—This article by Jerry Cates et al., first published in March 2007, was last revised on 24 April 2016. © Bugsinthenews Vol. 08:03.
The eastern hog-nosed snake (Heterodon platirhinos) is a medium sized snake that comes in a variety of colors and markings. It has a stout body, a broad head and thick neck. When the snake is threatened, the skin of the neck and head spreads laterally, similar to that of a cobra. The eastern hog-nosed snake, however, is a harmless serpent (albeit with a mildly toxic saliva, and a pair of backward-facing fangs deep in its throat) that feeds on toads, frogs, rodents, and similar prey.
Synonyms: puff adder, spreading adder.
Coloration and markings: variable, ranging from unmarked, vaguely marked, or marked with highly contrasting marks consisting of blotches, squares, or mixtures of both; the bodies and markings are variably colored from drab brown or black to bright yellow, red, green orange, or cream. The belly, visible when the snake plays dead, is generally unmarked, and lighter in color than the body; the underside of the tail is lighter than the belly, a feature that distinguishes this species from the western hog-nosed snake (Heterodon gloydi), the underside of whose tail is dark in color.
- Snake Repellents: How and how well do they work?
- Snake Exclusion–How to “Snake-proof” your yard and home.
- Definition: A reasonably snake-free environment.
CASE 040510: SHIRLEY, KEMPNER, TX:
This snake was found inside of a BBQ place in Kempner on 4-5-10. It was lying on top of the expansion joint board of the concrete floor. It will flatten its head and strike at you. Total length was about 8 inches. What kind of snake is it and what area is it most likely to be found?????
I informed Shirley that this was a juvenile eastern hog-nosed snake, in the genus Heterodon, and the species platirhinos. The generic name Heterodon is from the Greek ετερο-, hetero “unlike, different” + δόντια -dontia “teeth”, thus “having different teeth, teeth that are not all the same kind”, a reference to the fact that these opisthoglyphous serpents have rear-facing fangs deep in their throats.
Opisthoglyphous fangs assist the snake in swallowing prey, making it difficult for the prey to escape once snagged by the fangs. They also assist in puncturing the bodies of puffed-up toads, deflating air sacs that are used by such prey to prevent them from being ingested. Despite having such fangs, and possessing a mildly toxic saliva (a kind of numbing anesthetic that probably assists in subduing prey, thus making it easier to swallow them), these snakes are not considered dangerous to man or his large pets. Of course, if you have a pet toad, mouse, or rat, all bets are off.
Here, in this discussion about these snakes, it might be wise to interject a bit of sage advice concerning human interactions with these serpents: while mature, sober adults of average or higher intelligence are unlikely to stick their fingers down a snake’s throat, inebriated or otherwise mentally impaired adults, and young children, may be more unpredictable in the placement of their hands and fingers. Thus, it is unwise to allow such individuals to play with one of these serpents except under adult supervision. If a finger is inserted deeply into the snake’s throat, it may become impaled on one of the rear-facing fangs. If this occurs, extricating the appendage will be complicated, and the experience will not end well either for the person attached to the finger or for the snake (which is now also attached to said finger); furthermore, the mildly toxic saliva of the snake can produce local swelling and pain, and–in some unusual circumstances–even worse complications.
One of the first things one notices when encountering this snake in the wild (anywhere an undomesticated specimen happens to be is, by definition, “the wild”, so my use of the expression is more a reference to the snake’s undomesticated state than to the setting) is its flared head, neck, and body.
According to one authority (Greene, 1997, p. 113), the way a snake displays its head can make it look larger than it really is, and can also imply a willingness to bite. Green points out that the character of the head display differs, depending on the way the snake typically meets an aggressor (i.e., an animal, including man, whose intent is generally to destroy the snake):
In the case of the North American hog-nosed snakes in the genus Heterodon, as well as for Old World cobras, such encounters generally involve the snake being on the ground, looking upward at its enemy. And, says Dr. Greene, such an orientation tends to favor a defense that involves flattening the snake’s anterior, dorso-ventrally.
That is, the flattening of the forward portion of the body, the head and neck, is highly exaggerated in the horizontal plane. The dorsum is flattened, or maximized, and the ventrum is also, while the lateral surfaces of the body are minimilized.
