The effect of urbanization on spatiotemporal interactions between gray foxes and coyotes

Abstract

Interactions between species can influence their distribution and fitness, with potential cascading ecosystem effects. Human disturbance can affect these competitive dynamics but is difficult to measure due to potential simultaneous spatial and temporal responses. We used camera traps with a multispecies occupancy model incorporating a continuous-time detection process to evaluate spatial and temporal interactions between two competing carnivore species, coyote (Canis latrans) and gray fox (Urocyon cinereoargenteus), along an urbanization gradient. Coyotes were less likely to occupy high housing density sites than gray foxes, but the two species were more likely to co-occur in suburban forest fragments. Gray foxes were less likely to occupy low housing density sites in the presence of coyotes, shifted their activity patterns to be more nocturnal when coyotes were present and avoided sites recently used by coyotes. These effects were most pronounced where forest cover was low, suggesting these shifts are not necessary where forest cover is high, perhaps due to the gray fox's ability to climb trees. Gray foxes did not spatially or temporally avoid coyotes moving through the suburban matrix nor did precipitation mediate temporal avoidance in suburban habitats (i.e., by washing away scent), possibly because coyotes are less likely to establish territories at high housing densities, and thus less likely to scent mark. As reports of gray fox declines in portions of North America mount and coyotes are implicated, our results suggest that preserving tree cover could be important for gray fox persistence. At least 50% of forest cover in a 1 km radius resulted in lower coyote occupancy with gray fox occupancy rising to ≥0.1, suggesting a good benchmark for management.