— This article by Jerry Cates, first published on 23 March 2010, was last revised on 23 October 2013. © Bugsinthenews Vol. 11:03(21).
The most easily obtained snake repellent on the U.S. market today uses a mixture of naphthalene crystals and sulfur granules. That product, which relies on the interference of its ingredients with the snake’s Jacobson’s organ, has been tested by a number of authorities, including at least one university — under laboratory conditions — and found to repel a wide number of snake species, including many rattlesnakes, in particular when these snakes are performing Jacobson’s organ/olfactory-mediated searches (that is, when they are following, or searching for, scent trails) for prey and/or mates at ground level.
FOOD FOR THOUGHT: Snakes, both venomous and non-venomous, often take up residence in the attics, basements, walls, and other portions of residential and commercial structures. Most home or business owners are not equipped to properly perform a serpent removal and exclusion project at their homes or businesses. You may believe you are an exception to this rule, and it may be true. If, however, you don’t have the time or interest needed to (1) study all the technical issues involved, (2) tackle all the mechanical habitat modifications, (3) obtain and properly use the protective gear needed to avoid injury from the snake and its associated disease-causing organisms, (4) inspect for, find, and then seal all the ingress/egress ports in your home’s or business’s exterior, (5) clean up, disinfect, and remove the contaminants left behind by the snake, and (6) do all this within a reasonable time, you are no exception. In that case, what you need is a wildlife specialist with expertise in reptile biology, removal, disinfecting and control. To find a qualified wildlife specialist in your local area (anywhere in North America), call Jerry RIGHT NOW at 512-331-1111.
Regardless of how well a repellent works in the lab, laboratory conditions and those encountered in the real world are quite different. That is particularly true for snakes and the complicated habitats within which they move, live, and forage.
Besides being mildly toxic, and being notorious for lacing your clothing with a strong, objectionable odor that lingers until the clothing is laundered, no naphthalene/sulfur based product has been found to reliably repel snakes that are attracted to, and that consume, decaying flesh. The latter include copperheads, cottonmouths, some rattlesnakes, and most of the non-venomous rat and water snakes. This seems to result from the fact that the chemicals expressed at tissue decay and putrefaction are similar to the repellent’s constituent ingredients.
We first learned about this serious performance gap many years ago, after several applications of the napthalene/sulfur granules failed to keep snakes away from yards and structures under our control. Accordingly, we began an investigation into the various alternative chemical repellents and adjunctive mechanical measures at hand. The list of such agents and methodologies, from all outward indications, is quite long for both groups (chemical and mechanical), and so — apparently — is the list of those conducting similar investigations.
Inasmuch as the failings of today’s presently marketed snake repellents are common knowledge, a multitude of manufacturers have sprung up to market a host of “new” and “novel” chemical repellents. Unfortunately, many of those materials are of questionable utility. Others are clearly of no value whatever. Furthermore, not one works against all species of snakes all the time, even when used exactly as the label dictates. Yet, granular and liquid snake repellents that are touted as capable of always repelling all species of snakes are presently being marketed on the Internet under a number of brands.
Few or none of these various materials have been subjected to rigorous, scientific testing — in the laboratory or in the real world — to determine if, and under what circumstances, they actually work. Most chemical repellents claim to disrupt the function of the snake’s Jacobson’s organs, much as naphthalene/sulfur granules do, but without the disagreeable odor and toxicity of the latter. Presumably, this accrues from the fact that the strong, natural fragrances associated with them bear no resemblance to decaying flesh. But do these repellents work as advertised? Only a series of well-designed scientific tests, in the lab and in the wild, will tell for certain. Such testing is so expensive and time consuming, however, that it exceeds the budgets of most repellent manufacturers.
Beyond that question, however, lies another: just how crucial is the Jacobson’s organ as a determinant of where a snake will or won’t go?
