Bullsnake. Pituophis catenifer

Description: A large snake with a long, stout body and a moderately long tail. Total length ranges from 900-2,000 mm, with individuals generally being larger in the southern parts of the range. There are usually four prefrontal scales. There are no facial pits and the rostral scale is not upturned. The dorsal scales are keeled, in 27-37 rows at mid-body. The anal scale is single. There is no rattle on the tail. The general colour is yellowish, with black, brown or brick red dorsal blotches and rows of smaller lateral spots or dashes. The ventral scales are usually checkered brown and cream.

Variation: Males may be larger than females. Males mature at one to two years, females at three to five years.

Natural history: It is mostly found in the drier areas of grassland or sagebrush, and may be found in farmlands and fields. It is typically found in areas of sandy soil, frequently in association with rock piles or boulders. It is diurnal or crepuscular (active at dawn and dusk). It is able to both burrow and climb. When molested it hisses loudly strikes and may vibrate its tail. Individuals will almost certainly bite if handled. While not venomous, the bite may be quite painful. It is a generalist feeder and eats rodents, rabbits and other small mammals, birds, nesting birds and bird's eggs, lizards and arthropods. It kills by constriction and dens in the winter.

Reproduction: Males may engage in combat during the mating season. During copulation the male lies along and on top of the female and usually bites her on the back and neck. One or two clutches of between two and twenty-four eggs are laid each summer. Nest sites are often abandoned mammal burrows on south-facing slopes. The incubation period is fifty to sixty days. Hatchlings are between 200 and 400 mm total length and emerge from the eggs in late summer or early fall. The hatchlings may not feed until the next spring.

Distribution: In Alberta, the bullsnake is limited to short-grass prairie. It extends north from the Montana border to the Trochu region, and west from the Saskatchewan border to a line connecting Calgary with Waterton. It is found at elevations up to 2,000 m. Extralimitally, it occurs over much of the central and western United States and northern Mexico. Its range is fragmented in the Rockies of the United States and east of the Great Plains.

Conservation status: In the areas of Alberta in which it occurs the bullsnake is still frequently encountered and does not appear to be in decline, although its range is considerably more constrained than it appears to have been in the early years of the century.

Remarks: Six subspecies are recognized in Canada and the United States. Pituophis catenifer sayi occurs in Alberta. The range of this subspecies extends from Alberta and south western Saskatchewan south to north eastern Mexico, and west from the Idaho panhandle to western Indiana. It is probably the most economically beneficial snake in Alberta as it plays an important natural role in pest control. Although some authors (Sweet and Parker 1990; Conant and Collins 1991) place this species in P. melanoleucus, we here follow Collins (1997) in referring it to P. catenifer.

Significant references: Bullock 1981; Bullock and Tanner 1966; Burger 1991; Carpenter 1982; Clark and Chandler, 1992; Clark and Bradford 1969; Cook and van Zyll de Jong 1975; Corn and Bury 1986; Diller and Wallace 1996; Fitch 1985; Greenwald, O.E. 1971; Licht and Bennett 1972; Packard and Packard 1988; Parker and Brown 1980; Pendlebury 1972,1973; Stinner 1987; Sweet and Parker 1990.