Onset of Volancy and Foraging Patterns of Juvenile Little Brown Bats, Myotis lucifugus

Abstract

In this paper I quantify and compare patterns of use of habitat and diet of adult and juvenile little brown bats ( Myotis lucifugus ). Individuals were captured in mist nets as they foraged. Clutter indices (CIs) ranging from 0 (least cluttered) to 5 (most cluttered) were used to categorize feeding microhabitats based on density of vegetation. A total of 378 M. lucifugus was banded over a 2-year period and dietary analysis was performed on fecal samples from 90 individuals. Foraging patterns of juveniles and adults differed significantly, and patterns of adult were density dependent. When population density was high, adults moved from foraging primarily in open areas close to the ground (CIl) to semiclutter and heavy clutter microhabitats (CI3, CI4, and CI5). Adults shifted foraging areas in mid-July when juveniles developed volancy. When density of the population was low (the result of a population crash at the site), adults foraged in CIl throughout summer and did not shift habitats. Juveniles foraged predominantly in the least-cluttered microhabitat (CIO) in both years independent of density of population.