Greene goes on to say that arboreal species like birdsnakes and twigsnakes (none of which are native to the U.S. or Canada) usually face their adversaries laterally, and that orientation favors a defense wherein they inflate their necks.
It is interesting that, although Shirley’s specimen does not do so, the Eastern Hog-nosed Snake often does both. It is common for these snakes to display prominent swellings of the neck (or at least the cheeks) just posterior to the head in addition to flattening the head and body. However, the vertical swelling Green referred to does not occur.
Notice the transverse dark bar that crosses over the head, splitting into two parallel bars across the crown; the distal ends of this bar extend to the posterior extent of the mouth-line. Knowing this enables us to determine how far the mouth-line extends back from the nose without actually seeing the mouth-line itself.
Not all snake species are easy to sex just by looking at their bodies. For example, none of the rat snakes in the genus Elaphe, and none of the rattlesnakes in the genus Crotalus, are easily sexed from outward appearances alone. However, the sex of some snake species, including the Eastern Hog-nosed Snake, can usually be determined just by looking at the posterior third of the snake’s body.
Notice that the posterior body of Shirly’s specimen tapers abruptly, at a certain point, from a relatively stout girth to a much narrower girth, where the snake’s tail commences.
The hemipenes of the male of the species are normally withdrawn into that portion of the snake’s body posterior to the vent, where the tail begins. For that reason, the external anatomy of the male Eastern Hog-nosed Snake displays a gentle taper from the vent to the tip of the tail.
The female, however, being without a similar structure in this portion of the body, has a comparatively diminutive tail. The markings of the tail differ from those of the main body, in that, while those of the body consist of spinal blotches separated by narrow, pale interstices, and darker lateral spots consistent with the pale spinal interstices, those of the tail appear as simple dark bands (actually half-rings, as they do not continue with the same intensity, if at all, across the caudal underside) separated by pale, narrow bands.
It should be pointed out that these markings, while common to many specimens, are unusually variable in this species. Coloration, too, varies greatly.
The most common color, according to John E. Werler and James R. Dixon, in their 2000 book “Texas Snakes” (p. 139-40), is yellowish brown, yet individuals displaying shades of yellow, orange, red, brown, olive, gray, or black, are not unusual.
Sometimes these colorations appear to be geographically dominant, suggesting that genetic pools that favor some coloration and marking combinations over the other are concentrated in those locales. For reasons described more fully in the case histories that follow, below, geographic dominance of specific colors and markings tends result from the influence of at least two factors: (1) the dominant background colors and markings in the typical environment, and (2) the behavior of common predators in that locale. In some cases, these influences lead to subdued colors and markings that are either absent, vaguely defined, or irregular, while in others they lead to startling contrasts of bright and dark markings arranged in sharply distinct patterns.
Shirly’s specimen lies between these two extremes, being of a moderately brown coloration with regular, well-defined markings.
CASE 041710 CHARLOTTE S., BOERNE, TEXAS:
I live in Boerne, Texas, and my neighbor removed this snake from my back yard yesterday. We are pretty sure it is an eastern hog-nosed snake but wanted to see if you could confirm that. It did play dead when inside the container. My neighbor took it down the street to let it out The snake’s underside was bright orange.
After I wrote back confirming her identification, she added the following question:
I wonder if you have any suggestions for keeping snakes out of a yard. We had a snake last summer which we think was also an eastern hog-nosed snake, and it shed its skin under our grill. I have four young children, and I worry about them coming across a snake in the yard. I know the hog-nose is not venomous but I still worry about a snakebite for the little ones. I have had recommendations for Snake A-Way repellent, but I wondered if that really works. Someone else also mentioned that snakes don’t cross lava rocks, but the hog-nose that shed its skin did so in a pile of lava rocks around our grill.
Besides directing Charlotte to articles on snake repellents, snake exclusion, and what it means to have a relatively snake-free environment, my reply emphasized that eastern hog-nosed snakes are particularly fond of toads and frogs (especially toads), so creating an environment that has few or none of those animals is an essential part of keeping these snakes out of our yards.
