Montana Field Guide

This is a heavy-bodied snake with a broad neck and dark blotches on the back extending from the back of the head onto the tail. There is much black pigmentation on the underside of the body, with contrasting patches of white, yellow, and orange, and the anal scale is divided. The snout is upturned, with an enlarged rostral scale that is spade-like and keeled. The dorsal scales are also keeled. There are enlarged ungrooved teeth near the rear of the upper jaws. The maximum total length is about 90 centimeters, but most individuals are less than 65 centimeters. Hatchlings are similar to adults in appearance and about 17 to 20 centimeters total length. Eggs are smooth and elongate (usually 26 to 38 millimeters x 14 to 23 millimeters in length and breadth).

The presence of an upturned snout that is spade-like and keeled, in combination with keeled dorsal scales, a dark-patterned belly, a divided anal scale, and the absence of tail rattles and facial pit, distinguishes the western hognose snake from all other snakes native to Montana. The color pattern is described as similar to both the gopher snake and the western rattlesnake, but neither of these, nor any other snake in Montana, has an upturned nose like the western hognose snake.

No information is available for Montana. Marked individuals in Kansas were usually recovered during the same year within a few hundred meters of their previous capture site; occasionally individuals moved a kilometer or more between years (Platt 1969, Hammerson 1999).

Little specific information for the state is available. They have been reported in areas of sagebrush-grassland habitat (Dood 1980) and near pine savannah in grassland underlain by sandy soil (Reichel 1995, Hendricks 1999).

In other locations, their apparent preference for arid areas, farmlands, and floodplains, particularly those with gravelly or sandy soil, has been noted. They occupy burrows or dig into soil, and less often are found under rocks or debris, during periods of inactivity (Baxter and Stone 1985, Hammerson 1999, Stebbins 2003).

Little is known about the food habits of this carnivorous species in Montana. In northeastern Montana, the diet consisted of 42% amphibians, 31% small mammals, and 27% reptiles (Flath 1969).

Based upon research in other areas where the species is found, the western hognose snake is considered a specialist predator on toads, but other main items in the diet include lizards and reptile eggs, and to a lesser extent frogs, salamanders, snakes, birds, and mammals (Baxter and Stone 1985, Hammerson 1999); young eat proportionally more lizards and lizard eggs than do larger snakes, which sometimes eat birds and other snakes, items not eaten by the young (Platt 1969). It commonly uses its spade-like nose to dig up buried prey detected by odor, such as painted turtle and yellow mud turtle eggs (Iverson 1990), and may use toxic saliva to subdue active prey.

Little information is available specific to Montana. However, western hognose snakes are known to be diurnal. Their active period extends primarily from late April to mid-October in Colorado (Hammerson 1999). The active period in Montana is poorly documented, with records from mid-May to the end of September, and mostly from early June to early August (Mosimann and Rabb 1952, Reichel 1995, Hendricks and Reichel 1998, Hendricks 1999). Population density was estimated at about 4 to 6 per hectares in Kansas pasture, about half of this was in an ungrazed area (Platt 1969).

The few confirmed predators include hawks (Buteo spp.), American Crows, and coyotes (Platt 1969, Hammerson 1999). Predators of the western hognose snake in Montana have not been reported. When disturbed, western hognose snakes may flatten their heads and vigorously strike and hiss. If these methods fail to deter a threat, individuals may exhibit death-feigning behavior that includes writhing, rolling over on the back, letting the tongue hang from the mouth, and remaining limp. If turned right side up, individuals will immediately roll over on their backs again (Hammerson 1999). Montana individuals also show this death-feigning behavior (Mosimann and Rabb 1952).

There is almost no information specific to Montana. A female collected in Toole County on July 20, 1950 contained seven eggs ready for laying (Mosimann and Rabb 1952).

Information from other locations indicate that western hognose snakes lay clutches of 3 to 23 eggs in shallow burrows or nests a few inches below the surface (Platt 1969). The eggs of a female obtained June 11 measured 13 by 27 millimeters (Stebbins 1954). Eggs are laid in May through August, depending on locality, but mainly during June and July. Females may oviposit in alternate years, and only half of the females in a population may lay eggs in any year. Eggs hatch in about two months; hatchling emergence peaks in late July and early August in Colorado (Hammerson 1999). They reach sexual maturity in the second year (Platt 1969). In a Kansas study, only about 30% of the population was as old as 4 years. Maximum longevity in natural conditions is about 8 years, but captive animals have lived two decades.

Apparently the western hognose snake was relatively abundant in Montana during the late 19th Century, at least in some regions; in 1876 it was the third most common reptile (after the western rattlesnake and short-horned lizard) along the Missouri River between Fort Benton and the mouth of the Judith River (Cope 1879). This is no longer the case (Maxell et al. 2003); the few recent records suggest that the species is uncommon throughout Montana, although its status is largely unknown. Even though this snake is still encountered across its historical range, it is less abundant than in the 19th Century probably due to extensive habitat loss associated with conversion of prairie to agricultural landscapes. As in other regions, an unknown percentage of local populations experiences road mortality, as many specimen and observation records are of road-killed individuals. Draining of prairie wetlands may have negative impacts on the prey (toads and frogs particularly, and perhaps turtle eggs) this snake prefers. Management in Montana for this species is hampered by a lack of basic information on abundance, food habits, and habitat associations, but is probably best effected for the long-term by protecting suitable prairie habitats from conversion to agricultural uses. No specific management activities are suggested at this time, but any nests and dens should be protected and left undisturbed.