ABSTRACT
Fundamental scaling relationships influence the physiology of vital rates, which in turn shape the ecology and evolution of organisms. For diving mammals, benefits conferred by large body size include reduced transport costs and enhanced breath-holding capacity, thereby increasing overall foraging efficiency. Rorqual whales feed by engulfing a large mass of prey-laden water at high speed and filtering it through baleen plates. However, as engulfment capacity increases with body length (engulfment volume∝body length3.57), the surface area of the baleen filter does not increase proportionally (baleen area∝body length1.82), and thus the filtration time of larger rorquals predictably increases as the baleen surface area must filter a disproportionally large amount of water. We predicted that filtration time should scale with body length to the power of 1.75 (filter time∝body length1.75). We tested this hypothesis on four rorqual species using multi-sensor tags with corresponding unoccupied aircraft systems-based body length estimates. We found that filter time scales with body length to the power of 1.79 (95% CI: 1.61–1.97). This result highlights a scale-dependent trade-off between engulfment capacity and baleen area that creates a biomechanical constraint to foraging through increased filtration time. Consequently, larger whales must target high-density prey patches commensurate to the gulp size to meet their increased energetic demands. If these optimal patches are absent, larger rorquals may experience reduced foraging efficiency compared with smaller whales if they do not match their engulfment capacity to the size of targeted prey aggregations.
Footnotes
Competing interests
The authors declare no competing or financial interests.
Author contributions
Conceptualization: S.R.K., M.S.S., D.E.C., J.A.G.; Methodology: S.R.K., M.S.S., D.E.C., K.C.B.; Software: D.E.C., K.C.B., J.A.F.; Validation: S.R.K., M.S.S., D.E.C., P.S.S.; Formal analysis: S.R.K., M.S.S., D.E.C., P.S.S., K.C.B., J.D., J.A.F.; Investigation: S.R.K., M.S.S., D.E.C., P.S.S., K.C.B., J.A.C., J.D., J.A.F., A.S.F., D.W.J., A.J.W., J.A.G.; Resources: K.C.B., J.A.C., J.D., D.W.J., A.J.W., J.A.G.; Data curation: S.R.K., M.S.S., D.E.C., P.S.S., K.C.B., J.D., J.A.F., A.J.W.; Writing - original draft: S.R.K., J.A.G.; Writing - review & editing: S.R.K., M.S.S., D.E.C., P.S.S., K.C.B., J.D., J.A.F., A.S.F., D.W.J., A.J.W., J.A.G.; Visualization: S.R.K., M.S.S.; Supervision: J.A.C., A.S.F., D.W.J., J.A.G.; Project administration: J.A.C., A.S.F., D.W.J., J.A.G.; Funding acquisition: J.A.C., A.S.F., D.W.J., J.A.G.
Funding
This research was funded in part by grants from the National Science Foundation (IOS-1656691, IOS-1656676, IOS-1656656, OPP-1644209) and the Office of Naval Research (N000141612477), and a Terman Fellowship from Stanford University. Additional Monterey Bay CATS tag deployments were funded by grants from the American Cetacean Society Monterey and San Francisco Bay chapters, and by the Drs Earl H. Myers and Ethel M. Myers Oceanographic and Marine Biology Trust.
Data availability
The datasets supporting this article are available at Kahane-Rapport et al. (2020): dryad.n5tb2rbt2.
Supplementary information
Supplementary information available online at https://jeb.biologists.org/lookup/doi/10.1242/jeb.224196.supplemental
- Received February 26, 2020.
- Accepted August 13, 2020.
- © 2020. Published by The Company of Biologists Ltd
Log in using your username and password
Log in through your institution
Pay Per Article - You may access this article (from the computer you are currently using) for 1 day for US$30.00 .
Regain Access - You can regain access to a recent Pay per Article purchase if your access period has not yet expired.