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Page last updated at 12:57 GMT, Tuesday, 2 February 2010
Burrowing US prairie dogs use complex language
By Matt Walker
Editor, Earth News

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Sound of the underground

A tiny rodent may have the most sophisticated language of any animal.

This bold claim comes from US-based academic Professor Con Slobodchikoff who has long studied the vocal repertoire of Gunnison's prairie dog.

With a single bark, he says, a prairie dog may warn about the type and direction of an encroaching predator, and even describe its colour.

If confirmed, that means the chattering rodents communicate in a more complex way than even monkeys or dolphins.

Prof Slobodchikoff details the experiments he has done to reveal the hidden structure of the prairie dog's language within the BBC natural history programme "Prairie dogs, talk of the town," broadcast as part of the Natural World documentary series.

They have words for different predators, they have descriptive words for describing the individual features of different predators
Prof Slobodchikoff

Prairie dogs belong to the squirrel family, and live in the prairies and semi-desert grassland of northern Arizona, northern New Mexico and southwest Colorado.

Once existing in their billions, prairie dog numbers have now plummeted as ranchers view them as vermin competing for resources with livestock.

But those remaining still live in huge colonies of hundreds of animals, digging complex underground burrow systems.

Whenever a predator approaches, the small rodents let out a series of barks, squeals and squeaks.

For 30 years, Prof Slobodchikoff and colleagues have been recording these calls.

To analyse them, the scientists set up a series of experiments, dragging models of different predators in front of wary prairie dogs, recording if they respond differently to coyotes, hawks and badgers.

Predatory playback

The researchers found that the prairie dogs are confronted by so many predators that they have evolved different "words" to describe them all.

These words are barks and sounds that contain different numbers of rhythmic chirps and frequency modulations.

Individual prairie dogs have different tonal qualities, just as human voices differ, but different rodents use the same words to describe the same predators, allowing the alarm call to be understood by the rest of the colony.

For example, a single bark may be attuned to say "tall, skinny coyote in distance, moving rapidly towards colony".

Other scientists have challenged this idea, because it would mean that in one short bark, prairie dogs relay information about the size, colour, direction and speed of travel of an encroaching predator.

Prof Slobodchikoff's team believes the prairie dogs include this information by varying the modulation of the call and the harmonics in the bark.

By doing so, they can pack in a vast amount of information into a very short sound.

PRAIRIE DOGS: FIND OUT MORE

"Prairie dogs have the most complex natural language that has been decoded so far. They have words for different predators, they have descriptive words for describing the individual features of different predators, so it's a pretty complex language that has a lot of elements," says Prof Slobodchikoff.

In the documentary, the scientists record for the first time the prairie dogs' call to warn about badgers.

It is subtly but consistently different to all the other calls.

When the alarm call is played back to a colony of rodents they react differently to when they are played a call warning of coyotes.

Coyotes hunt by surprise so the rodents respond by instantly bolting. Badgers try to dig into burrows, and when the prairie dogs are warned of a badger they become instantly vigilant instead.

Prof Slobodchikoff believes the prairie dogs may have evolved such complex language because they live in a complex, social society housed in a highly engineered and complex burrow system.

Not only do they live in highly organised "towns" of hundreds of individuals, but they also have to compete with squatters, such as cottontail rabbits, rattlesnakes, tarantulas, burrowing owls, badgers and swift foxes, that often move into their burrows.

"Prairie dogs, talk of the town," will be broadcast as part of the Natural World documentary series at 20.00GMT on Wednesday 3 February on BBC Two.



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