Why do dogs bark? It may sound like an existential query or a Zen koan, but the question has long puzzled animal behaviorists. Wolves, after all, only make sounds occasionally. So why do their domesticated cousins feel the need to make their presence heard on such a regular basis?
In a paper just published in the journal Behavioural Processes, a research team led by Kathryn Lord of the University of Massachusetts, Amherst, presents a thought-provoking new theory. Barking, they write, is a type of warning signal, traceable in evolutionary terms to the common ancestors of wolves, dogs, jackals and coyotes. It’s also a sign of internal conflict, a surprising finding that suggests canines have more in common with Woody Allen than was previously imagined.
Specifically, Lord and her colleagues propose that barking is a signal associated with mobbing, a form of cooperative defensive behavior engaged in by many birds and mammals. A predator, or some other unknown entity, will approach a group of animals; the first to notice its presence will alert the others “by means of vociferous and conspicuous vocalization.” Others will then warily approach the intruder, and as a group, they will threaten it both vocally and through movement until it retreats.
“Mobbing tends to occur in situations where the animal has conflicted motivations,” the researchers report. If a threat is obvious, animals will generally run, but if they’re uncertain whether a strange sound really represents danger, mobbing is a prudent alternative. It’s also an animal’s preferred option in cases where it cannot flee, as when a parent is protecting its infants, or — and here’s the connection to Fido — when its ability to move is restricted.
“Dogs are routinely confined or constrained with no opportunity for escape,” Lord and her colleagues write. “Kept in a kennel, a crate, a house, a fenced yard or tied up, they cannot run from approaching unfamiliar ‘intruders’ who are virtually omnipresent in human environments.
“The relatively close living quarters of captive dogs thus facilities group vocal response to a mobbing signal, accounting for the cacophony that often follows the initial barking of a single animal.” The other dogs on the block pick up the signal that a potentially dangerous intruder is near and add their voices to the choir of intimidation.
Adding bite to their argument, the scholars reference earlier research that “free-living ‘village dogs’ in non-Western societies … are not constrained or confined and exhibit much lower levels of barking.”
“It’s not only the environment (kennels, crates, fences, etc.) that increases conflict, but also domesticaton itself,” Lord said in a follow-up message. “Dogs, due to their domestication, are more likely to place themselves into conflicting situations (e.g., by not running away as soon as wild animals would).”
Lord believes “there is no intentional meaning behind the bark. The difference in bark sound structure is merely a result of where the dog falls along the aggressive/friendly conflict scale. If a dog is uncertain and leaning towards the aggressive end of the spectrum, it will produce a deep, noisy bark. If it is uncertain and on the friendly side of the spectrum, it will produce a high-pitched, tonal bark.” Bottom line: The different barks are not “an evolutionary adaptation for communication with humans, as has previously been suggested.”
Of course, dog owners may disagree. This provocative paper is surely not the last yelp on this subject.
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