Winter weather conditions result in temporal niche overlap among three sympatric medium-sized carnivores in northeastern Japan

Temporal niche partitioning may be influenced not only by interspecific competition, but also by weather conditions. Decreased food availability and dietary overlap between species can increase the degree of interspecific competition during winter, thereby promoting temporal niche partitioning. However, multiple species can be simultaneously active under similar weather conditions (high temperature and little snowfall) in winter to reduce energy costs and increase temporal niche overlap. In this study, we aimed to determine the degree of temporal niche partitioning among red foxes ( Vulpes vulpes ), raccoon dogs ( Nyctereutes procyonoides ), and Japanese martens ( Martes melampus ), and its variation with seasonal climate change in terms of interspecific competition and weather conditions. We obtained data on the target species through a camera-trap survey conducted in a heavy snowfall area in northeastern Japan. We analyzed the degree of temporal niche partitioning based on diel activity overlap, co-occurrence rates per night, and behavioral avoidance within 1 or 2 h. We also evaluated the relationship between the presence or absence of activity per night and nightly weather conditions (temperature, precipitation (snowfall), moonlight). We observed a high degree of temporal niche overlap among the three species. In particular, the degree of temporal niche overlap was higher in winter than that in other seasons because the activity of the three species was greatly affected by low temperatures and snowfall in winter. As a winter survival strategy, coping with the weather may be more important than avoiding competition. Our results conflict with the hypothesis predicting temporal niche partitioning in winter, suggesting that weather effects can be an important factor in varying temporal niche partitioning among carnivores. Significance statement This study revealed that the temporal niche overlap of three carnivores in northeastern Japan was higher in winter than that in other seasons because they were simultaneously active under similar weather conditions (high temperature and little snowfall) in winter to reduce energy costs. This indicates that coping with the weather may be more important than avoiding interspecific competition as a winter survival strategy. Our results conflict with the hypothesis predicting temporal niche partitioning among carnivores in winter due to restricted food resources and dietary overlap. This suggests that the different degre