Distribution, Habitat Selection, and Diel Activity Patterns of Four Introduced Carnivores on Okushiri Island, Hokkaido, Northern Japan

Invasive mammalian predators are the most damaging alien animal species in terms of biodiversity, particularly in island fauna. Currently, four mammalian carnivores (raccoon dogs, feral cats, American mink, and masked palm civets) have been introduced to Okushiri Island, Hokkaido, northern Japan; however, basic information for invasive species management such as their distribution and activity patterns on the Island are still unclear. This study aimed to reveal the distribution, habitat selection, and diel activity patterns of alien carnivores on Okushiri Island. Camera trapping was conducted at 31 sites from June to November 2022. We evaluated the diel activity patterns using the kernel density method and habitat selection using a generalized linear mixed model. During the 2094 camera days, we obtained the occurrence frequencies of 4105 raccoon dogs, 208 masked palm civets, 71 feral cats, and 69 American mink. The raccoon dog was active at night and day and avoided streams. The masked palm civet was only active at night, preferred grasslands, and avoided residential areas. The American mink was active at night and day and preferred streams. The feral cat exhibited crepuscular patterns and preferred residential areas. Our study revealed that raccoon dogs have a high population density on Okushiri Island.