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Western Hognose Snake - Heterodon nasicus PDF Print E-mail
 A Field Guide to Amphibians and Reptiles of Iowa
  

 

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See the Minnesota HerpNet Site for more about the Western Hognose Snake  

Synonyms: Plains Hog-nosed Snake.

Status

ENDANGERED. It is illegal to kill or collect this species by law in Iowa. Western hognose snakes need a special habitat to survive in Iowa. Unfortunately, most of that habitat is now gone. We really need records from the western part of Iowa! Please report sightings to us. 

Western Hognose Snake, Heterodon nasicus
Western Hognose Snake, Heterodon nasicus, from Louisa County, Iowa
 

Description

This is a medium sized Iowa snake ranging from 15 to 39 inches in length. It is a very heavy-bodied serpent. It is considered nonvenomous. The 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. These blotches are brown, but not black. The belly is shiny jet black with small yellow or whitish squares, often many squares clustered together.

Western Hognose Snake, Heterodon nasicus, playing dead
Western Hognose Snake, Heterodon basicus, playing dead, from Louisa County, Iowa
 

The anal plate is usually lighter colored than the belly. The underside of the tail is black. The rostral scale is enlarged; protruding outward and upward like a hogs snout. The snout comes to a point and there is a heavy keel along the top. Western hognose snakes have smaller scales around their snouts. Other snake species, such as rat snakes, have no smaller scale separation; the prefrontals and internasals are all touching on the snout. The body scales are keeled and the anal plate is divided.

Subspecies

The plains hognose snake, Heterodon nasicus nasicus, occurs in Iowa. Some elevate the plains subspecies to full species status.

Range

In Iowa, the plains hognose snake has a very spotty distribution due mostly to a preference for a particular habitat and the result of habitat fragmentation and destruction. The sand prairies in which it lives are now very rare in Iowa. Populations may be found in the Mississippi Alluvial Plain and a small area of northern Iowa. Past records indicate loss of populations in Iowa (Christiansen, 1998). If a specimen is found, contact us.

County Records for the Western Hognose Snake in Iowa
County Records for the Western Hognose Snake in Iowa
 

Habitat

This snake has a strong preference for sandy or gravelly situations. Western hognose snakes 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. This is how most populations are lost. They, like some other Iowa herps (LeClere, 1998), cannot adapt to changes that alter their strictly sandy habitats. See also range and habitat sections for the bullsnake and the box turtle.

Habits

The western hognose snake is best known for is its method of protection. When confronted, it may remain still to blend in with its surroundings or it may hide its head under its coils. If discovered, the hognose will spread its jaws and neck like a cobra while puffing up its body. This is one of the few Iowa snakes that actually hiss with great vigor; only the bullsnake rivals it. The hognose will strike, but with a closed mouth! This behavior causes it to be called blow snake, spreading adder, hissing adder, or puff adder by local people. 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, the serpent remains limp and lifeless. It may bleed from the mouth and cloaca and expel musk or fecal matter or even 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. platirhinos. Only one thing gives the act away: if it is righted, it will immediately roll onto 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.

Heterodon nasicus also may use its burrowing capabilities to escape. Using its upturned snout, it can burrow out of sight amazingly fast. The western hognose snake is diurnal except in very hot weather when they may aestivate. They are most active in the morning and evening. They may not use artificial cover as often as other snakes, as they sometimes use mammal burrows and can also construct very temporary burrows themselves. On an 80 F. day in May in Hennepin County, MN, I found a specimen in a burrow under a piece of tin. It was upside down and I suspect that it was using a variation of thermoregulation.

Western hognose snakes overwinter from October to March or April in mammal burrows. 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. The young are very similar in appearance to the adults.

Food

These snakes are voracious feeders and consume any smaller animals they find. Frogs, toads, lizards, small snakes, reptile eggs, ground-nesting bird eggs, rodents, and small birds. Carrion is also consumed and young snakes may apparently eat insects. I found an adult male in Louisa County on 5 July that had consumed two turtle eggs. Other authors have reported western hognose snakes feeding upon turtle eggs as well (Barten 1980, Iverson 1990, Kolbe 1999, Platt 1969). Western hognose snakes are not constrictors and simply swallow prey alive.

Hognose snakes have enlarged rear maxillary teeth and some believe they may use this feature to deflate toads which may puff themselves up with air to unswallowable proportions. The teeth are more likely used to assist in the introduction of saliva into prey, however. 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 (H. nasicus) and southern hognose snakes (H. simus) contain parotid glands. This appears irrelevant, however, as many cases of envenomation have been caused by the eastern hognose (H. platirhinos) which lacks the parotid glands. Due to studies, 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. platirhinos so please refer to the account on Heterodon platirhinos, the eastern hognose snake.

 
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