uniform and widely accepted nomenclature any effort to list the taxonomy of a given organism will necessarily include designations that are in dispute. The list that follows reflects that disorder:
Kingdom Animalia (ahn-uh-MAYHL-yuh) — first described in 1758 by the Swedish taxonomist Carolus Linnaeus (23 May 1707 – 10 January 1778), using the Latin word animal = “a living being,” from the Latin word anima = “vital breath”, to refer to multicellular, eukaryotic organisms whose body plans become fixed during development, some of which undergo additional processes of metamorphosis later in their lives; most of which are motile, and thus exhibit spontaneous and independent movements; and all of whom are heterotrophs that feed by ingesting other organisms or their products;
Phylum Chordata (kohr-DAY-tuh) — animals that have, at some point in their life cycle, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail.
Clade Craniata (kray-nee-AH-tuh) — a clade of chordate animals that contains, as living representatives, the Myxini (hagfish), Petromyzontida (including lampreys), and Gnathostomata (jawed vertebrates); craniates are animals with a hard skull, of bone or cartilage, in the phylum Chordata.
Subphylum Vertebrata (vurr-tuh-BRAY-tuh) — chordate animals with backbones and spinal columns;
Infraphylum Gnathostomata (nah-thow-stoh-MAW-tuh) — the jawed vertebrates; derived from the Greek nouns γνάθος (gnathos) = “jaw” + στόμα (stoma) = “mouth”; comprised of some 60,000 species, i.e., 99% of all living vertebrates; living gnathostomes also have teeth, paired appendages, and a horizontal semicircular canal of the inner ear, with other physiological and cellular anatomical characters such as myelin-sheathed neurons, and an adaptive immune system that utilizes V(D)J recombination, rather than genetic recombination in the variable lmyphocyte receptor gene, to create antigen recognition sites; it is presently believed that Gnathostomata evolved from ancestors that already possessed a pair of both pectoral and pelvic fins;
Superclass Tetrapoda (teh-trah-POH-duh) — derived from the ancient Greek expression τετραπόδηs = “four-footed” and comprised of the first four-limbed vertebrates and their descendants, including living and extinct amphibians, birds, mammals, reptiles and some ancient, exclusively aquatic creatures such as the Acanthostega; evolved from the lobe-finned fishes around 390 million years ago in the middle Devonian Period; modern tetrapod groups appeared by the late Devonian, 367.5 million years ago; specific aquatic ancestors of the tetrapods, and the processes leading to land colonization, remain unclear; most present species are terrestrial but the first tetrapods were fully aquatic; most present amphibians are semiaquatic and live the first stage of life as fish-like tadpoles; amniotes evolved about 340 million years ago (crown amniotes 318 mya), and their descendants are believed to have driven most amphibians to extinction; one population of amniotes diverged into lizards, dinosaurs, birds and their relatives, while another diverged into mammals and their extinct relatives; several groups of tetrapods, such as the caecilians, snakes, cetaceans, sirenians, and moas have lost some or all of their limbs; many tetrapods have returned to partially aquatic or fully aquatic lives; the first returns to an aquatic lifestyle may have occurred during the Carboniferous Period; the change from a body plan for breathing and navigating in water to a body plan enabling the animal to move on land is one of the most profound evolutionary changes known;
Clade Amniota (amm-nee-OH-tuh) [Haeckel, 1866] — from Greek ἀμνίον (AMM-nee-awn) = “membrane surrounding the fetus”, and with an earlier meaning of “(the) bowl in which the blood of sacrificed animals was caught”, from ἀμνός (AMM-nos) = “lamb”; a clade of tetrapod vertebrates comprised of reptiles, birds, and mammals that lay eggs on land or retain fertilized eggs within the mother’s body; distinguished from anamniotes (fishes and amphibians) that typically lay eggs in water; include synapsids (mammals along with their extinct kin) and sauropsids (reptiles and birds), as well as their ancestors; amniote embryos are protected by extensive membranes; in eutherian mammals such as humans, these membranes include the amniotic sac that surrounds the fetus; embryonic membranes and the absence of a larval stage distinguish amniotes from tetrapod amphibians; first or “basal” amniotes resembled small lizards and evolved from the amphibian reptiliomorphs about 312 million years ago in the Carboniferous period; their eggs could survive out of the water, allowing amniotes to expand into drier environments; the eggs could also “breathe” and cope with wastes, allowing the eggs and the amniotes themselves to evolve into larger forms;
