Niche Separation of Sympatric Carnivores—Red Foxes (Vulpes vulpes) and Japanese Martens (Martes melampus)—In Northern Japan

Studying mechanisms that enable multiple carnivores to coexist is essential to understanding their relative trophic impact in ecosystems. Here, we compared seasonal dietary composition and diversity, relative abundance, and diel activity of wild red foxes (Vulpes vulpes) with those of sympatric Japanese martens (Martes melampus) to address coexistence mechanisms of multiple carnivores in a temperate region. Between 2022 and 2023, we performed field surveys in Ishinomaki City, northern Japan, during which we conducted fecal analyses and camera trapping. Foxes predominantly fed on mammals (percentage area in fecal samples: 58%), fruits (17%), and birds (14%), whereas martens depended more on fruits (71%) and insects (14%). The dietary diversity of foxes was greater than that of martens, except in spring. Foxes were not detected by camera traps in spring, likely because of their home range expansion during this food-scarce season, whereas such seasonality was not found for martens. Finally, foxes were active throughout the diel period, whereas martens were crepuscular. In summary, 1) dietary, 2) spatial, and 3) temporal partitioning enables foxes and martens to coexist. Such findings on segregation across multiple niches in sympatric carnivores from the temperate region are key to our integrative understanding of coexistence mechanisms in carnivores.