Toads and frogs spend the nighttime hours hunting down insects, but hole up in cool, damp retreats that they burrow into the ground, usually under rocks or other natural or man-made structures. These animals require a pond or pool with a shallow area in which to breed, and a hunting habitat of dense vegetation that they can hide and forage in. If these are present in a yard, the likelihood that toads and frogs will be plentiful is high. That means, too, that the snakes that are attracted to such animals will be plentiful as well.
Charlotte’s specimen is relatively dark in color, with mottled markings, which would help camouflage the snake in the deep forests that grow on rich, alluvial soils.
CASE 042110 SHADY GROVE, TEXAS
From time to time I receive e-mails with attached images and no accompanying text. Most of the time, these are sent by individuals who have just snapped a photo using their cell phone’s camera. One such e-mail arrived on 21 April 2010 from a location in east Texas.
The attached photo, shown at left, is of a female eastern hog-nosed snake (note the curlique tail, which is a dead giveaway that this specimen is of the fairer sex) with a pinkish brown background coloration and muted, chevron-like markings.
A return message was sent giving a short description of the snake, that since it’s harmless and keeps the toad population down, it’s a “good” snake. The photographer, being a woman of few words, didn’t reply, so I got her on the line and inquired where the photo was taken. It turned out to be in the little farming community of Shady Grove, Texas.
Now, that doesn’t say a lot, because a bunch of places, scattered all over Texas, are named Shady Grove.
This particular farming community, however, is in the Piney Woods of east Texas, in Upshur County. Settled in the 1850’s, and once with its own high school (opened 1889), and post office, now it’s little more than a wide place on Farm Road 1002, some twelve miles west of the city of Gilmer (Upshur County seat, with a 2000 pop. of 4,799, home of the east Texas Yamboree and of the state-championship-winning football team, the Gilmer Buckeyes), and about the same distance north of the town of Big Sandy (2000 pop. of 1,288, famous for its involvement in the Worldwide Church of God, hosting the Big Sandy campus of WWCG’s Ambassador College — which today is the International ALERT Academy — and the Big Sandy Wildcats High School football team, winner of three Texas Class B state championships).
CASE 042510 NW AUSTIN, TX — CORINNA R.
We are VERY new to Texas, and we’ve had a hard time identifying this snake.
We encountered it on our hike this morning in Steiner Ranch, in Northwest Austin.
Would you mind letting us know what kind it is?
This is — of course — an eastern hog-nosed snake in medium gray, with no markings that we can discern.
Steiner ranch is off of FM 620, in Travis County, just north and east of Lake Travis.
The geography there is karst limestone hill country, and the coloration of this specimen blends in with the limestone rocks that cover most of the surface area here.
That probably explains — at least to some extent — why we find a lot of eastern hog-nosed snakes in this area with gray backgrounds and no markings.
It’s easy to miss them if they aren’t moving. And a snake that isn’t noticed tends to live another day. Camouflage is a form of mimicry, in which the organism mimics the background environment it spends much of its time traveling over or through. Like Batesian mimicry (where non-venomous snakes and palatable butterflies, to give just two examples, mimic venomous snakes and unpalatable or toxic butterflies) the organism’s prevalent coloration is driven by external conditions that favor the longevity of specimens that have certain color patterns and place statistical limits on the propagation of others.
In another article I discuss how the eastern hog-nosed snakes in the Sam Houston National Forest mimic the pygmy rattlesnakes in that locale.
They don’t “try” to mimic them, but because there are so many pygmy rattlesnakes in the area, and animals tend not to molest them, being mistaken for one bodes well for living a long life.
Notice that Corinna’s specimen has a pronounced nose scale, but that it is not upturned at all.
Many eastern hog-nosed snakes have nose scales that are not as distinguished from the surrounding scales as this one, but none turn up at the tip.
Another species, the western hog-nosed snake (Heterodon gloydi), does have an upturned nose scale, and that is one of the distinguishing marks used to tell them apart.
CASE 061510 TOM SINCLAIR, SAM HOUSTON NATIONAL FOREST:
In another article the Batesian mimicry — by certain eastern hog-nosed snakes in the Sam Houston National Forest — of the pygmy rattlesnakes found in that locale is discussed in some detail.
