Comparison of seasonal changes in body weight of raccoon dogs between the warm and cool temperate zones in Japan

Abstract

Mammals in the warm temperate and boreal zones typically deposit body fat prior to the onset of winter. A recent study from Wakayama, Japan, located in warm temperate zone, showed that raccoon dog (Nyctereutes procyonoides) body weight increased by 21% in October. To determine how this increase may change in different climate zones, we assessed body weight increase in raccoon dogs (n = 192) in and near Tokyo, Japan, which is located in a cool temperate zone. The body weight increased by 37% in October, and the kidney fat index (n = 152) peaked during this month. This was likely caused by the diet, as raccoon dogs in this region feed mainly on insects during the summer, but switch to feeding exclusively on fleshy fruits during autumn. We conclude that the autumn weight increase in raccoon dogs is greater in the cool temperate zone than in the warm temperate zone in Japan.