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Study: Prairie voles more comfortable, less stressed in numbers than alone

"Crowding usually forces territorial animals to compete more fiercely for limited supplies," explained researcher Dimitri Blondel.
By Brooks Hays   |   Updated Jan. 19, 2016 at 6:14 PM

RALEIGH, N.C., Jan. 19 (UPI) -- There's no such thing as social anxiety inside a prairie vole den.

New research suggests prairie voles are most comfortable when packed into close quarters, surrounded by their friends and family.

The new findings -- published in the journal General and Comparative Endocrinology -- are part of a larger effort by Duke University scientists to measure the physiological effects of crowding and isolation in animals, including humans.

Because prairie voles are believed to form monogamous pairs, mating for life, they're frequently studied by biologists looking for insights into the nature of social bonding.

To see how the mammals responded to varying levels of congestion and isolation, researchers monitored the stress levels of voles as they lived among varying numbers of their peers. A system of enclosures was used to coral and confine the animals into smaller or larger spaces, while fecal testing helped scientists track the changing levels of a stress hormone called corticosterone.

Radio collars monitored movement, and showed that as the voles were forced to share a smaller amount of space with a greater number of their peers, they tended to bump into each other more often.

But the fecal testing proved they didn't mind the traffic jams or collisions. In fact, crowded voles were the least stressed. When researchers tripled the density of voles, stress hormone levels shrunk by 20 percent.

Researchers got the same results in the summer and the fall.

"Crowding usually forces territorial animals to compete more fiercely for limited supplies of things like food, mates and prime sleeping or nesting spots," study author Dimitri Blondel, a postdoctoral researcher at Duke, said in a press release.

Blondel thinks isolation may cause voles to worry about the difficulty of finding a mate. Prairie vole populations rise and fall in erratic fashion. The boom and bust cycle may influence how the mammals perceive and react to population density.

A dwindling number of nearby peers may also signal to the voles that a predator, like a snake or hawk, is actively hunting. An anticipatory boost of corticosterone may prep the vole for the flight or fight response.

"If you were on a deserted street at night, you might have a higher stress level than if you were in a crowd of 20 people walking down the street," Blondel said.

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