Does communal nesting help thermoregulation in Japanese flying squirrels (Pteromys momonga) in winter?

Communal nesting is suggested to assist with thermoregulation in tree squirrels and flying squirrels in temperate and subarctic zones during winter. We tested the thermoregulation hypothesis as an explanation for the ecological function of communal nesting in Japanese flying squirrels (Pteromys momonga). We observed their nesting behavior using video camera traps. Pteromys momonga is endemic to Honshu, Shikoku, and Kyushu, Japan. The study was conducted from December 1, 2017 to November 30, 2019 in the northern part of the Kiso Mountains, Nagano Prefecture, Japan. During the snowy season, the number of flying squirrels nesting in a cavity varies daily. The fluctuation in the daily maximum number of individuals nesting communally did not correlate with ambient temperature, suggesting that communal nesting may not always be related to thermoregulation.