Animals adapt their vocal signals to social situations

WASHINGTON — A special August issue of the Journal of Comparative Psychology, published by the American Psychological Association, presents a host of studies that investigate the way that animals adapt their calls, chirps, barks and whistles to their social situation.

The special issue, Acoustic Interaction in Animal Groups: Signaling in Noisy and Social Contexts, reports on findings from the natural world such as:

• 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), scientists 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.

• 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.

Review articles assess the evidence to date and outline future directions. For example, Peter Tyack, PhD, a biologist at the Woods Hole Oceanographic Institution, concludes that, "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." It could mean that mammals have more of the neural underpinnings for learning to vocalize than has been previously thought.

The Journal of Comparative Psychology publishes articles from a comparative perspective and features original empirical and theoretical research on the behavior, cognition, perception and sociality of diverse species. It is edited by Gordon Burghardt, PhD, of the University of Tennessee at Knoxville, where he is alumni distinguished service professor, Departments of Psychology and Ecology & Evolutionary Biology.

"Animal communication has been a major emphasis in animal behavior and comparative psychology for many decades," Dr. Burghardt says. "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."

Special Issue: "Acoustic Interaction in Animal Groups: Signaling in Noisy and Social Contexts." Journal of Comparative Psychology. Vol. 122, No. 3.

(Full text is available from the APA Public Affairs Office and at http://www.apa.org/journals/releases/com1223231.pdf)

Dr. Burghardt is on research leave until October 2008 and checking e-mail only periodically at gburghar@utk.edu. Guest editor Todd Freeberg, PhD, is available at tfreeber@utk.edu or by phone at (865) 974-3975.

The American Psychological Association (APA), in Washington, DC, is the largest scientific and professional organization representing psychology in the United States and is the world's largest association of psychologists. APA's membership includes more than 148,000 researchers, educators, clinicians, consultants and students. Through its divisions in 54 subfields of psychology and affiliations with 60 state, territorial and Canadian provincial associations, APA works to advance psychology as a science, as a profession and as a means of promoting human welfare.