Threatened whales and dolphins recognize predatory killer whales from their alarming calls | 6/12/2018 | Staff
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Killer whales have a formidable reputation as one of the ocean's most ferocious predators. Hunting stealthily in packs, some populations pursue ocean-going mammals, however, other killer whales prefer to dine on a diet of fish alone, posing little or no threat to the mammals that share their waters. Knowing that some species, including birds and mammals, are capable of assessing the risk that they are under from predators in the vicinity, Matthew Bowers from Duke University and colleagues wondered whether aquatic mammals that are known to reside alongside killer whales and feature on their menu could distinguish the calls of the predatory killers from those of other marine mammals. With his Ph.D. supervisors, Douglas Nowacek and Andrew Read from Duke University, USA, and Ari Friedlander (University of California at Santa Cruz, USA), Vincent Janik (University of St Andrews, UK) and Brandon Southall (Southall Environmental Associates, USA), Bowers decided to investigate how pilot whales and Risso's dolphins react to the calls of killer whales. They publish their discovery that a subset of orca calls—with many of the characteristics that are found in human screams—trigger whales and dolphins to flea, while other less threatening calls do not provoke cetaceans to take evasive action, in Journal of Experimental Biology.

Sailing 40 miles off the North Carolina coast to monitor pods of pilot whales and to Catalina Island off the coast of California to observe small groups of Risso's dolphins, Bowers and his colleagues prepared to play recordings of killer whales and social calls from pilot whales, Risso's dolphins and humpback whales to the animals while observing their reactions. 'Each playback experiment was an all-day endeavour', says Bowers, who describes tagging one member from each group with a data-logger that recorded the sounds heard by the animals, in addition to their depth and movements. Then,...
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