Risso's dolphins perform spin dives to target deep-dwelling prey

Royal Society Open Science, vol. 8, pp. 202320

Abstract

Foraging decisions of deep-diving cetaceans can provide fundamental insight into food web dynamics of the deep pelagic ocean. Cetacean optimal foraging entails a tight balance between oxygen-conserving dive strategies and access to deep-dwelling prey of sufficient energetic reward. Risso's dolphins (Grampus griseus) displayed a thus far unknown dive strategy, which we termed the spin dive. Dives started with intense stroking and right-sided lateral rotation. This remarkable behaviour resulted in a rapid descent. By tracking the fine-scale foraging behaviour of seven tagged individuals, matched with prey layer recordings, we tested the hypothesis that spin dives are foraging dives targeting deep-dwelling prey. Hunting depth traced the diel movement of the deep scattering layer, a dense aggregation of prey, that resides deep during the day and near-surface at night. Individuals shifted their foraging strategy from deep spin dives to shallow non-spin dives around dusk. Spin dives were significantly faster, steeper and deeper than non-spin dives, effectively minimizing transit time to bountiful mesopelagic prey, and were focused on periods when the migratory prey might be easier to catch. Hence, whereas Risso's dolphins were mostly shallow, nocturnal foragers, their spin dives enabled extended and rewarding diurnal foraging on deep-dwelling prey.

Authors 7

1. Fleur Visser corresponding

   Royal Netherlands Institute for Sea Research · University of Amsterdam

   Affiliation as printed

   Department of Coastal Systems, NIOZ Royal Netherlands Institute for Sea Research, PO Box 59, 1790 AB, Den Burg, Texel, The Netherlands

   Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, PO Box 94240, 1090 GE, Amsterdam, The Netherlands

   Kelp Marine Research, 1624 CJ, Hoorn, The Netherlands

2. Onno A. Keller

   Utrecht University · Royal Netherlands Institute for Sea Research · University of Amsterdam

   Affiliation as printed

   Department of Biology, Utrecht University, 3584 CH, Utrecht, The Netherlands

   Department of Coastal Systems, NIOZ Royal Netherlands Institute for Sea Research, PO Box 59, 1790 AB, Den Burg, Texel, The Netherlands

   Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, PO Box 94240, 1090 GE, Amsterdam, The Netherlands

3. Machiel G. Oudejans
   Affiliation as printed

   Kelp Marine Research, 1624 CJ, Hoorn, The Netherlands

4. Douglas P. Nowacek

   Duke University

   Affiliation as printed

   Nicholas School of the Environment, Duke University Marine Laboratory, Beaufort, NC 28516, USA

   Pratt School of Engineering, Duke University, Durham, NC 27708, USA

5. Annebelle C. M. Kok Aachen Institute of Biology, Leiden University

   Leiden University · Scripps Institution of Oceanography

   Affiliation as printed

   Institute of Biology, Leiden University, PO Box 9509, 2300 RA, Leiden, The Netherlands

   Kelp Marine Research, 1624 CJ, Hoorn, The Netherlands

   Scripps Institution of Oceanography, UCSD, La Jolla 92093–0205, USA

6. Jef Huisman

   University of Amsterdam

   Affiliation as printed

   Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, PO Box 94240, 1090 GE, Amsterdam, The Netherlands

7. Elisabeth H. M. Sterck

   Utrecht University · Biomedical Primate Research Centre

   Affiliation as printed

   Animal Science Department, Biomedical Primate Research Centre, 2288 GJ, Rijswijk, The Netherlands

   Department of Biology, Utrecht University, 3584 CH, Utrecht, The Netherlands