Rebels often live hard and die young. Such is the case for extreme athletes, out-of-control celebrities—and, according to a recent study, certain breeds of dogs. As a team of researchers from the University of Sherbrooke concluded in a paper slated for publication in The American Naturalist in June, “obedient (or docile, shy) breeds live longer than disobedient (or bold) ones.”
The finding, as the study asserts, reflects the product of more than two centuries of “extensive artificial selection.” Beyond physical appearance and reproduction capabilities, humans placed an emphasis on behaviour traits, breeding for everything from fighting to guarding to companionship. In time, a spectrum of breeds emerged, each with a distinct temperament: hounds, for instance, are known for their hunting prowess; pugs, meanwhile, have become popular lap dogs.
But it appears there were unintended consequences, too. By comparing life expectancy data (surprisingly easy to obtain, thanks to extensive mortality statistics compiled by a Swedish pet insurance company) with the trainability of certain breeds, the researchers found a link between obedience and longevity. Lead author Vincent Careau, a Ph.D. student in biology, offered several examples to illustrate the point: poodles, for instance, are about 30 per cent more docile than boxers and four times as likely to live past 10; the English springer spaniel, meanwhile, is 34 per cent more docile than the basset hound and twice as likely to see its 10th birthday. (Because smaller breeds generally live longer, Careau compared dogs of similar size.)
Whether obedience causes longevity or longevity causes obedience, however, is more difficult to discern—making this what Careau calls “a chicken and egg argument.” On the one hand, a dog who obeys its master is less likely to run into the street, for instance, and may be therefore more likely to live to a ripe old age. But, he says, it’s also possible dogs that are genetically programmed to live longer are more likely to stay put when told.
The study also found a link between a dog’s aggressiveness and its energy needs. While the correlation may seem rather intuitive (before he died last year, Careau’s adviser Don Thomas observed that it’s an adaptive necessity to have the “metabolic machinery to back up threats”), it runs counter to what’s commonly printed on pet food packages, where size is often the single determining factor in terms of a dog’s energy needs.
Though the findings could have implications for humans—do shy people live longer?—Careau is reluctant to make generalizations about the personality traits of certain gene pools or cultures. “It’s really a minefield,” he says. For now, he’s focusing on four-legged animals, currently testing his hypotheses on chipmunks and mice, which are much less likely to take offence.
Monday, May 31, 2010