Western hognose snake
July 31, 2009 28 Comments
Another herp interlude…
During my visit to Salt Plains National Wildlife Refuge in northwestern Oklahoma this past June, tiger beetles were not the only wildlife subjects I encountered. Near the edge of one of the alkaline flats along Sandpiper Trail was this hognose snake. This is the second hognose snake that I’ve encountered in as many years, the first being a member of a rare, disjunct population of the dusty hognose snake (Heterodon nasicus gloydi) in one of southeastern Missouri’s critically imperiled sand prairie habitats. There are two species of hognose snake in Oklahoma – eastern (H. platirhinos) and western (H. nasicus). I presume this individual to be the western due to its strongly upturned rostral (snout), which is only moderately upturned in the eastern species, and black-checkered ventral coloration. Surprisingly, in checking the Salt Plains reptile species list for confirmation on its identity, I noted that no confirmed sightings of either the eastern or western hognose snake have been recorded at the refuge. I have since done my good deed to reptile science by submitting this and another photograph I took of the individual to the refuge biologist. Ted MacRae – entomologist and discoverer of new reptile records! Western hognose snakes are further classified into three subspecies, two of which – dusty and nominotypical – occur in Oklahoma (the third occurs in Mexico). However, the distinctions between the two U.S. subspecies are subtle¹ and not apparent in this photograph, preventing further classification.
¹ Some authors consider the dusty and western hognose snakes to be separate species, while others have regarded their differences too subtle to warrant even subspecific distinction.
Hognose snakes are famous for their well-choreographed sequence of defensive displays. Their first act is to rear up cobra-like and strike out with their mouth open while hissing (unfortunately, neither of the hognoses I’ve encountered entertained me in this manner). If the threat continues, they then turn over and writh violently in mock agony before finally rolling over on their backs and playing dead (thanatosis). Last year’s hognose snake didn’t do this either, insisting instead on continually trying to burrow into the loose sand. As can be seen from the photograph above, however, playing dead is exactly what this individual did. With the mouth agape and the tongue protruding, it’s a convincing display of lifelessness. Amusingly though, whenever the snake was righted it immediately turned over on its back again – not such a good imitation of being dead! Presumably the snakes predators are as bad at noticing that detail as are the snakes themselves. As I continued to pester this individual, trying to get him to stick out his tongue further for a better photograph, he eventually started ejecting blood from the lacrymal glands and emitting musk from the cloaca – what better to emphasize a death display than blood and an offensive smell!
Western hognose snakes are classified as a species of ”least concern” on the IUCN Red List of Threatened Species and aren’t listed as a species of concern on the Oklahoma Natural Heritage Inventory database. Nevertheless, as with many other reptiles and amphibians, populations are declining throughout much of their former range. This is likely due to the combined effects of urbanization, reduction of habitat, predation by feral dogs and cats, and overcollection for sale to the pet trade.
Copyright © Ted C. MacRae 2009