Diets of human-subsidized ringtails (Bassariscus astutus) at the Grand Canyon using isotopic niche and fecal analyses

Diets of generalist omnivores can be challenging to describe, particularly when determining the extent to which animals consume anthropogenic food subsidies. However, such insights are essential for understanding trophic interactions in urban ecosystems and reducing human–wildlife conflict. To assess the impacts of human-altered landscapes on Ringtail dietary behavior, we compared the diets of ringtails (Bassariscus astutus) living in Grand Canyon Village—a small municipality within Grand Canyon National Park—to individuals that occupied surrounding natural areas. We used 3 independent methods for comparing Ringtail diet, including stable isotopes from hair, scat dissection, and fecal DNA metabarcoding. The isotopic niche space of ringtails captured in Grand Canyon Village overlapped significantly with human diets (representing a 100% subsidized diet) due to higher δ¹⁵N values, indicating greater protein consumption relative to non-subsidized ringtails from natural areas. Scat dissection verified the use of human foods by ringtails in the village, with anthropogenic materials (e.g., plastic wrappers) detected in 73% of the feces. Fecal DNA results, in addition to scat dissections, indicated similar frequencies of natural food items in Ringtail diets from both areas but provided little evidence of anthropogenic foods. These findings underscore the benefits of utilizing multiple methods when assessing diet and indicate that while urbanized ringtails may acquire additional protein from human foods, subsidy use served to augment overall diet rather than displace consumption of natural foods. For management of nuisance ringtails, human food subsidies may increase human–wildlife conflict, but may not diminish the role of ringtails in natural food webs or their capacity as predators to reduce disease-carrying prey such as rodents.