TY - JOUR
T1 - Whistling is metabolically cheap for communicating bottlenose dolphins (Tursiops truncatus)
AU - Pedersen, Michael B.
AU - Fahlman, Andreas
AU - Borque-Espinosa, Alicia
AU - Madsen, Peter T.
AU - Jensen, Frants H.
N1 - Funding Information:
M.P.B. received financial support from a Company of Biologists JEB travel fellowship JEBTF181150, and a grant from the Danish Acoustical Society. F.H.J. was supported by an AIAS-COFUND fellowship from Aarhus Institute of Advanced Studies under the FP7 program of the EU (agreement no. 609033). P.T.M. and recording equipment were funded by a large frame grant from Danish Council for Independent Research | Natural Sciences (Natur og Univers, Det Frie Forskningsråd). A.F. was supported by Fundación Oceanogrà de la Comunitat Valenciana and Global Diving Research.
Publisher Copyright:
© 2020. Published by The Company of Biologists Ltd.
PY - 2020
Y1 - 2020
N2 - Toothed whales depend on sound for communication and foraging, making them potentially vulnerable to acoustic masking from increasing anthropogenic noise. Masking effects may be ameliorated by higher amplitudes or rates of calling, but such acoustic compensation mechanisms may incur energetic costs if sound production is expensive. The costs of whistling in bottlenose dolphins (Tursiops truncatus) have been reported to be much higher (20% of resting metabolic rate, RMR) than theoretical predictions (0.5–1% of RMR). Here, we address this dichotomy by measuring the change in the resting O2 consumption rate (V O2), a proxy for RMR, in three post-absorptive bottlenose dolphins during whistling and silent trials, concurrent with simultaneous measurement of acoustic output using a calibrated hydrophone array. The experimental protocol consisted of a 2-min baseline period to establish RMR, followed by a 2-min voluntary resting surface apnea, with or without whistling as cued by the trainers, and then a 5-min resting period to measure recovery costs. Daily fluctuations in V O2 were accounted for by subtracting the baseline RMR from the recovery costs to estimate the cost of apnea with and without whistles relative to RMR. Analysis of 52 sessions containing 1162 whistles showed that whistling did not increase metabolic cost (P>0.1, +4.2±6.9%) as compared with control trials (−0.5±5.9%; means±s.e.m.). Thus, we reject the hypothesis that whistling is costly for bottlenose dolphins, and conclude that vocal adjustments such as the Lombard response to noise do not represent large direct energetic costs for communicating toothed whales.
AB - Toothed whales depend on sound for communication and foraging, making them potentially vulnerable to acoustic masking from increasing anthropogenic noise. Masking effects may be ameliorated by higher amplitudes or rates of calling, but such acoustic compensation mechanisms may incur energetic costs if sound production is expensive. The costs of whistling in bottlenose dolphins (Tursiops truncatus) have been reported to be much higher (20% of resting metabolic rate, RMR) than theoretical predictions (0.5–1% of RMR). Here, we address this dichotomy by measuring the change in the resting O2 consumption rate (V O2), a proxy for RMR, in three post-absorptive bottlenose dolphins during whistling and silent trials, concurrent with simultaneous measurement of acoustic output using a calibrated hydrophone array. The experimental protocol consisted of a 2-min baseline period to establish RMR, followed by a 2-min voluntary resting surface apnea, with or without whistling as cued by the trainers, and then a 5-min resting period to measure recovery costs. Daily fluctuations in V O2 were accounted for by subtracting the baseline RMR from the recovery costs to estimate the cost of apnea with and without whistles relative to RMR. Analysis of 52 sessions containing 1162 whistles showed that whistling did not increase metabolic cost (P>0.1, +4.2±6.9%) as compared with control trials (−0.5±5.9%; means±s.e.m.). Thus, we reject the hypothesis that whistling is costly for bottlenose dolphins, and conclude that vocal adjustments such as the Lombard response to noise do not represent large direct energetic costs for communicating toothed whales.
KW - Acoustic communication
KW - Respiratory physiology
KW - Sound production
KW - Toothed whales
KW - Underwater noise
KW - Vocal modifications
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U2 - 10.1242/jeb.212498
DO - 10.1242/jeb.212498
M3 - Article
C2 - 31796610
AN - SCOPUS:85077093484
SN - 0022-0949
VL - 223
JO - Journal of Experimental Biology
JF - Journal of Experimental Biology
IS - 1
M1 - jeb212498
ER -