Echolocating bats emit trains of intense ultrasonic biosonar pulses and listen to weaker echoes returning from objects in their environment. Identification and categorization of echoes are crucial for orientation and prey capture. Bats are social animals and often fly in groups in which they are exposed to their own emissions and to those from other bats, as well as to echoes from multiple surrounding objects. Sound pressure levels in these noisy conditions can exceed 110 dB, with no obvious deleterious effects on echolocation performance. Psychophysical experiments show that big brown bats (Eptesicus fuscus) do not experience temporary threshold shifts after exposure to intense broadband ultrasonic noise, but it is not known if they make fine-scale adjustments in their pulse emissions to compensate for any effects of the noise. We investigated whether big brown bats adapt the number, temporal patterning or relative amplitude of their emitted pulses while flying through an acoustically cluttered corridor after exposure to intense broadband noise (frequency range 10–100 kHz; sound exposure level 152 dB). Under these conditions, four bats made no significant changes in navigation errors or in pulse number, timing and amplitude 20 min, 24 h or 48 h after noise exposure. These data suggest that big brown bats remain able to perform difficult echolocation tasks after exposure to ecologically realistic levels of broadband noise.
The authors declare no competing or financial interests.
K.N.H., J.A.S. and A.M.S. designed research; K.N.H. and M.L. conducted research; K.N.H., M.L. and J.A.S. analyzed data; A.M.S. and K.N.H. wrote the manuscript.
This research was supported by grants from the Capita Foundation, Brown University and the Office of Naval Research (Grant N00014-14-1-05880) to J.A.S. M.L. was funded by an individual postdoctoral fellowship from the Deutscher Akademischer Austauschdienst.
The data from this study are publicly available at the Brown Data Repository https://doi.org/10.7301/Z0BP00QG.
Supplementary information available online at http://jeb.biologists.org/lookup/doi/10.1242/jeb.143578.supplemental
- Received May 23, 2016.
- Accepted August 4, 2016.
- © 2016. Published by The Company of Biologists Ltd