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


Date of this Version

February 2001


Published in Can. J. Zool. 79: 386–392 (2001).


Predation on sheep by coyotes (Canis latrans) is a longstanding problem for sheep producers. Current research suggests that surgical sterilization of coyotes could prove to be an effective method of reducing their depredation rates on domestic sheep by modifying their predatory behavior. However, for sterilization to be a viable management tool, the territorial and affiliative behaviors of pack members would need to remain in place. We tested whether surgically sterilized coyotes maintained pair bonds and territories in the same manner as intact coyotes. We also examined if territory fidelity and survival rates differed between sterile and intact coyotes. From June 1997 to April 2000, 10 males and 9 females were sham-operated and radio-collared, while 20 males and 6 females were surgically sterilized and radio-collared. We monitored members of 5 sterile and 4 intact packs during 1998, 6 sterile and 7 intact packs during 1999, and 4 sterile and 6 intact packs through the 2000 breeding season. Behaviorally, sterile packs appeared to be no different than intact packs. A half-weight association index showed that social dyads within sterile coyote packs were located together as frequently as dyads within intact packs. Simultaneous radiolocations of members of sterile packs showed that members of sterile packs were significantly closer to each other than would be expected from random locations. There was no difference in size or degree of overlap between territories of sterile and sham-operated coyote packs. Sterile coyotes had a higher annual survival rate than reproductive animals in 2 of the 3 years, and there was no difference in the level of territory fidelity. We concluded that surgical sterilization did not modify the territorial or affiliative behaviors of free-ranging coyotes, and therefore sterile coyotes could be used as a management tool to exclude other potential sheep-killing coyotes.