MELISSA BLOCK, HOST:
In recent years, new college grads have been hit hard by the slow economy. A lot of them have had to move back in with their parents. Chances are, most of them can't wait to leave. Well, many animals also have this instinct from bugs, to birds, to bears, but there's an exception. And as NPR's Adam Cole reports, adult prairie dogs don't mind living in their parents' burrows.
ADAM COLE, BYLINE: John Hoogland knows prairie dogs.
JOHN HOOGLAND: Frequently, I refer to prairie dogs as my little people.
COLE: In a remote corner of New Mexico's Valles Caldera National Preserve, he's about to embark on a new season of field research. He'll start the same way he has for more than 30 years - trapping, tagging and then releasing every prairie dog in his study colony.
HOOGLAND: We've now tracked over these years well over 30,000 prairie dogs, probably closer to 40,000.
COLE: Hoogland, the University of Maryland ecologist, has studied nearly every aspect of prairie dog life: alarm calls, mating, infanticide. But there's one subject that didn't interest him: dispersal. That's when animals leave the place they were born. It's of huge importance to ecologists, and hundreds of thousands of papers have been written about it. Maybe the most important of these was written by Robert May and William Hamilton.
HOOGLAND: Robert May and William Hamilton are superstars. We're talking about Mantle and Maris for baseball or, you know, Michael Jordan and Scottie Pippen for basketball.
COLE: They had a hypothesis. If you compete with your family members, the family won't do as well, and its genes are less likely to be passed on. So to avoid that competition, animals will leave home as soon as they can. This hypothesis has been proven over and over in fig wasps and lizards and mice. So Hoogland just assumed prairie dogs followed the same pattern, and he never would have taken a closer look if it weren't for the social dynamics of human mating pairs.
HOOGLAND: My wife said to me - we talk about prairie dogs all the time - and she said, you know what, that dispersal by females isn't happening very often. And I remember saying to Judy, I said, you know, there's nothing there. I'm not going to waste my time doing that. Well, my wife can be very persistent.
COLE: And so Hoogland crunched the numbers, publishing the results in the journal Science. His 30 years of data showed that prairie dogs weren't leaving home. Now, you often hear about females staying with their family groups, but even in those situations, they'll only stick around if there aren't too many relatives crowding up the place. But here, in females of three prairie dog species, the opposite was true: the more relatives, the merrier. Prairie dog males tend to leave their home burrows to find mates, but even they were more likely to stick around.
So why do prairie dogs buck the trend? Researchers aren't entirely sure, but Ana Davidson, a prairie dog researcher and conservationist at Stony Brook University, says the benefits of prairie dog family life outweigh the costs of competition. For example, prairie dogs groom each other, removing parasites that carry disease.
ANA DAVIDSON: That grooming is part of the connection that the animals create with each other.
COLE: It's PDA, prairie dog affection. Sisters will help each other maintain their burrows. And if a new mother dies, her female relatives will nurse her babies. Then there's defense.
DAVIDSON: Prairie dogs are able to alert each other of predators.
COLE: And if a prairie dog sees a badger closing in on a close relative, it's more likely to let out its blood-curdling warning cry.
(SOUNDBITE OF PRAIRIE DOG CRYING)
COLE: With a family like that, why would you ever want to leave? Adam Cole, NPR News.
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