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.
- Baron G, Stephan H, Frahm HD (1996) Comparative neurobiology in chiroptera. Birkhauser Verlag, BerlinGoogle Scholar
- Bellwood JJ (1986) Foraging behavior, prey selection, and echolocation in phyllostomid bats (Phyllostomidae). In: Nachtigall PE, Moore PWB (eds) Animal sonar processes and performance. Plenum Press, New York, pp 601–605Google Scholar
- Greenhall AM, Schmidt U (1988) Natural history of vampire bats. CRC Press, Boca RatonGoogle Scholar
- Heffner HE, Heffner RS (1995) Conditioned avoidance. In: Klump GM, Dooling RJ, Fay RR, Stebbins WC (eds) Methods in comparative psychoacoustics. Birkhäuser, Basel, pp 73–87Google Scholar
- Heffner HE, Koay G, Heffner RS (2006a) Behavioral assessment of hearing in mice—conditioned suppression. In: Crowley J et al (eds) Current protocols in neuroscience. Wiley, New York, pp 8.21D.1–8.21D.15Google Scholar
- Hill JE, Smith JD (1984) Bats: a natural history. University of Texas Press, AustinGoogle Scholar
- Kastelein RA, Hoek L, Terhune JM, de Jong CAF, Wensveen PJ (2010b) The effect of signal duration on the underwater detection thresholds of a harbor porpoise (Phocoena phocoena) for single frequency-modulated tonal signals between 0.25 and 160 kHz. J Acoust Soc Am 128:3211–3222CrossRefPubMedGoogle Scholar
- Pye JD (1980) Adaptiveness of echolocation signals in bats: flexibility and evolution. Trends Neurosci 10:232–235Google Scholar
- Schmidt U (1972) Social calls of juvenile vampire bats (Desmodus rotundus) and their mothers. Zool Beitr 4:310–316Google Scholar
- Siegel S (1956) Nonparametric statistics. McGraw-Hill, New YorkGoogle Scholar
- Yost WA (2007) Fundamentals of hearing. Academic Press, San DiegoGoogle Scholar