Echolocation: Implications for Ecology and Evolution of Bats

Echolocation is polyphyletic among vertebrates and is currently known from some species in the orders Caprimulgiformes, Apodiformes, Chiroptera, Cetacea, Pinnipedia, Rodentia, and Primates. The ability to echolocate permits an animal to find roosts, food, or both, irrespective of light conditions. Microchiropterans are unique in producing echolocation calls that show structured changes in frequency over time; other echolocators rely on broadband clicks. The Microchiroptera are often treated as models for echolocation, since many of them use it to detect flying prey. Nevertheless, certain other species of Microchiroptera do not use echolocation when hunting, but depend in that activity upon vision, sounds emanating from the prey, or olfaction. Some bats capable of echolocation actually cease producing echolocation calls during their attacks on prey, although others do not, even when relying on different cues to find their targets. All Microchiroptera are not obligate echolocators. Playback experiments have demonstrated that echolocation calls serve a communication role in some species of bats. Furthermore, echolocation calls appear to be derived from communication signals, and the early echolocators may have used this mode of orientation to assess background rather than to choose targets, a role still played by the echolocation of birds and shrews. Echolocation divulges a great deal of information about the echolocator itself, and so permits intraspecific and interspecific piracy of information, a consequence that could be inconvenient or fatal. Echolocation has important implications for many aspects of the behavior and ecology of animals that use it.