Rare Species Guide

  Basis for Listing

The range of the plains hog-nosed snake is confined to central North America, ranging from southern Canada through the central United States to northern Mexico. In Minnesota, it has been found at widely scattered localities in a limited number of counties. The plains hog-nosed snake was listed as a special concern species in Minnesota in 1984 primarily due to loss of habitat. However, collection for the pet trade is also a concern.

  Description

The plains hog-nosed snake is a medium sized, stout-bodied snake. Adults range from 38-63.5 cm (15-25 in.) long, with the record size being 100.6 cm (39.6 in.) long (Conant and Collins 1998). The dorsal ground color is light yellowish-tan to grayish-olive, or even a rich brown. There are a series of dark oval middorsal blotches with smaller ones along the sides. The ventral surface is white to yellowish with masses of dark pigment, sometimes with yellow or orange mixed in. The head is marked with long dark blotches, and the snout is sharply upturned and used for digging. The scales are keeled and the anal plate is divided. This species resembles its close relative, the eastern hog-nosed snake (Heterodon platirhinos), but the eastern hog-nosed snake has a less upturned snout, and the underside of its tail is lighter than the rest of the belly (Oldfield and Moriarty 1994). A hog-nosed snake will flatten its head like a cobra when approached and it may hiss and strike or feign death when harassed.

  Habitat

The plains hog-nosed snake is a habitat specialist, preferring open, sparsely vegetated habitats on well-drained soils. Dry prairie habitats are preferred, but it may also inhabit oak savanna habitats. Pocket gopher burrows are also frequently utilized.

  Biology / Life History

Plains hog-nosed snakes overwinter below the frost-line in mammal tunnels or self-dug burrows, and emerge from hibernation early in the spring (Oldfield and Moriarty 1994). Breeding usually takes place in mid-April through May (Oldfield and Moriarty 1994). Females lay 2-24 eggs (Ernst and Barbour 1989) in late May to early July, and young emerge after 50-65 days (Oldfield and Moriarty 1994). The young are 17-19 cm (6.7-7.5 in.) long at hatching (Ernst and Barbour 1989).

The plains hog-nosed snake's home range is relatively small. The longest movement recorded for this species was that of a female that traveled 1.6 km (1 mi.) in about 10 months (Ernst and Barbour 1989).

The plains hog-nosed snake consumes toads, frogs, salamanders, lizards, small snakes, and small rodents (Summarized in Wright and Wright 1957) and it subdues its prey with mildly toxic saliva. Eggs are also eaten, including those of turtles, lizards, snakes, and ground nesting birds. The main predators of plains hog-nosed snakes are foxes, coyotes (Canis latrans), raccoons (Procyon lotor), hawks, and American crows (Corvus brachyrhynchos) (Oldfield and Moriarty 1994). This snake has three main anti-predation defenses. Because it is generally docile, its first line of defense is to attempt to escape down a hole or bury itself in dirt. Its second is to make itself look bigger by flattening its neck and head. It may also raise its head, hiss loudly and strike with a closed mouth. If this does not deter the harasser, the snake may try its third line of defense and feign death. It does this by writhing around, rolling onto its back, and remaining motionless with its mouth open and tongue hanging out. It may also regurgitate a recent meal or let feces ooze out of its vent. The plains hog-nosed snake will occasionally lift its head to see if the threat has passed. Once the threat is gone, the snake will right itself and move away.

Although the plains hog-nosed snake has mildly toxic saliva, it poses no significant danger to humans. A bite from this species may cause some swelling and discoloration at the site of the bite.

  Conservation / Management

The major threat to the plains hog-nosed snake is habitat loss caused primarily by agriculture and urban sprawl. Snake populations that occur near urban areas are threatened with extirpation when roads and developments fragment their open, grassland habitat. In residential areas, people who encounter plains hog-nosed snakes may be frightened by their cobra-like defense posture, and kill them. Although popular as pets, most hog-nosed snakes kept as pets today are captive bred. Wild-caught individuals are not as adaptable to captivity.

The plains hog-nosed snake is often difficult to locate because of its habit of lying at the entrance of a burrow and quickly retreating inside when disturbed. Where they are known to occur, grassland management practices that reduce encroachment of brush and trees can enhance habitat for this snake species. General prescribed burning guidelines have been developed for amphibians and reptiles in the Midwest, although land managers conducting burns in areas with known rare reptile or amphibian species or high concentrations of reptiles and/or amphibians may wish to contact their Regional Nongame Wildlife Specialist for input on burn planning, including timing of burns, so as to minimize impacts on these species. Conservation efforts that connect areas of open grassland across the landscape may also enhance the viability of known populations of plains hog-nosed snakes.

  Conservation Efforts in Minnesota

While habitat loss is a significant threat to plains hog-nosed snake populations in Minnesota, protection and management of grasslands and savannas helps enhance remaining habitats.

Surveys conducted by the Minnesota Biological Survey (MBS) and Nongame Wildlife Program program have targeted snakes within the plains hog-nosed range. However, these surveys have resulted in relatively few additional observations for this species. In hopes of collecting additional records of this secretive species, the MBS distributed fliers to the public requesting reports of any plains hog-nosed snake sightings. Unfortunately, very little response was generated from the fliers.

  References and Additional Information

Conant, R., and J. T. Collins. 1998. A field guide to reptiles and amphibians of eastern and central North America. Third edition. Houghton Mifflin Company, New York, New York. 616 pp.

Ernst, C. H., and R. W. Barbour. 1989. Snakes of eastern North America. George Mason University Press, Fairfax, Virginia. 282 pp.

Oldfield, B., and J. J. Moriarty. 1994. Amphibians and reptiles native to Minnesota. University of Minnesota Press, Minneapolis, Minnesota. 237 pp.

Wright, A. H., and A. A. Wright. 1957. Handbook of snakes of the United States and Canada. 2 Volumes. Comstock Publishing Associates, Ithaca, New York. 1105 pp.