Effects of 1988 Fires on Ecology of Coyotes in Yellowstone National Park: Baseline Preceding Possible Wolf Recovery

Abstract

Sixty-five healthy coyote (Canis latrans) adults and 53, 8-12 week old pups captured at dens were radio-tagged in the Lamar Valley and Blacktail Plateau areas of the northern range of Yellowstone National Park. Adults range in age from 1 to 11 years and averaged nearly 3 years old. Territorial packs in both study areas are adjacent, non­overlapping, contiguous, and averaged 15 km2. Based on information the last three winters and data collected from 1946 to 1949, territorial areas are traditional and have changed little in the last 45 years. We estimate that 85 to 90% of coyotes on the northern range belong to packs. A territorial group or pack during the winter consists of 2 alpha individuals, 2 or 3 beta adults, and 2 or 3 adult-sized pups (average pack size = 7). Only one radioed adult coyote has died since May of 1992. Twenty­ four of 53 pups have died between the ages of 3 and 9 months old. Population productivity ranges from 1.8 to 2.5 pups recruited per territory. The reproductive failure rate among breeding groups averaged 15% during 1990 and 1991. Initial density estimates are 1.4 coyotes per square mile. Intensive foraging observations were conducted from January through June 1991 (353 hours) and from November 1991 through April 1992 (1100+hours). Focal observations collected from January-June 1991 resulted in 427 capture attempts on small mammal prey with 162 (38%) successful. Habitat type played a key role in the success rate. Preliminary analysis of the November 1991 to April1992 data indicated a substantial reduction in prey attempts and prey success. This reduction was mostly a function of harsh snow conditions in early winter and abundlint elk carrion in late winter. Over eighty ungulate carcass were located this winter in the 2 study areas. However, small mammals, especially voles, dominate the diet with ungulate remains becoming important in May through July (presumably elk calves) and late winter (mostly scavenging). We have documented numerous successful and unsuccessful predation attempts on ungulates in our study areas. Coyotes appear to impact ungulate numbers in 3 ways: predation on calves and fawns shortly after birth (up to 8 weeks), predation on short-yearlings and adults during winter, and indirect impact from harassment of other predators at ungulate-kills. Coyotes may be the major ungulate predator on the northern range due to cooperative social and foraging behavior, their ability to take advantage of vulnerable ungulates, and their high population levels. Wolf extirpation has probably resulted in high coyote population densities and coyotes have, at least, partially slid into this vacant niche.