Surgical Sterilization of Coyotes to Reduce Predation on Pronghorn Fawns

Abstract

Sterilization of coyotes (Canis latrans) has been shown to reduce predation of domestic sheep. We investigated whether sterilizing coyotes would similarly reduce predation on pronghorn (Antilocapra americana) neonates in southeastern Colorado. In a study from May 2006 to March 2008, we radio-collared 71 pronghorn fawns to determine survival rates and causes of death. During the first year of the study, all coyotes were intact. During the second year, we captured and sterilized coyotes in the southern half of the study area, while coyotes in the northern half were given sham sterilizations. In addition, we surveyed the availability of alternative prey and examined the influence of snowfall and precipitation on fawn survival and small mammal detection. Using the known fate model in Program Mark, we constructed models that included a treatment effect, plus year, area, alternative prey, and individual covariates to estimate fawn survival. Fawn survival was higher for fawns captured in sterile coyote home ranges than for fawns captured in intact coyote home ranges (P = 0.078). Subtle differences in locale affected fawn survival; fawn survival was higher in the north than in the south in both years (P = 0.081). Lagomorph abundance was not influential on fawn survival (P = 0.293) nor was rodent abundance (P = 0.264), but increased vegetation may have impaired prey detection probabilities. We did not detect any relationship between fawn survival and fawn gender, fawn birth weight, fawn birth date, fawn age, or coyote density 1 Co-authored by Eric Gese and Mary Conner. 11 (P > 0.110). Although in the second year of the study we experienced record winter conditions, this did not reduce fawn survival and may have contributed to increased fawn survival (P = 0.364). Our results indicate that sterilization of coyotes may be a useful tool for wildlife managers to reduce coyote predation on pronghorn fawns.