How do domestic dogs influence intraguild interactions among native canids?

Abstract

Harvest rates and bowhunter survey data in the Midwestern U.S. suggest both red fox (Vulpes vulpes) and gray fox (Urocyon cinereoargenteus) populations have declined, and a recent assessment of mesocarnivore occupancy across southern Illinois suggested gray fox range was contracting. Indices of coyote (Canis latrans) abundance increased concurrently and competition resulting in intraguild killing and spatial displacement to human-associated habitats have been proposed as agents of gray fox population decline. In addition, we previously demonstrated a strong elevation in both red fox and gray fox occupancy near human-developed areas if coyotes were present. One complication previously unaccounted for in assessing dynamics between coyotes and foxes is the presence of free-ranging domestic dogs (Canis familiaris), commonly associated with anthropogenic habitats. Thus, as gray foxes shift to areas adjacent to anthropogenic habitat to avoid coyotes, they may instead contend with domestic dogs. We utilized an extensive camera-trap data set collected over three years at 1,181 stations across 16 counties in southern Illinois, USA, to evaluate factors influencing species occupancy and interactions between domestic dogs, coyotes, gray foxes and red foxes. Naïve dog occupancy was 0.53 and estimated dog occupancy decreased with distance from structures and municipalities but increased with distance from roads. We found no evidence for species interactions between domestic dogs and coyotes, weak support for a negative interaction between dogs and red foxes, and strong evidence of a negative interaction between dogs and gray foxes. Thus, interacting competitive pressures from coyotes in forest habitats, red foxes in anthropogenic habitats, and the presence of free-ranging dogs along anthropogenic habitat edge, could result in dramatic cumulative impacts to gray fox populations across the region and contribute to the recent decline.