Coyote diet patterns in the Mojave Desert: implications for threatened desert tortoises

Abstract

Coyotes (Canis latrans) are generalist predators and are ubiquitous in North America. Occasionally, predation by coyotes can pose a threat to populations of rare species. We assessed diet patterns of coyotes over a 5-year period (2009–14) in a region of the Mojave Desert where high predation rates on threatened desert tortoises (Gopherus agassizii) had been reported. Our goal was to identify primary food items for coyotes and to assess the importance of desert tortoises in the diet. Coyotes primarily consumed rabbits and rodents with rabbits being consumed preferentially and rodents, along with secondary foods including various birds, reptiles, arthropods, and fruits, being consumed more opportunistically. In response to low annual precipitation in the last three years of the study, dietary diversity increased, as did use of anthropogenic food items by coyotes. However, coyotes did not seem to be dependent upon anthropogenic items. Remains of desert tortoises occurred in coyote scats at low frequencies (<6%) in all years and seasons, and use of tortoises appeared to be opportunistic as use varied with tortoise abundance. In the portion of the study area where 571 translocated desert tortoises had been released in 2008, the frequencies of tortoise remains in coyote scats were markedly higher in the two years following the releases (7.5% and 8.8%, respectively). The high predation rates on tortoises reported in this area may have resulted from focussed coyote foraging efforts due to the availability of vulnerable individuals (e.g. disoriented and displaced tortoises) as well as higher tortoise densities.