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Pilot Whales Are "Cheetahs of the Sea," Study Finds

Matt Kaplan
for National Geographic News
May 16, 2008
 
Short-finned pilot whales off the Canary Islands race like cheetahs after prey over long distances in the deep Atlantic waters, new research reveals.

Like all whales, pilot whales need to come to the surface to breathe, but they can hold their breaths for extended periods.

Short-finned pilot whales are known to dive to more than 3,200 feet (1,000 meters), but their behavior in the deep ocean has been a mystery.

Researchers monitored the whales near Tenerife, the largest island in the Spanish-controlled archipelago (see map), by attaching tags to 23 of the animals with suction cups.

The tags recorded movement, sound, and depth for one day, after which they disconnected and floated to the surface for collection.

"We really wanted to know what whale behavior was like at depth," said study author Natacha Aguilar Soto, of the University of La Laguna in Tenerife.

"We expected deep-diving whales to maintain slow speeds to conserve oxygen so they could increase the time available to search and get their food."

Instead the team found that during most daytime dives, the whales sped up to an average of 19.2 feet (6 meters) a second, with top speeds reaching 28.8 feet (9 meters) a second just before reaching the deepest point of their dives.

The whales then were found to release a buzz with their biological sonar, as if locating something in front of them. Aguilar and colleagues believe the observations indicate that the whales were chasing after prey.

The study appears in an upcoming issue of the journal Animal Ecology.

Dive! Dive!

Swimming speeds for other breath-holding animals such as seals, deep-diving birds, and dolphins have been measured at about 6.4 feet (2 meters) a second.

Aguilar assumed the situation would be similar among short-finned pilot whales.

The whales' high-speed chases have not been observed in any other deep-diving mammals.

But the behavior is not entirely unique. On land, cheetahs invest massive amounts of energy sprinting after a single prey.

The researchers suggest that the pilot whales are exhibiting the same behavior.

The suggestion is surprising, because until now the dominant predators of the deep were thought to be those that would use the dark waters to ambush their prey, as jaguars do when pouncing from behind foliage in the jungle.

"Jungles are excellent for ambushing prey. Plains are perfect for pursuit predation," Aguilar said.

"It would seem that for whales using sonar, the deep sea is like a plain, but for other animals the dark water is like a jungle. If this is true, it is a unique combination of both environments rolled into one."

The Mysterious Fathoms Below

Patrick Miller, a marine biologist at St. Andrew's University in Scotland, was not involved in the study.

"This is an important finding that reveals a previously undescribed foraging strategy in a deep-diving whale," he said.

"I think they are on to something there about echolocation [using sonar to locate prey] turning a jungle into a savanna."

Steve Thompson, a behavioral ecologist at Chicago's Lincoln Park Zoo, was also not part of Aguilar's research team.

He said the sprinting, or "bursting," behavior observed in the pilot whales seemed significant.

"I'm guessing that these whales burst because they are specializing on [hunting] something that moves really quickly—large squid perhaps—when they get close to them," Thompson said.

"What's interesting," he said, "is that other [whale] species don't burst too, or at least they have not been detected doing so yet," he added.
 

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