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Dolphin "Chef" Follows Cuttlefish Recipe

Christine Dell'Amore
National Geographic News
January 28, 2009
 
A wild dolphin has been observed following a specific recipe for preparing a mollusk meal, even stripping the animal of its internal shell and beating it free of ink, a new study says.

The female Indo-Pacific bottlenose dolphin was seen repeatedly catching, killing, and preparing giant cuttlefish, which are relatives of octopuses and squid.

The creatures spawn in huge numbers in South Australia's Upper Spencer Gulf. (See a map of southern Australia.)

"It's an example of quite sophisticated behavior," said study co-author Tom Tregenza, a research fellow at the University of Exeter.

Despite their lack of limbs, dolphins have developed clever ways to use their snouts, Tregenza noted.

"A dolphin is like a genius trapped in the body of a fish."

(Related: "Dolphins Name Themselves With Whistles, Study Says" [May 8, 2006].)

Meal Prep

In 2003 and 2007, the same dolphin (identified by the circular scars on its head) was filmed underwater prepping its meal by researchers Mark Norman and Julian Finn of Museum Victoria in Melbourne, Australia.

The female herded a cuttlefish to the seafloor, pinned it with her snout, and thrusted downward, breaking the cuttlefish's internal shell, or cuttlebone, and instantly killing it.

The dolphin then raised the dead body into the water and beat it with her snout, draining its ink.

Next the prey was returned to the seafloor, where the dolphin scraped it along the sand to strip off its bone.

Ink is difficult to digest and is generally unpleasant to the dolphin, Tregenza said, and the bone is not nutritious.

Such a complex series of behaviors are unusual among mammals, especially marine mammals, said Tregenza, whose research appeared January 21 in the journal PLoS One.

The skills are particularly advanced, he added, because the reward only comes at the end—the dolphin did not get a treat at the end of each step as it would have were it trained.

Learned Behavior?

The study team observed behaviors of dolphin pods above-water in the Australian gulf that suggest such culinary prowess is widespread among that population.

For example, the team found intact, clean cuttlebones at the ocean's surface when pods of dolphins passed through.

Now, a "fascinating" question is whether the behaviors are learned, Tregenza said.

If the behavior is passed on, as is seen with sponge-tool use in Shark Bay, Australia, for instance, this gives the animal "an amazing amount of flexibility," Tregenza said.

Learned behavior "can bring the power of multiple generations to bear on a particular problem," he said, as opposed to a single individual inventing the process from scratch in its lifetime.

Stefanie Gazda, a dolphin researcher at the University of Massachusetts Dartmouth, researches how dolphins divide labor in Cedar Key, Florida.

The finding that several members of the Australian dolphin pod seem to be cuttlefish chefs "lends credence to the idea that the behavior is learned," Gazda said in an email. She has received funding from the National Geographic Society, which owns National Geographic News.

"This interesting behavior adds to the literature on the extensive variations on foraging strategies found in bottlenose dolphins," she added.
 

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