February 23, 2010
Sperm Whales Team Up To Corral Squid
A new study suggests that sperm whales may team up and work cooperatively to hunt down and corral their food.
Scientists from the U.S. used high-tech GPS tags to study the marine mammals' astonishing hunting behaviors. The tracking equipment showed how the animals traveled together in groups, but when it came time to hunt for food, each whale took on various roles within the group.
The study, led by Professor Bruce Mate from the Hatfield Marine Science Center in Oregon, used new equipment to tag and follow the giant sea creatures. "We have [a tag with] GPS precision for the whales' movements and a time and depth record of their dives," Mate told BBC News. "And, for the first time, we have tagged several animals within the same group."
Evidence showed that the whales stayed close together over several months in and around the Gulf of Mexico. But when the animals made their dives to hunt for food their behavior varied with each dive.
Pointing to the evidence, Professor Mate said: "We can see that they're actually changing their role over time." The team speculated that when they dive, often as deep as 3,300 feet, they are hunting and "herding a ball of squid."
Mate said that some whales seemed to be guarding the bottom of the "bait ball", keeping the prey from escaping downward, while other animals in the group concentrated on the center of the ball itself. It seemed that the whales took turns diving to the physiologically demanding depths, he added.
Professor Hal Whitehead, a researcher from Dalhousie University in Nova Scotia, told BBC News he was impressed by the data, but disagreed with the suggestion that they were herding squid, saying it seemed a little "far-fetched".
However, Dr. Mate pointed to evidence from a previous research that showed that dolphins took on similar types of behavior. In that study, scientists captured footage of the dolphins herding a ball of fish, and they appeared to take turns diving through the ball taking in a mouthful of fish.
With the whales, it was difficult to capture their behavior, because they dive to far greater depths than dolphins, explained Mate.
"Our next step will be to image the squid at the same time as tracking the whales," he said. The team also plans to tag more members of the same group to gain an even better understanding of how the social creatures collaborate.
The findings of the study was announced by Professor Mate and his colleagues at the Ocean Sciences meeting in Portland, Oregon.
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