Western Hognose Snake
Heterodon nasicus

by Jeff LeClere

Status

Due to habitat preference and collection pressures, this snake is listed as a species of Special Concern in Minnesota.

Description

This is a medium sized Minnesota snake ranging from 15 to 39 inches in length. It is a very heavy-bodied serpent. It is considered nonvenomous. Its ground color is usually some shade of brown with darker brown blotches down the back. There are two alternating rows of smaller dark spots along the sides. There is a large longitudinal blotch on both sides of the neck. The belly is shiny jet black with small yellow or whitish squares, often many squares clustered together. The rostral scale is enlarged; protruding outward and upward like a hog's snout. The snout comes to a point and there is a heavy keel along the top. The scales are keeled and the anal plate is divided.

Subspecies

There are three subspecies of H. nasicus. One of these, the plains hognose snake, Heterodon nasicus nasicus, occurs in Minnesota. It intergrades with the dusty hognose snake, Heterodon nasicus gloydi, in southern U.S. where their ranges meet. The dusty hognoses are distinguished by the softer "dusted" appearance and they have fewer body blotches (less than 32 in males and less than 37 in females). Plains hognoses' body blotches number more than 35 in males and more than 40 in females. The Mexican hognose snake, Heterdon nasicus kennerlyi, often the most colorful subspecies, differs in having 2-6 small scales between the internasals and prefrontals instead of nine like the other two subspecies. Other snake species, such as rat snakes have no smaller scale separation; the prefrontals and internasals are all touching.

Range

In Minnesota, the plains hognose snake has a very spotty distribution due mostly to a preference for a particular habitat and habitat fragmentation/destruction. Western and central Minnesota have the most concentrated populations, but many small, isolated populations can be found where suitable habitat is left.

Habitat

This snake has a strong preference for sandy or gravelly situations. They like sand prairies,very open portions of prairies, or sand dunes with very little cover. Habitat destruction or other environmental changes may push this snake out of its natural habitat and force it to live in more wooded biomes; many simply will not adjust to these changes.

Habits

This snake is best known for is its method of protection. It is clumsy and slow compared to many other Minnesota snake species. When it is confronted, it may remain still to blend in with its surroundings or it may hide its head under its coils. If discovered, it will spread its jaws and neck to the extent of a cobra while puffing up its body. This is one of the few Minnesota snakes that actually hiss with great vigor; only the bullsnake rivals it. It will strike, but with a closed mouth! If this front fails and persecution persists, it will twist and turn as though in pain and then roll over on its back and play dead! With a wide open mouth and tongue hanging out, nothing can persuade it to move. Even if it is picked up it remains limp and lifeless. It may bleed from the mouth and cloaca and expel musk or fecal matter or regurgitate. It closes off the opening to the esophagus and salivates. This is to prevent the swallowing of dirt and is readily observed in H. platyrhinos. Only one thing gives it away; if it is righted, it will immediately roll on to its back again. If left alone the snake will crawl away and resume its activities. The eastern hognose is quite a bit more eccentric with its act than the western hognose. H. nasicus also may use its burrowing capabilities to escape. Using its upturned snout it can burrow out of sight amazingly fast.

This snake is diurnal except in very hot weather when it may aestivate. They are most active in the morning and evening. They may not use cover as often as other snakes, as they sometimes use mammal burrows and can also construct burrows themselves. On an 80 F. day in May in Hennepin County, MN, I found a H. nasicus in a burrow under a piece of tin. It was upsidedown and I suspect that it was using a variation of thermoregulation. They breed in the spring and, perhaps more commonly than thought before, again in the fall. They are oviparous laying anywhere from 2 to 30 or more eggs in a clutch with the most common number of eggs being somewhere in the middle of that range. The young Hognoses are 5-8 inches when they hatch in August or September. They hibernate from September to March or April in mammal burrows.

Food

These snakes are voracious feeders and consume any smaller animals they find. Frogs, toads, lizards, small snakes, reptile and ground-nesting bird eggs, rodents, and small birds. Carrion is also consumed and young snakes may eat insects.

Hognose snakes are opisthoglyphous (having fangs at the back of the mouth) and they use this feature to "deflate" toads which may puff themselves up with air to unswallowable proportions. I mentioned earlier these snakes were non venomous, but there is some evidence that they may be mildly venomous. Although hognoses have fangs, they apparently have no ducts or grooves through which venom could be administered. They also have no venom glands but two species, the western and southern hognose snakes, H. simus, contain partoid glands. This appears irrelevant, however, as many cases of envenomation have been caused by the eastern hognose which lacks the partoid glands. It is thought that the venom is hemotoxic. It is not known whether it is an actual venom that is produced or reactions due to saliva or bacteria. These snakes can hardly be induced to bite, even in the wild, and therefore cases are rare. There are more cases involving H. platyrhinos so please refer to the account on Heterodon platyrhinos.