Population Ecology of Coyotes during a Fluctuation of Snowshoe Hares

Abstract

Functional and numerical responses of coyotes (Canis latrans) to a cyclic fluctuation of snowshoe hares (Lepus americanus) were studied in a mixed farming-boreal forest ecosystem. Winter coyote densities on the 180-km2 study area near Rochester, Alberta, were directly related to hare abundance. The amplitude of the coyote fluctuation was 3-6-fold (vs. 20-40-fold for the hare). Percent biomass of hares in the coyotes' winter diet varied from 0 to 77; 94% of the variation was attributable to changes in hare density. Large mammals, chiefly livestock carrion, were the most important alternate foods during periods of hare scarcity. Coyote association with open areas (nonhabitat for snowshoe hares), and their proximity to settlement, were inversely related to hare abundance over the course of the cycle. During 3 years of hare population decline, breeding by yearling female coyotes declined over 50%; mean litter size declined over 25% among adult females. Litter size among yearlings was probably unaffected by hare population trends. J. WILDL. MANAGE. 45(3):629-640 Cyclic fluctuations of northern coyote populations have been documented by fur returns since the early 1900's (Keith 1963), and have been shown to reflect the 10-year cycle of the snowshoe hare. However, there have been no long-term field studies of functional and numerical responses of coyotes to changing snowshoe hare abundance. Information on coyote population ecology in the boreal forest is likewise scant. Our studies of coyote populations near Rochester, Alberta, began in 1964. That work was part of an integrated long-term research program on the 10-year cycle of snowshoe hares, tetraonids, and predators in the boreal-forest ecosystem. Winter coyote numbers were monitored from 1965-66 through 1974-75; intensive coyote studies were of shorter duration and occurred during 2 periods. Results from the 1st period (1964-68), extending from a low to the early recovery of hare populations, were summarized by Nellis and Keith (1976). The 2nd period of intensive study (1971-75) was during a hare population decline from the cyclic peak in 1970-71. Keith et al. (1977) briefly summarized functional and numerical responses of coyotes (and other predators) to changes in hare numbers in the Rochester area during 1965-75, and examined the impact(s) of predation on the hare population. This paper summarizes all available information on demography and ecology of coyotes at Rochester during 1964-75. Some data from coyote population studies conducted on another area near Westlock, Alberta, during 1967-68 through 1974-75 are also summarized. Financial support was provided by the University of Wisconsin College of Agricultural and Life Sciences, and the Research Committee of the Graduate School; the Fish and Wildlife Division of the former Alberta Department of Lands and Forests (now Energy and Natural Resources) and the Plant Industry Division of the Alberta Department of Agriculture; 1 Present address: Department of Energy and Natural Resources, Edmonton, Alberta T5K 2C9, Canada. 2 Present address: RR 1, Onoway, Alberta TOE 1VO, Canada. J. Wildl. Manage. 45(3):1981 629 This content downloaded from 207.46.13.83 on Fri, 13 May 2016 07:16:15 UTC All use subject to http://about.jstor.org/terms 630 POPULATION ECOLOGY OF COYOTES* Todd et al. the Research Council of Alberta; the Wisconsin Alumni Research Foundation; and the National Science Foundation. We are grateful for the field and laboratory assistance of E. Anderson, C. J. Brand, L. C. Giesbrecht, H. O. Johnson, D. Keith, R. Munstermann, D. Painter, J. L. Pease, K. W. Sloman, D. M. Todd, E. Vowles, and L. A. Windberg. We thank the hunters and trappers who cooperated with us during the study, C. H. Nellis for access to published and unpublished data from 1964-68, and M. J. Dorrance for helpful comments on an early draft of the manuscript.