Dog Bark Study Confirms What Everyone Already Knows?
Dog Bark Study Confirms What Everyone Already Knows?
© 2002 Sophia Yin, DVM, MS
New study shows dogs have a repertoire of barks that occur in specific contexts, read recent headlines. Findings spark interest among dog owners and animal behavior researchers alike, but to old-timers in the bowser business it's old news. Says one such sourpuss, "It just confirms what we already know."
Could it be that some misguided scientist, me, wasted several years and thousands of dollars studying something that's no news to people in the know? Not likely.
Despite our daily dealing with dogs, the history of vocal communication research on these household hounds ranks nearly last in terms of length. As we learn more about cowbirds, macaques and even common chickens, the list of what we don't know about dogs grows longer.
For instance, a slew of studies show that chickens have a complex set of informative calls, starting with their two alarm calls - one for aerial predators such as hawks and another for ground predators. Both hens and roosters cluck the repetitive ground predator call but the aerial alarm seems rooster-specific. Field studies show that cocks are most likely to call if hens are near. They also call more reliably when their testosterone levels are high.
You could conclude that the alarm call differences are due to the cock's motivational state and have no specific meaning. However, playback studies in the lab where hens hear the different calls in the absence of a predator and in the absence of visual signals from the rooster show that the calls deliver specific information. When hens hear the aerial alarm, they duck for cover or just crouch and freeze while tilting their head to scan the sky. When they hear the ground predator alarm they stretch their necks while standing tall and strain to see the source of excitement.
Roosters also make a specific food call when they find a morsel to eat. Then in a ritualized "tidbitting" display that gives the impression that cocks have an IQ roughly equal to that of an eggplant, they repeatedly drop and pick up the morsels while the hens rush in and out grabbing the bits away. Technically this call could just mean, "Come here," like a contact call and the visual display could tell the hens to take the food. When researchers played recordings of food calls to hens though, the hens looked down as though they were looking for food.
These studies show that chickens have a series of calls that refer to specific objects or situations. Since the calls could actually mean "Duck for cover" or "Look down" instead of "Hawk overhead," or "Food on the ground," though researchers call them functionally referential. They refer, functionally, to a specific object or situation.
Animals such as vervet monkeys and ringtailed lemurs also have functionally referential alarm calls, but separate calls for separate predators doesn't confirm that this is the case. California ground squirrels have different calls for aerial predators and ground predators but squirrels give the aerial alarm if ground predators are in hot pursuit and give the ground alarm if a hawk is flying far away. Thus their calls refer to how urgently they should respond rather than the specific type of predator.
Studies have also uncovered answers as to how animals learn to communicate. One set that spans a decade or two involves cowbirds - birds notoriously known for chucking eggs out of other bird nests and replacing them with their own, thus tricking others into fostering cowbird babies. One study found that young males raised with females but in the absence of adult males learned songs that researchers deemed demented since they sounded different from normal cowbird songs. When they played recordings of these songs and songs from adult birds of known breeding success though, they found that females really fell for the "deficient-sounding" songs. Several more studies set the situation straight. Young male cowbirds learn which songs to sing by watching their adult female tutors. The youngsters try different songs and when the lady cowbirds give their approving nods they know they've hit the right ones.
Male cowbirds all learn the super-songs but only a select few - the higher ups - are actually allowed to sing them. Since the juvenile males that are raised singly are socially retarded they sing the super-songs all the time, even when first placed in a group. A few pecks from the high-status singers teaches them to temper their tunes.
Surprisingly, when these juveniles are allowed to sing their desired song, they still don't get the girls, because in cowbird terms, they sing like Pavarotti but dance like a potato. They have to learn to perform the courtship routine - which consists of for one, facing the female when they sing - from adult males.
These are just a few of the findings we haven't yet explored in dogs. With more research and funding for it though, hopefully we'll eventually know at least as much about communication in domestic canids as we do in chickens. But it all starts with a simple study showing dogs have different barks in different contexts.
For information on where to donate funds for research on behavior in dogs, contact Benjamin Hart
Program for Companion Animal Behavior,
University of California, Davis
Davis, CA 95616
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