1991 年 16 巻 1 号 p. 13-25
We investigated seasonal changes in activity of the northern Ryukyu fruit bat Pteropus dasymallus dasymallus from 1988 to 1990 on the island of Kuchinoerabu-jima and also observed the bats in captivity. In the field, the arrival of the first bat at feeding sites occurred 41 min after sunset on average, and it was earlier in spring and summer than in autumn and winter. Feeding started soon after arrival at the feeding trees. The basic pattern of feeding activity was unimodal, and the principal feeding period was observed within 3-5 hrs of arrival. During the second half of the night, feeding activity decreased, and resting or sleeping was more prolonged than during the first half. In winter, the number of bats visiting feeding sites was reduced, and feeding activity was scarcely observed. The time spent sleeping during the night was closely correlated with the ambient temperature, and the duration of sleeping markedly increased when the ambient temperature fell below 10°C. The bats probably reduce their activity levels and their basal metabolic rates during severe winter conditions.