Many snakes prey on birds and their eggs, and on arboreal rodents such as squirrels. These snakes, including but not limited to the colubrid rat snakes, often travel considerable distances aerially, from tree to tree, without ever touching the ground where repellents have been applied. Though some repellents can be applied to trees, repeated wholesale arboreal treatments are not practicable. Thus, a yard that is blessed with numerous trees having interconnected crowns may be visited regularly by arboreal serpents regardless of the presence of terrestrially-applied repellents underneath.
Likewise, nearly all snakes spend part of their lives underground, and some are, by nature, entirely fossorial (living most if not all of their lives under the soil). Some of our most venomous serpents prefer to hunt for prey under the ground rather than above, when given a choice. Subterranean dens and tunnels are often intricately connected in a labyrinthine maze of immense proportions, and such passageways may abound beneath many yards without any overt indication of their existence. Some of their small entry/exit ports at ground level are often hidden from view of even the most careful investigator.
The number of cryptic entry/exit holes available to snakes in a yard increases considerably if the landscape — or the home situated on that lot — is blessed with natural or man-made structures such as rock outcroppings, drystack rock fences, concrete patios and foundations with unsealed peripheries, large dog houses or storage sheds with wooden floors sitting on the ground, or wooden decks closely situated over expanses of ground that cannot be visually surveyed. Within such yards, applications of snake repellent in the traditional manner–around the perimeters of the yard, in the landscaping,. and around outsides of structures, may fail to protect that property, regardless of the kind of repellent that is utilized.
Some snakes, notable among them the coachwhips, racers, and whipsnakes, almost never use their Jacobson’s organs to hunt for prey. They rely instead on large eyes that offer excellent visual acuity, along with an ability to raise their heads high above the ground as they travel about scanning the terrain in all directions for insects, lizards, and rodents. It is unreasonable to expect such snakes to be deterred by strong-smelling granules or sprays, especially when they are visually tracking prey.
It is fair to assert, then, that none of the snake repellents on the market can be trusted to repel all species of snakes all of the time. It is therefore unwise to rely on snake repellents alone — regardless of the repellent’s chemistry — as a means of eliminating snake sightings within a specific area. On the other hand, by using snake exclusion techniques, which rely on mechanical habitat modifications, in conjunction with a well-planned and executed PestAvoidance program that reduces ophidian habitat and prey in yards and structures, tends to sharply reduce the risk of snake incursions without the use of any kind of snake repellent at all, often to the point that the human residents of such areas only rarely, if ever, see a snake.
Even in such locales, however, an unpleasant surprise may pop up from time to time, in quite unexpected places. Several times a year reports come in of snakes inside homes, most often in bathrooms. Such snakes easily enter these homes via the sewer system, usually but not always via a commode. Sewers, being similar in many respects to the natural subterranean hibernacula snakes have used as shelter for millennia, provide excellent habitat for most serpents. Plain water, in the P-trap of a sink or commode, is not an effective barrier to such snakes, especially when they are chasing prey. It is surprising, then, that reports of snakes being found in bathrooms are not more numerous. This has led many to believe that finding an effective remedy that utterly prevents snake incursions from household sewers presents challenges that are practically insurmountable.
In conclusion, the general efficacy of a particular snake repellent cannot be assured without considerable evaluation and testing that takes place over a period of several years. Besides that, even a highly effective snake repellent cannot prevent aerial incursions from arboreal snakes in heavily forested yards whose trees have interconnected crowns. The same caveat applies to yards underlain with subterranean passageways. And, last, even the most thorough snake exclusion program will be defeated, from time to time, by serpents th This at enter the home from a sewer connection.
is likely to be more information than many, especially those who are deathly afraid of any snake they see, wish to hear, let alone digest. The fact is that snakes are — to at least some extent — inevitable, and those who wish to reduce the risk of seeing such animals in their yards or homes are well advised not to look on snake repellents as stand-alone solutions. A comprehensive program of snake exclusion. however, often produces highly satisfactory results.
Related Links on BugsInTheNews:
- North American Snake Markings & Coloration Guide.