Clade Synapsida (suh-NAPP-suh-duh) [Osborn, 1903] — the synapsids (from the Greek expression meaning ‘fused arch’), are synonymous with the theropsids (from the Greek expression meaning ‘beast-face’), and include both mammals and every other animal that is more closely related to mammals than to other living amniotes; distinguished from other amniotes by the presence of a temporal fenestra, or opening, low in the skull roof behind each eye having a bony arch beneath each eye that first appeared in the Late Carboniferous period, 312 million years ago, and accounts for the designation; primitive synapsids are often referred to as pelycosaurs or pelycosaur-grade synapsids, while more advanced mammal-like synapsids are referred to as therapsids; the non-mammalian members are described as mammal-like reptiles in classical systematics, and are often called stem mammals or proto-mammals; synapsids evolved from basal amniotes and comprise one of the two major groups of the later amniotes, the other being the sauropsids, which comprises the modern reptiles and birds; synapsids were the largest terrestrial vertebrates in the Permian period, 299 to 251 million years ago, though some of the larger pareiasaurs, appearing at the end of Permian period, matched their size;
Clade Eupelycosauria (yew-puh-lee-koh-SAW-ree-uh) [Kemp, 1982] — originally used to refer to a suborder of ‘pelycosaurs’ (Reisz 1987), but presently used (see Laurin and Reisz 1997) to designate a clade of synapsids that includes most pelycosaurs, as well as all therapsids and mammals; first appeared during the Early Pennsylvanian epoch (e.g., Archaeothyris, and an earlier genus, Protoclepsydrops), and represent a stage in the acquisition of mammal-like characteristics (Kemp 1982), in contrast to their earlier amniote ancestors; defining characteristics separating these animals from the Caseasauria (also pelycosaurs) are based on proportional dimensioning of certain bones of the skull, including a long, narrow supratemporal bone that contrasts with caseasaurs where the width of the supratemporal bone is almost as great as its length, and a frontal bone that widely connects to the upper margin of the orbit (Laurin and Reisz 1997);
Clade Therapsida (thuh-RAPP-suh-duh) [Broom, 1905] — a group of synapsids, including mammals and their ancestors; many traits today seen as unique to mammals had their origin within early therapsids, including having their four limbs extend vertically beneath the body, as opposed to the sprawling posture of other reptiles; earliest fossil attributed to Therapsida is Tetraceratops insignis from the Lower Permian; evolved from pelycosaurs (specifically sphenacodonts) 275 million years ago; replaced the pelycosaurs as the dominant large land animals in the Middle Permian; replaced by the archosauromorphs in the Triassic; the therapsids include the cynodonts, the group that gave rise to mammals in the Late Triassic around 225 million years ago; of non-mammalian therapsids, only cynodonts and dicynodonts survived the Triassic–Jurassic extinction event; the last of the non-mammalian therapsids, the tritylodontid cynodonts, became extinct in the Early Cretaceous, approximately 100 million years ago;
Clade Neotherapsida (nee-oh-thuh-RAPP-suh-duh) [Hopson, 1999] — a clade of therapsids, that includes anomodonts and the more derived theriodonts, which include mammals;
Clade Cynodontia (sinn-oh-DON-tee-uh) [Owen, 1861] — therapsids with “dog teeth” that first appeared in the Late Permian, some 260 million years ago; includes modern mammals, including humans, as well as their extinct ancestors and close relatives; non-mammalian cynodonts spread throughout southern Gondwana and are represented by fossils from South America, Africa, India, and Antarctica; in northern continents, fossils have been found in eastern North America as well as in Belgium and northwestern France; one of the most diverse groups of therapsids;
