Dogs aren't the only animals that bark, they are just the most famous. Deer, monkeys and even birds also bark but what makes dogs different is a subject of interest in a new evolutionary biology study.

In a recent Behavioural Processes paper, researchers have provided scientific literature with what they say is the first consistent, functional and acoustically precise definition of this household animal sound.

Kathryn Lord, a graduate student in organismic and evolutionary biology at University of Massachusetts Amherst, says, “We suggest an alternative hypothesis to one that many biologists seem to accept lately, which seeks to explain dog barking in human-centric terms and define it as an internally motivated vocalization strategy.”

But barking is not a special form of communication between dogs and humans, the authors state. “What we’re saying is that the domestic dog does not have an intentional message in mind, such as,‘I want to play’ or ‘the house is on fire,'” explains Lord.

Don't tell Lassie that. Timmy would never have gotten out of that well.

Instead, the researchers say barking is an auditory signal associated with an evolved behavior known as 'mobbing', a cooperative anti-predator response usually initiated by one individual who notices an approaching intruder. For example, A dog barks because it feels an internal conflict, an urge to run, as well as a strong urge to stand its ground and defend pups. When the group joins in, the barks intimidate the intruder, who often flees.

“We think dogs bark due to this internal conflict and mobbing behavior, but domestic dogs bark more because they are put, and put themselves into, conflicting situations more often,” she says.

They say the reason traces back to the first dogs that started hanging around human food dumps, 8,000 to 10,000 years ago. They would have experienced a serious disadvantage if they had run a mile away every time a human or other animal approached.

According to Lord, “In evolutionary terms, dogs self-selected the behavior of sticking around, overcoming their fear and being rewarded by getting to eat that meal before some other dog got it. Thus these animals allow people to get unusually close. The scared ones die while those less scared stay, eat, survive and reproduce. So they inherit the tendency.”

She adds, “By contrast, wild animals like wolves have a very long flight distance. They hear something and they run before you'd ever see them. Dogs hang around, but now they have committed to holding their ground and the closer an ‘intruder’ gets, the more likely mobbing is to occur rather than running away.”

An example of the domestic environment (rather than the dog’s own behavior) that increases barking is the animal stuck behind a fence with a person approaching, says Lord. “The dog may either feel anxiety or excitement at seeing a stranger but in either case the dog is prevented from approaching or fleeing. This creates conflict, and thus barking.”

They identify eight different parameters in three categories which must be met in order to classify a given vocalization as a bark. These include tonality, noise, pitch, volume or amplitude, abrupt onset and pulse duration, for example.

In their view, barking is not self-referential communication to convey a message, but a short, loud sound characterized by combining both noise and tonal sounds, which is unusual in animal calls.

This definition widens the bark’s usefulness as a functional behavior seen in many animals, though domesticated dogs display it more often. “Using this definition, even birds bark, and certainly many mammals besides canines, including baboons and monkeys, rodents and deer also bark,” Lord explains. “In a whole bunch of mammals and birds, what they do in such conflicted situations is bark.”

You think some segments of the religious community have a problem with evolution? Wait until pet owners who think their dog 'communicates' with them by barking read this article.

“We understand the objection when people say their dogs bark for supper or to get out and play,” Lord says. “Dogs do quickly learn the simple cause-and-effect relationship between their bark at 10 p.m. and the fact that you’ll get right up and take them outdoors. It’s true, but in our view it’s going too far to suggest the animal is intentionally referring to a specific activity. Rather, it has just learned cues, as it does when it learns to sit or beg for a treat.”