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What Dogs are Saying with their Barks
Research explores animal sounds as a form of communication
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A sleep-deprived gentleman once asked me, “How is it that dogs can bark so long? When I yell for hours on end, I lose my voice.” Then he went on to describe the dogs in his neighborhood, whose barking bouts lasted longer than all of the Wagner operas combined.

Anyone who’s experienced an epic canine oratorio has probably wondered, “What’s going on? Do dogs just like to hear the sound of their voices?” Until recently, some researchers thought this was the case, taking the position that because dogs bark at almost anything and everything and for hours on end with no apparent reply, dog barking must not be a specific form of communication. Rather, barking is just a loud and obnoxious way for them to say, “Hey! Look at me!” More specific information, it was postulated, comes from reading body expression and olfactory messages.

Given the sparse number of studies on vocal communication in dogs, this contention seemed reasonable until consideration of the ever-expanding research on songbirds, ground squirrels and monkeys provided a very different view.

For decades, while some looked at dogs and pooh-poohed their barks as nuisance noise, others—such as Dr. Peter Marler, professor emeritus at the University of California, Davis, and a pioneer in the field of vocal communication in birds—were taking a closer look at the sounds that animals, including the common chicken, make. Says Marler, “Chickens are an obvious case … to most people, the sounds are a kind of noise, or vicarious vocalizations that have little meaning. But this view could not be more wrong. In fact, many studies show that chickens have a very rich and elaborate vocal repertoire, and that different calls mean different things.”

These studies started with the finding that roosters have specific types of predator-alarm-calls, one for aerial predators such as hawks, and another for ground predators. Play-back studies—in which hens hear taped versions of these calls in the absence of both a predator and visual signals from the rooster—show that the calls deliver specific information. Hens duck for cover upon hearing a recording of the aerial call and extend their necks and look for the danger when they hear the ground-alarm-call. These responses to the respective calls tell us the calls have specific meanings to those who hear them.

And those aren’t the only interesting chicken calls. Roosters also make a particular call when they find a morsel to eat, and this sound, part of the rooster’s courtship routine, serves to attract hens. As with the alarm calls, recorded food calls played back from behind a barrier with a hen on the other side will cause the hen to approach when she hears them. What’s more, states Marler, “If the calls were recorded from a male who had a very choice food item, like a cricket, she’ll approach faster than if the calls are given [for] a piece of grain or peanut. So the calls convey some information about food quality.” And, like the alarm calls, these differential responses indicate the calls have meaning.

But what about those calls, like barking, that go on and on with no obvious response from other animals? Dr. Don Owings, professor of psychology and animal behavior at the University of California, Davis, says, “Call communication can be organized on different time frames, so that you don’t see an immediate response to each vocalization. You have to look at the effect of signaling in a time frame that is appropriate for the signaling behavior.”

This longer time frame reveals interesting things. For instance, California ground squirrels respond to mammalian predators by uttering a chatter vocalization. Other squirrels respond by running to their burrow or standing up and looking around. If the predator lingers, the calling ground squirrels move from an erratically spaced, episodic chatter to a highly rhythmic “deet-deet-deet.” Observation reveals that individuals who hear the vocalization don’t startle or respond to each vocalization, and often return to their feeding and previous activities. However, Owings’ student, Jim Loughry, looked more closely at the overall activity and body postures over a longer time period and found that squirrels listening to this rhythmic vocalization were more vigilant overall. Even if they were eating, they would eat while sitting upright as they scanned their surroundings.

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