Clade Mammaliamorpha (muh-may-lee-uh-MOHR-fuh) — the clade originating with the last common ancestor of Tritylodontidae and the crown group mammals, and as such a wider group than mammaliaformes, such that it includes some families that trait-based taxonomy does not include in Mammalia, in particular Tritylodontidae and Brasilodontidae;
Clade Mammaliaformes (muh-may-lee-uh-FOR-mees) [Rowe, 1988] — a clade containing the crown group mammals and their closest extinct relatives; the group, which radiated from earlier probainognathian cynodonts, is defined as the clade originating from the most recent common ancestor of Morganucodonta and the crown group mammals; the latter is the clade originating with the most recent common ancestor of extant Monotremata, Marsupialia, and Placentalia; besides Morganucodonta and the crown group mammals, it includes Docodonta and Hadrocodium as well as the Triassic Tikitherium, the earliest known member of the group; Mammaliaformes is a term of phylogenetic nomenclature; by contrast, the assignment of organisms to Mammalia has traditionally been founded on traits and, on this basis, Mammalia is slightly more inclusive than Mammaliaformes; trait-based taxonomy generally includes Adelobasileus and Sinoconodon in Mammalia, though they fall outside the Mammaliaformes definition;
Class Mammalia (muh-MAIL-yuh) [Linn. 1758] — from the Latin noun mamma = “breast”, a clade of endothermic amniotes distinguished from reptiles and birds by the possession of a neocortex region in the brain, hair, three middle ear bones and mammary glands; includes the largest animals on the planet, the great whales, as well as some of the most intelligent, such as elephants, primates and cetaceans; basic body type is a terrestrial quadruped, but some mammals are adapted for life at sea, in the air, in trees, underground or on two legs; the largest group of mammals have a placenta, which enables the feeding of the fetus during gestation; mammals range in size from the 30–40 mm (1.2–1.6 in) bumblebee bat to the 30-meter (98 ft) blue whale; except for the five species of monotreme (egg-laying mammals), all modern mammals give birth to live young; most mammals, including the six most species-rich orders, belong to the placental group; the three largest orders in number of species are Rodentia: mice, rats, porcupines, beavers, capybaras and other gnawing mammals; Chiroptera: bats; and Soricomorpha: shrews, moles and solenodons; the next three biggest orders, depending on the biological classification scheme used, are the Primates including the great apes and monkeys; the Cetartiodactyla including whales and even-toed ungulates; and the Carnivora which includes cats, dogs, weasels, bears and seals;
Magnorder Boreoeutheria (boh-ree-oh-yew-THEE-ree-uh) — from the Greek noun βόρειο = “north” + the Greek adjective ευ = “good” + the Greek noun θεριό = “beast”; a magnorder, which the International Code of Zoological Nomenclature (ICZN) uses to designate a clade of unusually important significance, of placental mammals comprised of the sister taxa Laurasiatheria (most hoofed mammals, most pawed carnivores, and several other groups) and Euarchontoglires (Supraprimates); this magnorder is now well supported by DNA sequence analyses, as well as retrotransposon presence or absence data; the earliest known fossils belonging to this magnorder date to about 65 million years ago, shortly after the K-Pg extinction event, though molecular data suggests they may have originated earlier, during the Cretaceous period; with the exception of rhinoceroses and cetaceans, male members of the clade share the distinction of external testicles.
Superorder Euarchontoglires (yew-ARR-chawn-toh-GLY-rees), also referred to as Supraprimates. This forms both a clade and a superorder of mammals belonging to the five groupings known as rodents, lagomorphs, treeshrews, colugos, and primates.
Grandorder Glires (GLY-rees) from a Latin word meaning dormice. This grouping includes rodents and lagomorphs (i.e., the rabbits, hares, and pikas). Though still in dispute, recent morphological analyses give credence to treatment of Glires as a monophyletic group.
Order Rodentia (roh-DEN-chee-uh) from the Latin word Rodere, meaning “to gnaw”. Rodents are mammals having one pair of incisors, in the upper and lower jaws, that continue growing throughout the life of the rodent.
