Winter Behavior of Pronghorns in Relation to Habitat

Abstract

The winter behavior of pronghorn antelopes (Antilocapra americana) was studied from 6 January to 12 April 1969 in southeastern Alberta and northern Montana. January, climatically an exceptionally severe month in the study area, saw a pronounced movement of pronghorns southward. The mean herd size was 39.8 11.5 head. Herds did not mix, nor move more than a few km from local sites during February and March; a distinct disbanding process was noted after 25 March. Fences and roads limited day to day movements. Herd composition counts for 6 herds (221 head) indicated a low fawn proportion (41 fawns to 100 does). The male to female fawn ratio of 42 to 100 indicated poor production or survival of male fawns. Pronghorns were adept at pawing away snow cover to reach their food. They spent 6.2 to 11.5 percent of their feeding time pawing. Interactions at feeding craters and bedding sites indicated a social heirarchy with male adults at the top, followed by female adults, and fawns. Pronghorns selected microhabitats with more favorable conditions than the average for the area as a whole, these being: 63 percent lower wind velocities, 24 percent less snow, and 87 percent softer snow. The daytime activity pattern began with a feeding period shortly after sunrise. Resting animals oriented the longitudinal axis of the body so that their anterior portions were downwind when chill factors were extreme; they also curled their heads alongside the body more often at lower chill factors. J. WILDL. MANAGE. 41(3):560-571 Few efforts have been made to determine how wild ungulates have adapted their behavior to winter conditions. Pruitt (1959) has shown that snow influences much of the behavior of caribou (Rangifer arcticus). Henshaw (1968) confirmed much of this with supporting data for Alaskan caribou. In Quebec, DesMeules (1964, paper presented at N.E. Wildl. Conf., Hartford, Conn.) learned that moose (Alces alces) capitalize on the insulating properties of loose fluffy snow when selecting bedding sites. They also travel under large conifers where the snow is less deep. Verme (1968) was able to demonstrate that temperature and wind were the major climatic factors causing heat loss in white-tailed deer (Odocoileus virginianus) in normal habitat. Moen (1968) concluded that behavior of animals may easily turn a negative heat exchange into a positive one. The objective of this research was to determine the winter behavioral adaptations of pronghorn antelopes. I am indebted to V. Geist for his support, valuable suggestions, and criticisms. Gratitude is also expressed to my wife, E. Scheinberg and D. R. Flook for their assistance.