Abstract
Though body weights of bears are known to change seasonally responding to nutritional conditions, there is little information on the body weight and nutritional condition of Asiatic black bears, Ursus thibetanus. We weighed seven female Japanese black bears, U. thibetanus japonicus, under captive condition from May to December, 1995. Although the body weights did not differ significantly between years, three seasonal phases were distinguishable according to the increase rate (rw). During Phase I, mean body weight increased gradually from May (46.2±4.4 kg, mean±SD, n=6) to August (57.3±3.5 kg, n=6: 5%<rw<10%). From August to November, the mean body weights were stable (59.4±4.3 kg, n=4: rw<5%). Contrary, body weights increased rapidly during November and December (68.4±4.7 kg, n=5: 10%<rw). The gradual body weight increase in the Phase I was probably because of sufficient food and lower energy expenditure, while the rapid increase in Phase III seems to be an adaptation for hibernation.
