Chicken speak: birds pass test for fancy communication.
Older studies have hinted at this chicken power, notes Chris Evans of Macquarie University in Sydney, Australia. For example, he and his colleagues have shown that the particular clucks that chickens give when they find food inspire other chickens to search for it.
The old tests, however, left a nagging possibility that the clucks just trigger a reflex to search for food, Evans says. Now, he and Linda Evans, also of Macquarie University, have used a different approach that's "given us confidence," he says, to label the chicken clucks as representational signals.
Various researchers have linked various kinds of vocalizations to particular responses. The Evans lab, for example, found that chickens give different alarm calls depending on whether a scary intruder flies in or approaches along the ground. Other chickens look in the appropriate direction after each of those calls.
For the new tests, the Evanses went back to food calls. For example, males go "tck, tck, tck" upon discovering anything edible (hear audio at www.sciencenews.org/ 20061118/foodcall.aif). Hens then stalk over to investigate. They take a tidbit from a male's beak or stare intently at the ground. "They look like people who've lost their glasses," says Chris Evans.
In half the tests, the researchers scattered a few kernels of corn onto the floor. That's enough food for a hen to notice, but nowhere near enough to satisfy its craving. The hens ate the corn before hearing a male's clucks. In the other half of the tests, hens encountered no food.
After each hen heard a recording of a male's food call, those that had already received corn spent less than 3 seconds peering at the ground. But birds that hadn't been fed searched, on average, for 7.5 seconds.
The difference in response times reflected whether a bird already knew that food was available, so the call isn't an automatic trigger for some reflex to search the ground, the researchers argue. In contrast, a rooster's ground-intruder call didn't evoke different responses from the fed and unfed groups, the Evanses say in a paper available online and in an upcoming Biology Letters.
Primatologist Klaus Zuberbuhler of the University of St. Andrews in Scotland compares the results to those from his own test with monkeys. Once those animals heard monkey calls indicating one kind of predator, they responded with less commotion to recordings of that predator than to recordings of a different attacker. So, Zuberbuhler argues, these monkey alarm calls are likewise not just triggers of an automatic response.
Finding a similar effect in chickens' food calls is "wonderful" he says.
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|Title Annotation:||This Week|
|Date:||Nov 18, 2006|
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