杏吧原创

Timmy is not the only one who can translate Lassie鈥檚 bark 鈥� dogs themselves also seem to discriminate between the yaps of other pooches.

That鈥檚 the conclusion of a team of Hungarian researchers who have measured the heart-rate fluctuations of pet dogs while playing them recordings of dogs barking at strangers and dogs barking to get attention.

鈥淚f we find that dogs can discriminate between barks, it might be that they also understand,鈥� says , an ethologist at E枚tv枚s Lor谩nd University in Budapest, who led the study.

It鈥檚 no secret that animals talk to one another. Prairie dogs, for instance, use an elaborate communication system that can distinguish between coyotes and humans. But researchers know far less about barking, a call unique to dogs, says Pongr谩cz.

Racing hearts

In 2005, Pongr谩cz鈥檚 team showed that humans can tell between a dog barking at a stranger ( hear audio) and one when they are alone ( hear audio). They even created a computer program to decipher barks.

To see if dogs could make the same distinction, Pongr谩cz played the two types of barks to 14 dogs hooked up to heart monitors. The hounds included German shepherds, golden retrievers, and several other breeds. All heard the barks of a Hungarian herding dog called a Mudi.

With a pup sitting in a room with its owner, Pongr谩cz鈥檚 team played several dog barks, each a minute apart.

When the dogs first heard the 鈥渟tranger鈥� bark their hearts raced. As the researchers played the same sound over and over, a dog鈥檚 heart rate tended to rise slightly then quickly return to normal.

Each successive 鈥渟tranger鈥� bark provoked less and less of a reaction, on average. However, when the dogs were played the 鈥渁lone鈥� bark, their hearts started racing again.

Alert call

Pongr谩cz interprets the heart-rate changes as evidence that the dogs understand the difference between the two kinds of barks. He also noticed that the animals tended to turn their heads toward the speaker only when they heard a new kind of bark.

Hearing certain barks might put a dog on alert, Pongr谩cz says. 鈥淲e thought the 鈥榮tranger鈥� bark has some kind of relevance for other dogs, because it鈥檚 quite interesting to them that somebody came,鈥� he says.

, a behavioural psychologist at the University of Florida in Gainesville, US, says that the heart-range changes suggest that dogs notice a difference in barks, but he would like to see more behavioural data to make the case even stronger.

Still, Pongr谩cz鈥檚 conclusion seems likely: 鈥淚f we can hear a difference, it seems to me, surely other dogs can pick it up,鈥� he says.

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