Unravelling the calls of discrete hunters: acoustic structure of echolocation calls of furipterid bats (Chiroptera, Furipteridae)

Detailed descriptions of echolocation calls for most of the Neotropical bat species have been published only recently. Yet, the available descriptions are from bats that emit high-intensity calls. The families of insectivorous bats that emit low-intensity calls, such as Furipteridae, are less frequently recorded by more traditional equipment; thus, there are no detailed descriptions of echolocation calls for these species. The family Furipteridae includes only two species of small insectivorous bats from Neotropics, the thumbless bat Furipterus horrens and the smoky bat Amorphochilus schnablii. The ecology, behaviour and even the natural history of both species are barely known. In order to contribute to the description of echolocation calls of Neotropical bat species and to the knowledge of these two poorly known species, here we describe in more detail the echolocation calls of furipterids. Thumbless bats were recorded from two colonies, one located in south-western Bahia, Brazil, and another located in the Amazon forest of Matoury, French Guyana, whereas the smoky bats were recorded in the Pacific coast of Arequipa, south-western Peru. Echolocation calls of both species were characterized by pulses of downward broadband frequency-modulated sweeps of short duration. Our results show that the ultrasound calls emitted by thumbless bats is one of the highest in frequency among Neotropical bats. This detailed characterization of furipterid calls and their distinct features, like very high frequencies and wide bandwidth, making it relatively easy to identify, aids in the inclusion of these species in acoustic surveys and monitoring.