Prey Phenology of Invasive Raccoon on Three Frogs During Temporal Breeding Period

Abstract

Japan has a high diversity of amphibians; however, there are concerns that native species may become extinct due to habitat degradation and invasive species. Raccoons, which prefer wetland habitats, have caused population declines in amphibians, even those with short breeding periods. We evaluated the hypothesis that raccoons appear in wetlands and predation events increase according to the timing of amphibian breeding. In particular, we evaluated differences in the presence of raccoons in wetlands depending on the breeding status of various frog species, accounting for spatiotemporal autocorrelation. From May to July 2022, January to July 2023, and January to February 2024, we monitored animal and frog calling levels using camera traps at 28 sites in Aina Satoyama Park, Hyogo Prefecture. We constructed a generalized linear mixed model with the number of raccoon appearance events and average estimated staying time as objective variables and presence or absence of breeding frogs of each species on the day and previous day, number of egg masses, and month as explanatory variables, using a poisson distribution and tweedie distribution accounting for spatiotemporal autocorrelation. The both best models based on Akaike’s information criterion values included the breeding of Rana japonica on the day, breeding of Zhangixalus schlegelii on the previous day, egg masses of R. japonica, and month. Our results suggest that raccoons form an association between frog calls or breeding days and prey resources.