Variation in coyote social organization: the influence of prey size

Abstract

The foraging ecology and social organization of coyotes, Canis latrans, were studied in Jasper National Park, Alberta, from 1974 to 1977. Diet was determined from analysis of 1967 feces. In summer when rodents (43%) and neonatal cervids (19%) were the major foods, average group size in the population was 1.4 (n = 339 observations), whereas in winter when large ungulates dominated the diet (67%) average group size rose to 2.0 (n = 798). This pattern was also evident for two packs where mean group size rose from 1.5 in summer to 3.1 in winter with the incorporation of pups into the pack. The percentage of mule deer in the winter diet varied directly with group size. Packs were more successful than pairs or single coyotes in catching mule deer. In contrast, the percentage of elk in the winter diet was independent of group size. Since elk were scavenged, their occurrence in the winter diet was primarily a function of the number dying within each coyote territory. Pairs and packs defended ungulate carcasses and used these clumped resources more effectively than single coyotes. I conclude that group foraging increases the feeding efficiency of coyotes in Jasper. A comparison of the present findings with the results of the other coyote studies indicates that variation in the average size of prey eaten is an important factor determining group size and structure of coyote populations.