Effect of acoustic clutter on prey detection by bats

Bats that capture animal prey from substrates often emit characteristic ech olocation calls that are short-duration, frequency-modulated (FM) and broad band(1). Such calls seem to be suited to locating prey in uncluttered habit ats, including flying prey, but may be less effective for finding prey amon g cluttered backgrounds because echoes reflecting from the substrate mask t he acoustic signature of prey(2-4). Perhaps these call designs serve primar ily for spatial orientation(5-7). Furthermore, it has been unclear whether the acoustic image conveyed by FM echoes enables fine texture discriminatio n(3,8,9), or whether gleaning bats that forage in echo-cluttering environme nts must locate prey by using other cues, such as prey-generated sounds(5-7 ,10-13). Here we show that two species of insectivorous gleaning bats perfo rm badly when compelled to detect silent and immobile prey in clutter, but are very efficient at capturing noisy prey items among highly cluttered bac kgrounds, and both dead or live prey in uncluttered habitats. These finding s suggest that the short, broadband FM echolocation calls associated with g leaning bats are not adapted to detecting prey in clutter.