Appendix B: Listing of all the Known Arboreal, Terrestrial, and Burrowing Rodents found in Central Texas.
The nearly 2,000 species of rodents that are presently recognized worldwide comprise about 40% of all living mammals. 68 rodent species are known to be found in Texas, and 24 of these are found in Central Texas, all fully capable of invading yards, landscapes, and man-made structures.
Rodents are distinguished from other mammals by the kinds and arrangements of their teeth: all rodents have a single pair of upper, and a single pair of lower incisors that are separated, from several pairs of chewing teeth, by a large gap (diastema). The chewing teeth of typical mice consist only of molars, while squirrels and their allies, jumping mice, and cavylike rodents have both molars and premolars. Rodent incisors grow continuously from birth to death, and have chisel-like cutting edges:
Pocket gophers (Geomyidae)
- Llano pocket gopher (Geomys texensis): subterranean; common in west-central part of Central Texas; small, dark brown or sandy brown on back, paler sides, white underparts; prefers deep sandy loam, gravel, or sand in Texas Hill Country; breeds in spring and early summer.
Pocket mice & kangaroo rats (Heteromyidae)
- Hispid pocket mouse (Chaetodipus hispidus): terrestrial, throughout Central Texas; head and body 3.75 inches; large and colorful, with brown back, grizzled with orange and black; a broad orange lateral line on sides; white belly, broad orange ring around eye, bicolor tail is short and not tufted; breeds year-round; prefers grassy areas in plains and deserts, usually on sandy soils.
- Merriam’s pocket mouse (Perognathus merriami): terrestrial, throughout Central Texas; head and body 2.25 in, tail 1.75 in.; breeds Mar-Dec; found on sand, gravel, and hard-packed soils.
- Silky pocket mouse (Perognathus flavus): terrestrial, throughout Central Texas; head and body 2.25 in.; tail 1.75 in., shorter than other pocket mice; very small; grizzled orange-brown back, with pale orange lateral line, and white belly; sifts through sand for seeds, climbs stalks to harvest green seeds; breeds Mar-Oct; prefers sandy soils, rocky areas, and clays.
Mice & rats (Muridae)
- Black Rat (Rattus rattus): arboreal, terrestrial, and opportunistically subterranean throughout Central Texas; head and body 5-7 in., tail 3-4 in.; scraggly black to light brown fur with lighter undersides; nocturnal, congregating around warehouses, residential buildings, and similar human settlements; prefer in urban settings to live in palm and pines; nests are ball-shaped and are made of shredded sticks, leaves, vegetation, and cloth; will build nests in abundant leaf litter and thick ground cover and under some circumstances will burrow into the ground; generalist omnivores, adapt to food supplies available locally; excellent vectors for disease transmission due to an ability to carry bacteria and viruses in their blood streams; particularly known to carry Streptococcus pneumoniae, Corynebecterium kutsheri, Bacillus piliformis, Pasteurella pneumotropica, and Streptobacillus moniliformis; preyed on by owls, cats, foxes, and coyotes.
- Brown Rat (Rattus norvegicus): subterranean, terrestrial, and arboreal throughout Central Texas: head and body 8-10 in., tail 7-10 in.; brown or dark gray back with light gray underparts; nocturnal, excellent swimmer and burrower, often excavating extensive burrow systems; true omnivores, though cereals form substantial part of diet; breed throughout the year, females able to produce 5 litters annually; gestation period is 21 days, pups become sexually mature in five weeks, permitting populations to grow by a factor of 10 in 15 weeks; live in large, hierarchical groups in burrows or subsurface places such as sewers and cellars; generally begin new burrows adjacent to an object or structure, as this provides a roof for the set ion of the burrow nearest to the ground’s surface; burrows develop to include multiple levels of tunnels as well as a secondary entrance; burrows are used to escape perceived threats; carry a number of pathogens and parasites.
