The foraging strategy of Asiatic black bears Ursus thibetanus may change in summer and fall, because bears undergo hyperphagia in fall. The changes in gut retention time (GRT) may affect intervals of foraging bout and frequency, and consequently the behavior of bears. Therefore, the aim of this study is to compare GRT of bears in summer and fall, and also compare GRT with different amount of food supply.

The experiment was conducted at Ani Bear Park in Akita prefecture, in summer and fall, 2010-2011. Following 5 days of habituation, 5 patterns of food supply (Actinidia fruits fed ad libitum and restricted in summer and ad libitum in fall, Quercus acorns fed ad libitum and restricted in fall) was fed to 3 adult male bears for each pattern. GRT was estimated by feeding the bears 200 plastic beads with the food and after, the time of defecation and the number of beads in each feces were counted.

GRT was longer in summer than in fall, when the bears were given Actinidia fruits ad libitum. This indicates that bears modulate their GRT to increase food consumption in fall. GRT did not differ significantly when the bears were given different amount of food supply in both summer and fall.