U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version



Applied Animal Behaviour Science 241 (2021) 105382



U.S. government work


Coyotes (Canis latrans) involved in depredation of livestock, an act frequently resulting in human-wildlife conflict, often do so out of necessity for provisioning pups. Surgical sterilization methods such as vasectomy that preserve gonadal hormones have been successful in reducing depredation by free-ranging coyotes while allowing individuals to maintain territoriality and mate fidelity. However, use of these methods remain costly and ineffective for wide-scale use. Given the alternative proposal of using chemical sterilization techniques, we investigated whether the use of hormone-altering sterilization methods impacted behavior of captive coyote pairs (i.e., male-female pair bonds). Our objective was to evaluate behavior and reproductive hormones of mated coyote pairs that had received different surgical sterilization treatments. We assigned mated pairs of captive coyotes to different sterilization treatment groups (vasectomy, spay, neuter, ovary-sparing spay, and intact) and coded their behavior as the time spent in resting versus active (i.e., walking, running, scent communication, and aggressive interactions) behaviors. Additionally, hormone concentrations were analyzed to determine effectiveness of hormone-altering treatment, given the potential role of gonadal hormones in regulating behavior. The study was repeated across three breeding seasons. The top model comparing time spent active versus resting was the null model, although the model that included whether sterilization type altered hormones and year also had a ΔAIC of < 2.0. Testosterone concentrations between neutered and vasectomized or intact males was significantly different, indicating sterilization treatment was successful and the different sterilization techniques impact hormones differently; there were no statistical difference for estradiol or progesterone levels among female treatment groups. No sterilized pairs produced pups, but the intact pairs did. Although there are potentially some differences in behavior across sterilization treatment types, our results suggest sterilization of coyotes holds potential as a future management strategy as behavior did not differ among different treatments. Potential difference across years suggest further research is necessary to determine potential extraneous factors influencing behavior and the effect of treatment on territoriality on free-ranging coyotes.