I won’t duplicate that material here, but you may wish to click on that link and read it over. In an earlier case (041510, Corinna R., NW Austin), we noticed how that eastern hog-nosed snake has a coloration that allows it to blend in with its limestone surroundings.
That was not a coincidence, for reasons explained in that text. Imagine how Tom’s specimen would look in the karst hill-country, stretched out on a slab of limestone that had been bleached to a uniform gray by the hot Texas sun. It would stick out like a sore thumb.
That might not affect its ability to hunt toads, but it would wreak havoc with its ability to avoid being preyed on by wild animals and humans, the latter being famous for having a tendency to kill every snake that is seen.
In the Sam Houston National Forest, though, things are different. There the wild animals stay away from snakes with these colors and markings, because they look so much like those of the pygmy rattlesnake (Sistrurus miliarius streckeri). And humans are constrained from killing any animals, including venomous snakes and their mimics, in our national forests.
CASE 033007: LORRAINE EDEN, COLLEGE STATION, TEXAS:
Lorraine wrote the following on 30 March 2007:
I opened the skimmer to the pool this morning, and found this fellow curled up inside it. Do you have any idea what kind of snake it is?
This young lady (she is quite young, of course, though she has a PhD, is a published author, and serves as a highly respected professor at a major Texas university) has sent me a number of excellent wildlife photos in the past. In 2006, for example, I posted her photos of a spiny-backed orb weaver (Gasteracantha cancriformis). Now she has found a snake in her pool skimmer and, with characteristic nonchalance, wonders what kind it might be.
Obviously, Lorraine has dealt with lots of different kinds of snakes in her life. Just negotiating the thickets of academia, jumping through the hoops one must thread to obtain a doctorate in her chosen field, would itself do that. Then, as an educator, I’d guess she sometimes finds the rigors of professor-student interactions similar to, say, hiking an Amazonian rain forest in the rainy season… But Lorraine is much more than a university professor. She’s recognized worldwide as an authority on the political economy of multinational enterprises, and transfer pricing. She’s currently researching such arcane topics as strategic transfer pricing, foreign direct investment in tax havens and corrupt economies, and much more. She’s written several significant books, too, like Taxing Multinationals (1998); Governance, Multinationals and Growth (2005); Multinationals in North America (1994); Multinationals in the Global Political Economy (1993); Retrospectives on Public Finance (1991); and Multinationals and Transfer Pricing (1985).
From the first e-mail I received from Lorraine, her calm demeanor intrigued me. It suggested that she has faced, and surmounted, a host of difficult situations in the past, and developed excellent coping skills as a result. Like opening up a pool skimmer, coming face-to-face with a snake, and — instead of jumping up and screaming like a little girl — calmly replacing the lid, getting her camera, and shooting a few photos so she can learn more about the serpent’s identity.
Gotta respect somebody with cool nerves like that. Now, knowing more about her life and work, I think I understand.
The eastern hog-nosed snake she encountered was small. Assuming the skimmer opening was about eight inches in diameter, the snake’s body was less than an inch wide at mid-body; that would make it an adolescent, perhaps one or two years old at most. It flared its neck defensively, as such snakes are wont to do, but it had nothing to worry about. Lorraine the nature-lover would never harm it. And now, knowing as she does that it feeds on the toads around her pool, keeping their numbers in check so she and her pets don’t have to worry about stepping on a 6-pound toad one of these days, she has one more reason to be grateful for the diversity of wildlife in her yard.
References to Scientific Articles, Papers and Books:
- Cates, J. 2012. Index to North American Snake Families, Genre, & Species.
- Conant, R., and J. T. Collins, 1998. Reptiles and Amphibians — Eastern/Central North America, Third Ed. Peterson Field Guides. Houghton Mifflin Co.
- Greene, H. W., 1997. Snakes: the Evolution of Mystery in Nature. University of California Press.
- Tennant, A.,1998. A Field Guide to Texas Snakes, Second Ed. Gulf Publishing.
- Werler, J. E., and J. R. Dixon. 2000. Texas Snakes. University of Texas Press.
- Wickler, W. 1968. Mimicry in plants and animals. New York: McGraw-Hill.
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