Community-level effects of coyote population reduction

Predator control in the United States is directed primarily at the coyote (Canis latrans). Control programs are constructed to relieve predation losses to livestock. Although a variety of nonlethal control techniques are being used to some degree, lethal control methods continue to be a major part of modern predator control programs. Toxicants have played a major role in past coyote population reduction programs. Traditional toxicants included strychnine, thallium sulfate, sodium cyanide, and sodium fluoroacetate (compound 1080). The use of toxicants on federal lands was banned by presidential order in 1972; this ban was revoked in 1982. Toxicants may play a larger role in predator control programs if the U.S. Environmental Protection Agency approves registration of any old or new materials for that purpose. There appears to be an inverse relationship between population levels of coyotes and red foxes (Vulpes vulpes), gray wolves (C. lupus), or other carnivores. When large-scale coyote population reduction programs were successful, red foxes and other medium and large mammalian predators tended to increase. Experimental work and observations on coyote and red fox interactions have shown that coyotes exclude foxes from coyote-occupied habitats. Thus a single-species population reduction program, with toxicants or other means, impacts other members of the medium and large mammalian carnivore guild. The resulting change may impact prey species, because of species-specific prey preferences and foraging tactics, but this is poorly documented. This paper reviews historical trends of populations of North American canids and recent work on interspecific interactions of canids. In addition, it examines three ecological mechanisms that may be major factors leading to canid competition