They could be talking about you . . . Prairie dogs tailor alarm calls to individuals, researcher finds

September 28, 1991|By Douglas Birch

Next time you pass the prairie dog exhibit at the zoo, listen carefully to their chatter. They could be talking about you.

A zoologist who has studied two colonies of the Gunnison's species of prairie dog in Arizona said he has discovered that the animals use a vocabulary of alarm calls so rich they can describe individual predators. If this is correct, other scientists say, the Gunnison's calls would be one of the most complex animal languages ever studied in the wild.

Dr. Constantine N. "Con" Slobodchikoff of Northern Arizona University said Gunnison's prairie dogs give different alarm calls for humans, owls, hawks, domestic dogs, ferrets and coyotes. Furthermore, he said, the animal can identify individual humans, dogs and coyotes in terms of their size, shape and color.

That means, he said, that when a Gunnison's sees a person and gives an alarm, it doesn't simply say, "Predator!" It actually says, for example, "Tall dark thin man!"

"It's a very sophisticated, abstract communication system that seems to have some of the elements that human language has," said Dr. Slobodchikoff, who is publishing part of his research in a forthcoming edition of the British journal Animal Behaviour.

The distinction between predators may be important, he said, because the animals react differently to different threats.

When a hawk or owl appears, prairie dogs will dive into their burrows and stay out of sight, he said. With an approaching coyote, they will run to the lip of their burrow and keep watch. With a domestic dog, the Gunnison's will merely stand up and track the predator. But with humans, they will scurry into their burrows, then pop their heads back out to watch.

The 47-year-old researcher says the Gunnison's ability t distinguish between individual predators may help them avoid older, more experienced enemies. And it may help them anticipate the movements and tactics of predators who regularly raid the colony.

Several other zoologists said the reports so far about Dr. Slobodchikoff's work are exciting, but they want to see the details of his research before passing judgment.

"It's fantastic," said John L. Hoogland, zoologist with the University of Maryland's Appalachian Environmental Laboratory in Frostburg and an authority on prairie dog behavior. "But at this point, it is preliminary. We want to know what it means."

Paul W. Sherman, professor of animal behavior at Cornell University, said he had not reviewed the research but called the possibility that prairie dogs can give detailed descriptions of predators "absolutely fascinating."

"The kind of discrimination you're describing has hitherto only been known in primates," he said.

Dr. Slobodchikoff noted that researchers have found that vervet monkeys in Africa have specific calls for four predators: pythons, eagles, baboons and leopards. Chickens and two species of ground squirrel have one call for aerial predators, another for those approaching on the ground. (Other scientists have tried to teach human-designed languages to primates and marine mammals, such as dolphins.)

But the level of sophistication that we're finding in terms of description of individual predators, as far as I know, no one has shown that in any other species of animal -- except humans, of course," he said.

He said his team has compiled a list of six Gunnison's calls, each for a specific predator. By slightly altering those calls, he said, the animals add "shades of meaning" making them "the equivalent of sentences."

During the study, his student assistants learned to distinguish between the call for one predator and that for another. (The Gunnison's basic call for a human, he said, sounds like the rasping chirp of a small bird.)

"The students would hear the vocalization for coyote and look around for the coyote that elicited it," he said. "And sure enough, there's the coyote."

The article in Animal Behaviour focuses on the prairie dogs' reactions to humans, for centuries one of the animals' major predators.

The researchers conducted a series of experiments in which they sent students of various sizes and shapes walking through the colony in different dress. Then they used the computer to analyze the calls each student triggered, to determine how the calls were structurally similar and how they were different.

By this method, Dr. Slobodchikoff said, researchers were able to identify that part of the call that referred to a given color, height or shape.

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