Functional feeding responses of coyotes, Canis latrans, to fluctuating prey abundance in the Curlew Valley, Utah, 1977–1993

Abstract

We investigated interactions between coyotes (Canis latrans Say, 1823) and prey in the Curlew Valley, Utah, by comparing prey abundances with prey consumption rates. Previous studies reported a cyclic trend in black-tailed jackrabbit (Lepus californicus Gray, 1837) density with a period of 10 years and >150-fold amplitude, as well as short-term fluctuations among some rodent species that exceeded an 8-fold difference in amplitude over 2 years. Our results suggest changes in coyote diets mainly reflect the fluctuations in jackrabbit abundance. Prey switching to rodents during periods of low jackrabbit abundance also was evident. We used the initial feeding pattern analysis to compare prey consumption rates to prey abundance. Coyotes demonstrated a type II (hyperbolic) functional feeding response to changes in jackrabbit abundance. Functional feeding responses to rodent abundances were more difficult to assess because of the strong influence of jackrabbits. In most comparisons, we visually detected a linear functional feeding response to varying rodent abundances; yet this was not statistically supported by Akaike's Information Criterion corrected for small sample sizes (AICc) to assess different models.