Nocturnal and Seasonal Activities of the Pallid Bat, Antrozous Pallidus

Abstract

Nocturnal and seasonal activities of pallid bats (Antrozous pallidus) were observed in central Arizona. The pallid bat night is characterized by two foraging periods with an intervening period of night roosting. Foraging pallid bats have a characteristic style of flight well suited to the taking of relatively large, substrate-roving or slow flying prey. After the initial foraging period pallid bats locate one another through vocal communication and gather in night roosting clusters where they enter torpor. Durations and scheduling of nocturnal activities vary seasonally. Cool months are characterized by smaller colonies of bats, greater fidelity to certain colony sites, slower and later emergence, briefer foraging periods and longer periods of night roosting. Up to 75 percent of the time spent away from diurnal retreats is devoted to night roosting in the autumn. Young are born in June, and during most of the summer adult males do not seem to occur sympatrically with females and young. Females and young appear to forage together in July and August, when little fidelity is shown to roosting sites, large colonies exist, emergence is faster and earlier, and more time is spent in foraging than in cooler months. In mid-August a postbreeding dispersal occurs. These activities and behaviors are discussed in terms of the energetic demands on the bats and the socialization of young.