Social situations shape animals' vocal signals

Washington, Aug 26 : A host of studies have identified the way animals adapt their calls, chirps, barks and whistles to their social situation.

Researchers found that male gray treefrogs (Hyla versicolor) give out longer but fewer calls in reaction to the calls of other males.

In other words, when these frogs are chorusing full blast, a male seeking female attention will change the rhythm of his call to break out of the chorus.

Using an array of microphones to identify individual callers among wild bottlenose dolphins (Tursiops truncates), researchers found that although dolphins whistle more in social situations, individuals decrease their vocal output in large groups, when their whistles are more likely to be drowned out.

Nestling tree swallows (Tachycineta bicolor) adjust their call output to parents when there's more noisy competition from the brood.

Researchers found that carolina chickadees (Poecile carolinensis) in larger social groups use calls with greater information than do individuals in smaller groups, and female-male interactions in opposite-sex chickadee pairs reflect the rate of male production of that distinctive chick-a-dee call.

Two different species of North American katydids synchronize calls within species, using somewhat different methods.

Whereas the synchrony of N. spiza is a byproduct of signal competition between evenly matched males that of N. nebrascensis seems to be an adaptation that allows cooperating males to make sure females can pick up critical features of their calls.

These different routes to synchrony suggest different evolutionary paths that have led to the way that male katydids acoustically advertise their availability.

"Pooling data on vocal imitation, vocal convergence and compensation for noise suggests a wider [cross-species] distribution of vocal production learning among mammals than has been generally appreciated," Peter Tyack, PhD, a biologist at the Woods Hole Oceanographic Institution.

It could mean that mammals have more of the neural underpinnings for learning to vocalize than has been previously thought.

Gordon Burghardt, PhD, of the University of Tennessee at Knoxville, said: "Animal communication has been a major emphasis in animal behaviour and comparative psychology for many decades."

"However, in recent years, we have gone beyond the straightforward analysis of dyadic interactions between two individuals. We now consider the role of eavesdropping, deception and noisy environments in shaping signals and investigate how animals deploy them in various contexts," he added.

The study is published in an August issue of the Journal of Comparative Psychology.

ANI