Local acoustic habitat relative to hearing sensitivities in beluga whales (Delphinapterus leucas)
1 Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
2 Joint Institute for the Study of the Atmosphere and Ocean ( JISAO), University of Washington, 3737 Brooklyn Avenue NE, Seattle, WA 98105, USA
3 Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, Seattle, WA 98115, USA
4 Alaska Department of Fish and Game, 1300 College Road, Fairbanks, AK 99701, USA
5 Georgia Aquarium, 225 Baker St NW, Atlanta, GA 30313, USA
6 Alaska SeaLife Center, 301 Railway Ave, Seward, AK 99664, USA
* Author to whom correspondence should be addressed.
Received: 1 Nov 2017 / Accepted: 30 Apr 2018 / Published: 20 Jun 2018
Abstract
Background noise can have a substantial effect on communication signals, however far less is known about how natural soundscapes may influence hearing sensitivity. Here we compare the audiograms of 26 wild beluga whales measured in their natural environment to a series of ecoacoustic measurements within a primary portion of their Bristol Bay summer habitat, the Nushagak Estuary in Bristol Bay, AK, USA. Environmental acoustic measurements were made during 2012 and 2016 using two different methods: a moored recorder and drifter buoys. Environmental noise curves varied substantially. Drifter recordings from the middle of Nushgak Estuary had the highest spectrum levels during ebb tides with acoustic energy from sediment transport extending well into higher frequencies (ca. 60 kHz), likely due to rapidly moving tidal flow and shifting sediment in that location. Drifter recordings near the estuary mouth and shallow tidal flats were lower amplitude. Noise levels generally varied during drifts (in one case up to ca. 6 dB) reflecting acoustic cues available to the local belugas. The moored recorder showed a substantially different spectral profile, especially at lower frequencies, perhaps due to its attachment to a pier piling and subsequent pier noise. Hearing sensitivity varied by individual and thresholds often fell above 1/3 octave-band noise levels, but not overall noise spectral density. Audiograms of the most sensitive animals closely paralleled the lowest ambient noise power spectral density curves, suggesting that an animal’s auditory dynamic range may extend to include its habitat’s quietest conditions. These data suggest a cautious approach is necessary when estimating the sound-sensitivity of odontocetes found in quiet environments as they may have sensitive auditory abilities that allow for hearing within the lowest noise-level conditions. Further, lower level ambient noise conditions could provide a conservative estimate of the maximal sensitivity of some cetacean populations within specific environments.
Keywords: noise; soundscape; cetacean; odontocete; arctic
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CITE
Mooney, T.A.; Castellote, M.; Jones, I.T.; Quakenbush, L.; Hobbs, R.; Gaglione, E.; Goertz, C. Local acoustic habitat relative to hearing sensitivities in beluga whales (Delphinapterus leucas). JEA 2018, 2, 11.
Mooney TA, Castellote M, Jones IT, Quakenbush L, Hobbs R, Gaglione E, Goertz C. Local acoustic habitat relative to hearing sensitivities in beluga whales (Delphinapterus leucas). Journal of Ecoacoustics. 2018; 2(2):11.
Mooney, T. Aran; Castellote, Manuel; Jones, Ian T.; Quakenbush, Lori; Hobbs, Roderick; Gaglione, Eric; Goertz, Caroline. 2018. "Local acoustic habitat relative to hearing sensitivities in beluga whales (Delphinapterus leucas)." JEA 2, no. 2: 11.
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