Nocturnal activity patterns of lactating silver-haired bats (Lasionycteris noctivagans): the influence of roost-switching behavior

A characteristic feature of forest-dwelling bats is that they regularly switch day roosts. The additional time associated with finding or assessing the availability of a new roost, moving offspring to the new roost, coordinating with other group members, and meeting any increased energetic demands that may be associated with these behaviors may influence the number and duration of feeding bouts of reproductive females. To examine the influence of roost-switching on nocturnal activity patterns we radio-tagged lactating female silver-haired bats (Lasionycteris noctivagans) and monitored them on nights when they moved to a new roost site and nights when no roost shift occurred. The typical activity pattern on a non-move night consisted of an initial long bout away from the day roost (median length: 177.4 min) followed by alternating bouts in (50.6 min) and away (57.0 min) from the roost for the rest of the night. On move nights bats reduced the length of their first absent period (82.7 min) and increased the number of trips from the roost, although neither the length of these subsequent absent periods nor the total time absent from the roosts differed from non-move nights. Similarly, total time spent in roosts did not differ between move and non-move nights, but bats made more and shorter visits on move nights. Visits to original and new roosts were not synchronous among colony members, and the length of time for individuals from the same colony to move to a new roost varied from I to 4 h. Our results indicate that roost switching did not influence the total time spent in or away from day roosts. Rather, bats moved between the original roost, the new roost, and foraging areas with much greater frequency on move nights.