Common Name: Hognose Snake, Puff adder, Spread-head moccasin, Blowing viper, Possum snake, Hissing adder, Puff head – The distinctive upturned and pointed snout is somewhat imaginatively comparable to that of hogs.
Scientific Name: Heterodon platirhinos – A heterodont is any animal that has teeth that are differentiated into incisors, canines and molars, literally “different teeth.” It refers in this case to two enlarged teeth that are in the posterior section of the upper jaw for this genus. The species name is a combination of the Greek platys meaning flat or broad and rhin meaning nose, again referring to the flattened nose of the snake.
Potpourri: The reason for the mildly pejorative and descriptively inaccurate name hognose – hogs have rounded snouts – is that it is the singular feature that can be consistently and readily discerned; hognose snakes are highly variable in both hue and pattern. The background color can be yellow, tan, brown, reddish, or gray with a maculated overlay that consists of dark brown-to-black square or diamond shaped patches with more rounded blots along the sides and back; the entire tessellated scale pattern is sometimes limned in bright orange. There are even hognose snakes with an all-black melanistic presentation; one of the earlier scientific names (1854) was Heterodon niger (Latin for black). The widely divergent and random variations in the color of the hognose snake suggest that there is no evolutionary factor involved in palette selection. Animals generally employ crypsis, the use of muted earth-tone colors blended with the environment, to either conceal them from predators or to afford an enhanced secrecy against prey. Striping is also employed to confuse predators, and to some extent this applies here. Bright colors more commonly imply aposematism – providing a vivid sign to predators to stay away from what is likely a toxic meal. Since the hognose snake can have either muted or bright colors, it must be concluded that skin patterns are not important in the ability to capture prey nor are they important in their ability to evade predators; it is not a genetic selection criterion as there is no preference in survival.
The surprisingly complex behaviors of the hognose snake when threatened, on the other hand, are characteristic of all color variants; it is therefore indisputable that these behaviors are survival factors. The hognose snake might well be called the harlequin snake, as its theatrical performance when threatened instantiates the quick-witted and foppish harlequin that was a stock caricature of the commedia dell’arte. Act one is the masquerade; with head erect, the neck is flattened and an ominous hiss emanates like a cobra – the alternative common names puff adder and spread-head moccasin are descriptions of the verisimilitude. Depending on the intruder’s fight or flight reaction to the feigned aggression, a striking lunge may follow for added effect. And if that doesn’t work, act two, the death scene, is employed. According to Linzey and Clifford in Snakes of Virginia “If poked or kicked the snake will writhe in apparent agony with mouth open and tongue dragging in the dust. Feigned death soon overtakes the poor creature and it lies limply on its back.” The alternative common name possum snake is apropos as opossums employ a similar tactic. Snakes of more Thespian affect may take this even further by defecating and writhing in the offal to smear their lifeless body with repulsive slime; they have even been known to regurgitate their last meal – perhaps nothing could be more scatological than a partially digested toad. That this is a determined and elaborately staged ruse is without doubt. If a redoubtable naturalist researcher turns the snake right-side up, it will immediately return to the supine. Once the danger is past, act three is to resume normal locomotion, exeunt stage right. The extravagant masquerade undoubtedly deters many of the normal snake predators such as raccoons, foxes, opossums, and, for unfortunately phobic reasons, humans. Hawk, owl and king snake predations, which occur at a lightning strike rate, are unaffected by the snake mime.
The upturned snout that gives the hognose snake its name is not unique to the species H. platirhinos that is indigenous to North America; there are also snakes known as hognose due to their similar physiognomy in Africa and South America. As the various hognose snakes are in different genera, the characteristic shape is an example of convergent evolution, the development of similar attributes in adaptation to similar environmental factors. The upturned and widened anterior adaptation provides a superior digging tool for burrowing into the arenaceous soils that are its primary habitat. Enhanced digging enables the hognose snake to excavate its own burrow (one of the few snakes with this propensity) and, more importantly, enhances its ability to capture its primary anuran prey – burrowing toads.
The hognose snake does not need to employ crypsis to catch prey – it is literally a consummate amphibian predator with a penchant for toads. Their ability to dig into toad burrows obviates the need to hide in ambush. However, there is much more to the toad preference than gustatory satisfaction. Most snakes subsist on a primary diet of rodents and small birds, avoiding toads entirely for a very good reason. Toads produce bufotoxins that are harmful to humans and deadly to dogs and many snakes. Not only are hogback snakes immune to bufotoxin but they are armed with two toad-piercing teeth that are covered with toad-killing saliva. The generic name Heterodon was chosen to provide the hognose snake a taxonomic distinction in having “different teeth.” The two specialized grooved teeth at the rear of the mouth, opisthoglyphous in the lexicon of zoology, are ideally positioned to hold a struggling toad long enough for the poison to act. Hognose snake saliva is hemotoxic; it kills the toad’s red blood cells – erythrocytes. There is some conjecture as to whether the teeth also act to puncture the toad’s lungs to promote deflation necessary for ingestion. This is a moot point, as a poisoned dead toad will not breathe for long. The veracity of their dietary preference was validated unequivocally by a research project conducted in 1939. Three herpetologists captured, killed and dissected 10 hognose snakes in George Washington National Forest to reveal that their last meal was 40 percent toads, 30 percent frogs, 11 percent salamanders (81 percent amphibians) with the balance of 19 percent consisting of small rodents. There is no doubt that the hognose snake is a toad nemesis nonpareil.
Aside from the Shakespearean drama of predator confrontation and the stomach turning notion of toad consumption, the hognose snake is but one of the nearly 2,000 colubrid species with their attendant characteristics. The family Colubridae comprises about two thirds of all snakes that are generally characterized as not venomous – which leads to something of a paradox. Hognose snakes produce a hemotoxin that is deadly to toads and mildly venomous to humans but are still considered not poisonous. The reason is that the teeth are not fangs and the poison is not injected as a matter of purpose as is the case with the pit vipers like the timber rattlesnake and the copperhead. Hognose snakes reproduce annually, laying about twenty eggs, grow continuously, molting about once a year, and live to the ripe old age of six. The hognose snake is simply a non-venomous, toad-eating snake that puts on a good show.