Studies on the Physiological and Ecological Adaptation of Temperate Insectivorous Bats : III. Annual Activity of the Japanese House-dwelling Bat, Pipistrellus abramus

A study on annual activity cycle of P. abramus was carried out in Fukuoka City. The bats formed a colony and remained in one house all year, without seasonal migration. From May to September emergence time of the first bat averaged 12 minutes after sunset, though it was earlier in cloudy weather than in clear. As for nocturnal activity, there was both a major peak soon after sunset and a minor peak just before sunrise from May to August, but in October only the former occurred. When air temperatures dropped to 15℃ and less, bats seldom emerged. The principal foraging period was within 2 or 3 hours after emergence in summer; and was synchronized with the emergence of most small Lepidoptera and Coleoptera, which constitute the major portion of the diet. In early spring and autumn Diptera became the main food. The size (body length) of available insects was 15mm and less. The increase ratios of body weight in late autumn to that in summer were 30.6 and 29.2 % in adult females and males, respectively. Hibernation lasted from early November until mid-March. During deep hibernation, arousal occurred once in 16 days, and the rate of weight loss (ca. 1 mg/g body weight/day) was about half of that during the shallow hibernation. Winter activities of genus Pipistrehs are various in different species. It may be attributed not only to variations in climate and food, but also to the degree of coldresistance and of torpidity.