INTRASPECIFIC VARIATION IN WING LOADING AFFECTS HABITAT USE BY LITTLEBROWN BATS (MYOTIS-LUCIFUGUS)

Morphological constraints have been linked to habitat partitioning by different species of animals. Interspecific differences have been expl ored, but less is known about the relationship between individuals of the same species. The purpose of this study was to determine if habita t use by little brown bats (Myotis lucifugus) varies with body mass of individuals. From aerodynamic theory, we predicted that bats with hig her body mass will have higher wing loadings, should be less manoeuvra ble, and thus tend to forage in areas where there are fewer obstacles to detect and avoid (clutter). Habitat was ranked into four zones base d on the degree of clutter, and habitat use was assessed by measuring the time that males and non-reproductive, pregnant, lactating, postlac tating, and artificially loaded females spent in each habitat zone. To test the assumption that a selective advantage accrues to bats foragi ng in clutter, we measured the availability of flying insects in clutt ered and open habitats. Insect trap samples revealed a higher density of insect prey in more cluttered habitats. Body mass was positively co rrelated with wing loading. Overall, males were smaller than females w ith respect to mass and wing loading; however, these differences did n ot translate into differential habitat use. As predicted, there was a significant relationship between individual wing loading and habitat u se, with heavier bats (greater wing loading) foraging in less cluttere d areas.