- Deer Mouse (Peromyscus maniculatus): terrestrial, arboreal, and subterranean, throughout Central Texas; head and body 3.5 in., tail 2.25 in.; so closely related to the white-footed mouse (Peromyscus leucopus) that the two are best distinguished via RBC agglutination tests or karyotype techniques, though, physically, the deer mouse is distinguishable by its long, multicolored tail; 66 subspecies are recognized, all are tiny and plentiful throughout their range; nocturnal, foraging by night, spending day in trees or burrows, the latter having nests of plant matter; reproduce throughout the year, esp. Mar-Oct, var. based on food availability; preyed on by snakes, owls, skunks, foxes, and domestic cats.
- Eastern woodrat (Neotoma floridana): terrestrial, semi-arboreal, and subterranean pack rat, on eastern edge of Central Texas; head and body 9 in., tail 6.25 in., moderately haired; back gray brown, dark brown, or sandy brown; sides washed with buff; belly grayish white or cream white; ears large; eats leaves, fruit, berries, fungi, nuts, and seeds; in east Texas uses underground burrows; breeds year round; common, widespread, and able to thrive in a wide variety of habitats.
- Fulvous harvest mouse (Reithrodontomys fulvescens): arboreal and terrestrial, on northern, eastern, and southern edges of Central Texas; head and body 2.75 in., with long tail; back rusty brown peppered with black, sides orange, belly white or buff; breeds in spring and fall; constructs baseball sized nests of shredded plant material in vegetation.
- Hispid cotton rat (Sigmodon hispidus): terrestrial and subterranean throughout Texas; head and body 6 in., tail 4 in.; upper parts grizzled dark brown and buff, belly grayish white; mainly crepuscular but active day or night; eats grass and other plants, insects, and fungi; makes nests in thick grass clumps or short underground burrows.
- House mouse (Mus musculus): terrestrial, throughout Central Texas; head and body 3-3.9 in., tail 2-3.9 in.; fur light to dark brown; adults are good jumpers, climbers, and swimmers, are crepuscular or nocturnal, sleep 12 or more hours a day, and nest in cryptic places near food sources; naturally omnivorous, but preferentially feeds on plant matter; known to be capable of transmitting a few human diseases, including Lymphocytic choriomeningitis, but such infections are not commonly reported and, when diagnosed, are generally mild; mice often contaminate food and damage food packaging; mice tend not to be as infested with fleas as rats, and thus are not effective vectors of plague.
- Northern pygmy mouse (Baiomys taylori): terrestrial and subterranean, throughout Central Texas; head and body 2.5 in., tail 1.75 in.; dark gray-brown back, gray sides, grayish white belly; small eyes, medium ears, tail short and nearly naked; mainly nocturnal but sometimes diurnal; eats seeds, fruit, green vegetation; nest is ball-shaped with one or two openings, and is situated under logs, in vegetation, and in small burrows.
- Plains harvest mouse (Reithrodontomys montanus): terrestrial, throughout Central Texas; head and body 2.7 in., tail 2.25 in.; feeds on weed flowers and seeds, and on grasshoppers and other invertebrates; nest is ball shaped constructed on or just above the ground; breeds year round; prefers open countryside with short grasses.
- Southern plains woodrat (Neotoma micropus): terrestrial, in western half of Central Texas; head and body 8.5 in., tail 6 in.; large, with back and sides steely gray or blue-gray, white belly; eats cactus leaves and fruit, mesquite beans, acorns, and plant matter; makes a house under prickly pear cactus, with 2-5 entrances, and likely uses the house for life.
- Texas mouse (Peromyscus attwateri): terrestrial and semi-arboreal throughout Central Texas; 3.75 in. head and body, 4 in. tail; eats seeds, other plant materials, and insects.
- White-ankled mouse (Peromyscus pectoralis): terrestrial, throughout Central Texas; head and body 3.75 in., tail 3.75 in.; gray-brown upper parts, brown sides with narrow orange lateral line, white belly; often found on rock ledges and in leaf litter; eats juniper berries, acorns, hackberries, seeds, and invertebrates; breeds year round.
