Discrimination of wingbeat motion by bats, correlated with echolocation sound pattern.

Bats of the species Rhinolophus rouxi, Hipposideros lankadiva and Eptesicus fuscus were trained to discriminate between two simultaneously presented artificial insect wingbeat targets moving at different wingbeat rates. During the discrimination trials, R. rouxi, H. lankadiva and E. fuscus emitted long-CF/FM, short-CF/FM and FM echolocation sounds respectively. R. rouxi, H. lankadiva and E. fuscus were able to discriminate a difference in wingbeat rate of 2.7 Hz, 9.2 Hz and 15.8 Hz, respectively, between two simultaneously presented targets at an absolute wingbeat rate of 60 Hz, using a criterion of 75% correct responses. The performance of the different bat species is correlated with the echolocation signal design used by each species, particularly with the presence and relative duration of a narrowband component preceding a broadband FM component. These results provide behavioral evidence supporting the hypothesis that bats that use CF/FM echolocation sounds have adaptations for the perception of insect wingbeat motion and that long-CF/FM species are more specialized for this task than short CF/FM species.