The Effect of Reproductive Condition on the Foraging Behavior of Female Hoary Bats, Lasiurus cinereus

Female mammals experience large changes in time and energy budgets associated with reproduction and these may influence the foraging strategies of individuals. I studied the changes in foraging behavior associated with reproduction in female hoary bats, Lasiurus cinereus. As lactation progressed, individuals departed to forage earlier in the evening and spent more time foraging per night and less time roosting with their young. Foraging time increased by at least 73% between early lactation and fledging and then declined as the young became independent. Females with two young foraged for longer than did those with one and females with pre- and postfledging young foraged in different habitats. The changes in foraging time suggest that foraging activity of female L. cinereus is constrained and individuals act as time minimizers, adjusting their foraging behavior to meet current energy demand. Predation risk is unlikely to constrain the behavior of these bats. However, maximizing energy intake throughout lactation may not be the optimal strategy because storaging excess energy increases flight cost and may reduce foraging efficiency. The need to keep newborn young warm may also influence foraging time. Such constrains, causing changes in foraging activity, may alter the availability of habitats and prey and must be considered when modelling foraging strategies. In addition, changes in flight time may significantly alter the energy budgets of bats in different stages od reproduction.