Prairie Voles Prefer Crowded Quarters, Researchers Say

Small prairie voles find comfort and releive stress in their crowded burrows, say researchers from Duke University whose recent study adds to the our understandding about how social stresses induced by crowding or isolation affect brain chemistry and behavior in many species, including humans.

Prairie voles are small mouse-like rodents that nest under shallow meadows and grasslands in the American Midwest and Canada. These critters have been the subject of multiple experiments focussing on genetics, physiology and social bonds since they often mate for life.

In the latest study, a team of scientists led by postdoctoral researcher Dimitri Blondel observed prairie voles living in fenced enclosures in a hayfield in southern Illinois. Removable gates were used to either divide or connect the enclosures and corral the animals into smaller or larger spaces.

For a period of three weeks, a dozen prairie voles were monitored in either a small enclosure, where there were roughly 97 animals per acre, or a large enclosure, where there were 32 animals per acre. Each rodent was fitted with a radio tracking collar, and scientists collected fecal samples to be analyzed for the presence of a stress hormone known as corticosterone. (Scroll to read more...)

While living in close quarters the voles bumped into each other nearly twice as often but stress hormone levels fell by roughly 20 percent. Researchers were initially surprised by these results, since increased anxiety and stress is linked to crowding. 

"Crowding usually forces territorial animals to compete more fiercely for limited supplies of things like food, mates and prime sleeping or nesting spots," Blondel explained in a statement.

Prairie voles may be the exception to Blondel's observations because their populations fluctuate – from a handful of individuals to several hundred per acre. Researchers suggest voles may interpret too much elbow room as a sign that predators are in the area and they need to flee, or as a sign they will need to spend more time and energy finding a mate.

"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 added.

The study was recently published in the journal General and Comparative Endocrinology.

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