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J Exp Biol. 2018 Feb 28;221(Pt 4). pii: jeb165209. doi: 10.1242/jeb.165209.

Risso's dolphins plan foraging dives.

Author information

Sea Mammal Research Unit, School of Biology, University of St Andrews, East Sands, St Andrews KY16 8LB, UK
Department of Animal Biology, University of La Laguna, Avda. Astrofisico Fco Sanchez s/n, La Laguna 36200, Tenerife, Spain.
Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA 95039, USA.
Southall Environmental Associates, 9099 Soquel Drive, Suite 8, Aptos, CA 95003, USA.
Long Marine Laboratory, Institute of Marine Sciences, University of California Santa Cruz, 1156 High St, Santa Cruz, CA 95064, USA.
Cascadia Research Collective, 218 1/2 4th Ave W, Olympia, WA 98501, USA.
Department of Fisheries and Wildlife, Marine Mammal Institute, 2030 Marine Science Drive, Newport, OR 97365, USA.
Sea Mammal Research Unit, School of Biology, University of St Andrews, East Sands, St Andrews KY16 8LB, UK.


Humans remember the past and use that information to plan future actions. Lab experiments that test memory for the location of food show that animals have a similar capability to act in anticipation of future needs, but less work has been done on animals foraging in the wild. We hypothesized that planning abilities are critical and common in breath-hold divers who adjust each dive to forage on prey varying in quality, location and predictability within constraints of limited oxygen availability. We equipped Risso's dolphins with sound-and-motion recording tags to reveal where they focus their attention through their externally observable echolocation and how they fine tune search strategies in response to expected and observed prey distribution. The information from the dolphins was integrated with synoptic prey data obtained from echosounders on an underwater vehicle. At the start of the dives, whales adjusted their echolocation inspection ranges in ways that suggest planning to forage at a particular depth. Once entering a productive prey layer, dolphins reduced their search range comparable to the scale of patches within the layer, suggesting that they were using echolocation to select prey within the patch. On ascent, their search range increased, indicating that they decided to stop foraging within that layer and started searching for prey in shallower layers. Information about prey, learned throughout the dive, was used to plan foraging in the next dive. Our results demonstrate that planning for future dives is modulated by spatial memory derived from multi-modal prey sampling (echoic, visual and capture) during earlier dives.


Animal decision making; Episodic-like memory; Foraging behaviour; Grampus griseus; Perceptual range; Predator–prey dynamics

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