Spatial‐Mark‐Resight Model to Estimate Raccoon Abundance in Yosemite Valley, California

Prior to 2017 there was a lack of information regarding the abundance and density of raccoons (Procyon lotor) living in Yosemite Valley, Yosemite National Park, California. However, increased awareness of zoonotic disease raised concerns that human-raccoon interactions in Yosemite Valley could pose a risk of disease transmission. Additionally, biologists needed to know if raccoons would threaten the success of an endangered species reintroduction program for the California red-legged frog (Rana draytonii). Our project had several objectives: to obtain a population estimate of raccoons in the Yosemite Valley; to evaluate whether a zoonotic disease risk regarding Baylisascaris procyonis existed; to learn more about the extent of raccoon nuisance behavior; and to consider the risk raccoons may pose to the conservation of the California red-legged frog. We estimated a density of 1.89 (interquartile rate = 1.02-3.14) raccoons/km(2) and a population estimate of 40 individuals (SD +/- 11.5), during Summer and Fall 2017. Three of 6 raccoons sampled showed evidence of B. procyonis infection, indicating a zoonotic risk for visitors to the park. There were 38 recorded incidents of raccoon nuisance behavior. Due to the low estimated raccoon density, we do not expect their presence to be a limiting factor for the California red-legged frog reintroduction program; however, we do suggest that future release sites be located away from known raccoon use areas. We encourage continued attention to wildlife-proof storage of food and garbage, visitor education regarding zoonotic disease risks, management actions aimed at ending anthropogenic feeding, and prompt clean-up of latrine sites found near eating or play areas. (c) 2021 The Wildlife Society.