Saturday, 1 May 2010

Killer Whales and Herring: Using Sound to Get a Meal


Norwegian and Icelandic killer whales use a variety of techniques to get their dinner, many of which are acoustic. In defense, their prey employ clever acoustical countermeasures of their own. Icelandic killer whales, as we have discovered, employ an additional strategy, apparently not shared by their Norwegian cousins, that may give them an extra advantage in capturing their prey.

Killer whales of the Northeast Atlantic feed primarily on herring. In Norwegian waters billions of herring migrate from open oceanic waters into deep fjords in the late fall to over winter. Here they form vast schools that move up and down in the water column in daily rhythms “waiting” for spring to approach. In February, they migrate about 1,000 km south to their spawning grounds, and then out to open waters again. Groups of killer whales follow the herring to cooperatively feed on this favored prey. Often the whales dive to over a hundred meters to drive herring up to shallower waters forcing the fish into tight groups by swimming around them and flashing their white bellies at them.

During this process the whales emit a cacophony of sounds (echolocation clicks, click bursts, and whistles), some of which may help to tighten the herring school or coordinate whale movements. At the right moment individual whales swim into the herd of fish and perform underwater tail slaps that produce thud-like sounds and strong local water currents. Many fish turn belly-up and remain motionless, apparently stunned by the tail slap. Whales swim leisurely to the stunned fish and consume these one by one.


Lee A. Miller (lee@biology.sdu.dk), Malene Simon, Fernando Ugarte, and Magnus Walberg
Institute of Biology
University of Southern Denmark
Campusvej 55
5230 Odense M
Denmark

Popular version of paper 4aAO2 Presented Thursday Morning, June 8, 2006 151st ASA Meeting, Providence, RI