Bioenergetics of Japanese monkeys (Macaca fuscata) on Kinkazan Island during winter

Abstract

An adult female Japanese monkey was chosen as a focal animal in order to assess the nutritional condition of the species during winter on Kinkazan Island, which is covered by deciduous forest of the cool temperate zone. Five whole-day-long observations were performed at the end of November (late autumn) and also at the end of February (late winter).

In November, the daily energy intake and protein intake were estimated to be 1,449 kcal and 36 g, respectively: both satisfied the intake requirement even in view of a digestibility of 55%. These findings suggest that the focal animal could accumulate body fat in November. In contrast, in February, the daily energy intake and protein intake were estimated to be 556 kcal and 12 g, respectively: both did not satisfy the intake requirement in view of a digestibility of 55%. These findings suggest that the focal animal consumed accumulated body fat in February.

Various data for food intake, nutritional content, etc. on Kinkazan were compared with those on Koshima, which is covered by evergreen forest of the warm temperate zone. The nutritional intake in February on Kinkazan was much smaller than that in November on Kinkazan as well as those in November and February on Koshima. The small intake of the former appeared to be strongly influenced by the sign ficantly lower speed of dry weight intake, which derived partly from the significantly lighter unit weight of the food items (e.g., buds ofZanthoxylum piperitum, Castanea crenata, andCornus macrophylla; leaves and stems ofOplismenus uadulatifolius andZoysia japonica). The monkeys on Kinkazan Island increased their food diversity, shortened their daily travel distance, and avoided repeated use of sites within their home range to offset the deterioration of the food quality in February.