Killer whales, new research

This video is called BBC Natural World: The Woman Who Swims With Killer Whales.

From Wildlife Extra:

Killer whales found to eavesdrop on prey

December 2013: UK Scientists have found evidence that marine-mammal-eating killer whales rely on acoustic clues to locate their prey.

While biologists had evidence that the whales do not echolocate while hunting, due to the excellent hearing of the seals, porpoises and other animals the whales hunt, they were still unsure exactly how the animals do find their prey in the murky northern waters off the west coast of North America.

However, a two-year study by Volker Deecke, a researcher at the Centre for Wildlife Conservation at the University of Cumbria, UK has revealed that killer whales can successfully locate prey even in near-complete darkness. Deecke notes that this new evidence of night-time hunting rules out visual cues as the only means of prey detection.

“We now suspect that mammal-eating killer whales are primarily eavesdropping on sounds generated by their prey to find food,” he said.

Deecke and his colleagues traveled to Alaska to conduct the study, analysing huge quantities of data gathered from acoustic recording tags placed on 13 killer whales. The tags, which are about the size of a cell phone, were attached to the whales with four suction cups and could stay on for up to 16 hours.

The tags’ accelerometers, compass, depth sensor, and hydrophone recorded data on the animals’ movements and any sounds it heard or made. Deecke and his colleagues were able to identify predation events by the characteristic sound of a whale dispatching its prey with a hit from its tail fluke.

Deecke said of one unfortunate seal’s demise: “As soon as we put one of the tags on, it started to record seal roars, which are part of the display that male harbor seals use to attract females. Over the next half hour the roars got louder and louder, then there are a sequence of three quite loud roars that suggest the seal is within a few hundred meters of the killer whale. Twenty-seven seconds later there are the sounds of a predation event, and then no more roars.”

Deecke notes that such a story is compelling but does not provide direct evidence that killer whales are tuning in to the sounds of their prey. Going forward, he hopes to use playback experiments to test killer whales’ responses to recorded seal roars and porpoise echolocation clicks.

Related articles

• Killer whales go into silent stealth mode to stalk mammals (nbcnews.com)
• Stealth Mode: Killer Whales Go Dark to Stalk Prey (livescience.com)
• Sea lions looking for love may end up lunch for killer whales: study (ctvnews.ca)
• Silent stalkers of dark ocean waters (eurekalert.org)
• Keen hearing helps transient killer whales hunt prey (theglobeandmail.com)
• Killer Whale Might be Released off Iceland’s Shores (icelandreview.com)

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