Foraging rates of ram‐filtering North Atlantic right whales

van der Hoop, J.M., Nousek-McGregor, A.E. , Nowacek, D.P., Parks, S.E., Tyack, P. and Madsen, P.T. (2019) Foraging rates of ram‐filtering North Atlantic right whales. Functional Ecology, 33(7), pp. 1290-1306. (doi: 10.1111/1365-2435.13357)

186935.pdf - Accepted Version



North Atlantic right whales spend their summer months foraging primarily in American and Canadian Atlantic waters on high‐energy‐density prey. Here they rapidly accumulate and store energy obtained within a few months to support future migrations and reproduction while fasting. High drag from their ram‐filter foraging strategy places a limit on what prey densities will be energetically efficient to target. Our understanding of the volume of prey‐laden water filtered by right whales during a dive or foraging bout, and what information they use to decide to forage or not, has been limited by the difficulties of measuring when they feed at depth, how fast they swim during continuous ram filtration, and how often they might swallow accumulated prey. We used 10 DTAG deployments from right whales in the Bay of Fundy, Canada, to quantify swimming speeds and estimate the volume of prey‐laden water filtered per dive. We used the tag's inertial sensors to evaluate the timing of frequent biomechanical changes that indicate the truncation of continuous filtration, and whether the number or timing of these fluking bouts relate to longer feeding dives or other foraging decisions. During foraging dives, right whales descended at 1.4 (±0.2) m/s and slowed to swim at 1.1 (±0.3) m/s while filtering. We found consistent pauses in the fluking behaviour of foraging right whales, every 56 (±22 SD) seconds. Whales filtered on average 78 (±30) m3 of water per fluking bout, and on average filtered 673 (±201) m3 per dive. Right whales filter large volumes of water at low speeds with a high duty cycle, but require sufficiently high prey energy densities to compensate for a high‐drag foraging strategy. Closely related bowhead whales have a larger gape but swim more slowly, filtering greater volumes with lower drag. Our findings highlight that these endangered balaenids acquire their energy in a relatively short period of intense foraging; even moderate changes in their feeding behaviour or their prey energy density are likely to negatively impact their yearly energy budgets and therefore reduce fitness substantially.

Item Type:Articles
Additional Information:Funding for the tag deployments was provided by the Office of Naval Research N000140410709 and the NOAA Fisheries’ North Atlantic Right Whale Grant Program NA04NMF4720405. Tag data were collected in the U.S. and Canada under NMFS permit #14791. JVDH received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Individual Fellowship grant agreement No 706867. PLT acknowledges the support of the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) in the completion of this study. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions.
Glasgow Author(s) Enlighten ID:Mcgregor, Dr Anna
Authors: van der Hoop, J.M., Nousek-McGregor, A.E., Nowacek, D.P., Parks, S.E., Tyack, P., and Madsen, P.T.
College/School:College of Medical Veterinary and Life Sciences > School of Life Sciences
Journal Name:Functional Ecology
ISSN (Online):1365-2435
Published Online:11 May 2019
Copyright Holders:Copyright © 2019 The Authors and British Ecological Society
First Published:First published in Functional Ecology 33(7):1290-1306
Publisher Policy:Reproduced in accordance with the publisher copyright policy
Data DOI:10.5281/zenodo.2660074

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