- Ophidian Dentition — Snake Teeth & Fangs — Morphology & Specialization
- Snake Anatomy, Physiology, and Taxonomy.
- Snake Exclusion — How to Snake-proof your Yard and Home.
- Snake Repellents — How, and How Well, do They Work?
- Snakebite First Aid.
- Snakes, Rodents, & Droughts.
- What is Meant by “A Reasonably Snake-Free Environment”?
- Southern Copperhead (Agkistrodon contortrix contortrix); Dana T., Allen, Texas–05.02.09
- Broad-Banded Copperhead (Agkistrodon contortrix laticinctus): Steve B., Round Rock TX–2 July 2009
- Cottonmouths & Copperheads in Travis and Harris Counties, Texas — June to August, 2010
- Western Cottonmouth (Agkistrodon piscivorus leucostoma, Troost 1836); Tammy D., Santa Fe, TX — 28 Aug 2011
- Western Cottonmouth (Agkistrodon piscivorus leucostoma, Troost 1836) juvenile snakebite; Margaret Archer, Manvel, TX — 5 Sep 2011
- Western Diamond-backed Rattlesnake (Crotalus atrox, Baird & Girard, 1853), Cedar Creek, TX — 22 Oct 2010
References to Scientific Articles, Books, and Papers:
- Arikan, Hüseyin et al. 2008. Electrophoretic characterisation of the venom samples obtained from various Anatolian snakes(Serpentes: Colubridae, Viperidae, Elapidae). N.W. J. Zool. Vol. 4, No. 1, pp.16-28.
- Birchard, Geoffrey F., et al., 1984. Foetal-Maternal Blood Respiratory Properties of an Ovoviviparous Snake; the Cottonmouth, Agkistrodon piscivorus. J. exp. Biol. 108, 247-25
- Chao, Betty H., et al. 1989. Agkistrodon piscivorus piscivorus platelet aggregation inhibitor: A potent inhibitor of platelet activation. Proc. Natl. Acad. Sci. USA Vol. 86, pp. 8050-8054
- Chippaux, J. P., et al. 1991. Snake Venom Variability: Methods of study, results, and Interpretation. Toxicon Vol. 29, No. I I , pp. 1279-1303.
- Conant, Roger, and Joseph T. Collins, 1998. Reptiles and Amphibians — Eastern/Central North America, Third Ed. Peterson Field Guides. Houghton Mifflin Co.
- Cundall, David. 2009. Viper Fangs: Functional Limitations of Extreme Teeth. Physiological and Biochemical Zoology 82(1):63–79.
- Deufel, Alexandra, and David Cundall. 2004.Functional plasticity of the venom delivery system in snakes with a focus on the poststrike prey release behavior. Zoologischer Anzeiger 245 (2006) 249–267
- Grachevca, Elena, et al., 2010. Molecular Basis for Infrared Detection by Snakes. Nature, 15 April 2010.
- Greene, Harry W., 1997. Snakes: the Evolution of Mystery in Nature. University of California Press.
- Schulz, Klaus-Dieter, 1996. A Monograph of the Colubrid Snakes of the Genus Elaphe Fitzinger. Koeltz Scientific Books.
- Tennant, Alan,1998. A Field Guide to Texas Snakes, Second Ed. Gulf Publishing.
- Weinstein, Scott A., et al. 1994.Reptile Venom Glands — Form, Function, and Future. Handbook of Venoms and Toxins of Reptiles. CRC Press.
- Werler, John E., and James R. Dixon, 2000. Texas Snakes. University of Texas Press.
- World Health Organization. 2002. Management of Snakebite and Research. WHO SEA-RES-2.
- Zaidan, Frederick III, 2002. Variation in cottonmouth (Agkistrodon piscivorus leucostoma) resting metabolic rates. Comparative Biochemistry and Physiology Part A 134 (2003) 511–523
- Zamudio, Kelly R., et al., 2000. Fang tip spread, puncture distance, and suction for snake bite. Toxicon 38 (2000) 723 – 728
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