Assessing springtime vertebrate prey of sympatric mesopredators in the southeastern United States using metabarcoding analysis

Coyotes (Canis latrans) colonized the eastern United States over the last century and formed a 3-species predator guild with bobcats (Lynx rufus) and gray foxes (Urocyon cinereoargenteus) across much of the southeastern United States. Diets among the three species vary along with respective impacts on game species such as white-tailed deer (Odocoileus virginianus) and wild turkeys (Meleagris gallopavo). To determine predation impacts on vertebrate prey and dietary overlap in consumption of prey items, we assessed diets of coyote, bobcat, and gray fox during spring, coinciding with white-tailed deer fawning and wild turkey nesting and brood rearing. We sampled across three sites along the Savannah River in South Carolina from mid-May through mid-June of 2020-2021. We collected 180 scat samples along 295.9 kilometers (71.1-122.4 km/site) of unpaved secondary roads and used DNA metabarcoding to determine vertebrate diet items. We identified predator species of scat using DNA metabarcoding and species-specific mtDNA fragment analysis (153 were coyote, 20 bobcat, and seven gray fox). Overall, we found evidence that two species, coyote and bobcat, consumed deer while all three consumed turkeys. Frequency of deer in the diet varied across sites for coyotes from 62-86% and wild turkey was present with a frequency of occurrence of 9% for coyotes, 5% for bobcats, and 14% for gray fox. Vertebrate diet specialization was evident across predator species with high frequency of deer in coyote diets, rabbits and small mammals in bobcat diets, and herpetofauna in gray fox diets. During deer fawning and wild turkey nesting and brood rearing, dietary overlap appears to be mediated by disparate selection of prey items, which reduced competition among coyotes, bobcats, and gray foxes. Use of DNA metabarcoding may augment our understanding of dietary preferences within this predator guild by providing increased resolution of diet composition among important game species.

Diet reveals potential for competition and coexistence among coyotes (Canis latrans), red foxes (Vulpes vulpes), and gray foxes (Urocyon cinereoargenteus)

Species can alleviate competition by reducing diet overlap. Non-native coyotes (Canis latrans Say, 1823) and historically native gray foxes (Urocyon cinereoargenteus (Schreber, 1775)) have expanded their ranges and may compete with native red foxes (Vulpes vulpes (Linnaeus, 1758)). To examine potential competition among canids in Maine, USA, we compared δ13C and δ15N from muscle and hair samples to assess relative resource use, and we compared frequency of occurrence of prey items from stomach contents to assess diets. For these species, red foxes consumed anthropogenically based foods the most in fall and early winter, gray foxes consumed anthropogenically based foods the most in summer, and coyotes consumed anthropogenically based foods the least in all seasons. Coyotes held the highest relative trophic position in fall and early winter, red foxes held the highest relative trophic position in summer, and gray foxes held the lowest relative trophic position. Based on stomach contents, gray foxes had the broadest diet and consumed the most plants, and coyotes had the narrowest diet. Red foxes were the only species to show isotopic niche overlap with both potential competitors across seasons. Thus, they may be most susceptible to competitive exclusion among these canids, with implications for community dynamics as ranges shift due to human activity.