Bats are unusually insensitive to brief low-frequency tones
Bats use brief calls for echolocation, suggesting that they might be more sensitive to brief sounds than non-echolocating mammals. To investigate this possibility, absolute thresholds for brief tones were determined for four species of bats: The Common vampire bat (Desmodus rotundus) and the Greater spear-nosed bat (Phyllostomus hastatus), both of which use frequency-modulated calls, the Egyptian fruit bat (Rousettus aegyptiacus), an echolocator that uses tongue-clicks rather than laryngeal calls, and the Dog-faced fruit bat (Cynopterus brachyotis), a non-echolocating species. Norway rats and a human were tested for comparison using the same acoustic stimuli. Contrary to expectations, the echolocating bats were not superior to non-echolocating mammals in detecting brief tones in the frequency range of their echolocation calls. Instead, all four species of bats were remarkably less sensitive than non-bats to brief sounds of 10 kHz and below. This implies that temporal summation in the mammalian auditory system can show large species differences, and that the detection of brief sound is likely influenced by the selective pressures on each species as well as by the physical integration of energy in the auditory system. Such species differences in function are expected to be reflected in the physiology of their auditory systems.
KeywordsTemporal summation/integration Bats Rats Humans
Supported by National Institutes of Health Grants R01-DC02960 and R15-DC009321. We thank Dr. Greg Meyer for his help in understanding the details of partial regression procedures in SPSS. We thank the Smithsonian's National Zoo, the Lubee Bat Conservancy, and the Milwaukee County Zoo for the loan of bats.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no competing interests.
Human and animal rights
All animals were cared for following the Guide for the Care and Use of Animals. All procedures were conducted with the approval of the institutional committees overseeing research with humans and with animal subjects, and were in accord with the ethical standards of the institutional research committee and with the 1964 Helsinki declaration and its later amendments.
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