SEX-BIASED PREDATION ON MOTHS BY INSECTIVOROUS BATS

Two species of insectivorous bats, Lasiurus cinereus and L. borealis, ate significantly more male than female moths in the wild. The observe d bias was likely to be a consequence of sexual dimorphism in moth fli ght activity associated with sexual differences in mate acquiring mech anisms. Female moths flew less than males and their activity peaks occ urred at different times. The peak of male activity coincided with a p eak in bat activity in the middle of the night, while female activity peaked earlier in the night when bat activity was relatively low. The results of this study are interpreted in a sexual selection framework, and the conclusions about predation risk from bats that hunt airborne prey are applicable to all nocturnally flying insects that exhibit se xual dimorphism in flight activity.