- White-footed mouse (Peromyscus leucopus): terrestrial, semi-subterranean, and semi-arboreal, throughout central Texas; head and body 3.5 in., tail 3 in.; dark brown upper back, sides orange-brown, white belly; eats seeds, nuts, fruit, invertebrates, and vegetable matter; makes ball-shaped nests in logs, standing trees, abandoned burrows, bird nests, and inside man-made structures; breeds mainly in spring.
- Woodland vole (Microtus pinetorum); subterranean, throughout Central Texas; head and body 4 in., tail 0.75 in.; reddish brown back, orange-brown sides, gray belly; eyes and ears small; eats roots throughout the year, grass stems in summer, fruit and seeds in the fall, bark in winter; breeds year round; favors sandy soil.
- Black-tailed prairie dog (Cynomys ludovicianus): subterranean; along the western edge of Central Texas; though capable of invading yards and landscapes, it is unlikely to do so.
- Eastern gray squirrel (Sciurus carolinensis): arboreal and terrestrial; eastern half of Central Texas; uppermost parts gray with yellow-brown cast on upper back and head; white or pale orange eye-ring; ears gray to rusty brown, sometimes white with slight tuft in winter; white belly; mainly arboreal but spends much time on ground; nest made of twigs, leaves, and plant material, in hollow trees or inside hollow trees; each squirrel uses more than one nest; breeds twice a year in Jan-Feb and June-July; favors hardwood forests.
- Fox squirrel (Sciurus niger): arboreal and terrestrial; throughout Central Texas; variable in color but most commonly grizzled yellow-brown above, with pale orange to rusty brown belly, cheeks, eye-ring and feet, and tail edged in orange-brown; larger than eastern gray squirrel where range overlaps; travels and rests in trees, but feeds extensively on ground; eats nuts, acorns, seeds, fungi, and fruit; makes leaf nests on branches, in hollow trees, or in voids of man-made structures; mates Jan-Feb and May-June; prefers open stands of deciduous and evergreen woodlands, shunning woods with dense undergrowth or closed canopies.
- Mexican ground squirrel (Ictidomys mexicanus): subterranean and terrestrial; throughout Central Texas; feeds on mesquite leaves and beans, grass and herb seeds, insects, carrion, and small vertebrates. It makes burrows that have multiple entrances, and willingly uses the burrows of pocket gophers. It prefers areas with sandy soils.
- Rock squirrel (Otospermophilus variegates): arboreal, terrestrial; throughout Central Texas; in Texas most commonly found with blackish head and shoulders, dark brown or cream forelegs, but can be entirely black with a pale eye-ring and yellowish belly; mostly seen on the ground but capable of climbing well and sometimes nests in trees; eats fruit, seeds, plant matter, roots, cacti, and invertebrates; prefers rocky canyons, cliffs, and hillsides in arid areas.
- Thirteen-lined ground squirrel (Ictidomys tridecemlineatus): subterranean and terrestrial; along the eastern edge of Central Texas; is the “gopher” most people notice along roadsides, on lawns, and on golf courses. It eats seeds of grasses and herbs, but will also consume small insects and vertebrates. Though they will form colonies when conditions permit, adults are not social and defend only the areas around their nest burrows. Deeper nest burrows are built near shallow escape burrows. They prefer short grass meadows and prairies, and avoid wet, low-lying areas.
- Lee, Michael J., et al. 2018. Effects of Culling on Leptospira interrogans Carriage by Rats. Emerging Infectious Diseases, Vol. 24, No. 2, February 2018.
- Murray, Maureen Heather, et al. 2018. Public Complaints Reflect Rat Relative Abundance across Diverse Urban Neighborhoods. Front. Ecol. Evol. doi: 10.3389/fevo.2018.00189.
- Parsons, Michael H., et al. 2017. Trends in urban rat ecology: a framework to define the prevailing knowledge gaps and incentives for academia, pest management professionals (PMPs), and public health agencies to participate. Journal of Urban Ecology, 2017, 1-8.
- Parsons, Michael H., et al. 2018. Temporal and Space-Use Changes by Rats in Response to Predation by Feral cats in an Urban Ecosystem. Front. Ecol. Evol. 27 September 2018.
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