Natural Selection: Genetic Variation Allows Male Prairie Voles To Be Faithful Or Stray From Mate

Prairie voles are small Midwestern rodents that are often recognized in popular culture for their monogamous relationships, where males and females form pair-bonds and share the responsibilities of raising their young. While all that it generally true, relationship status doesn't stop some males from seeking additional sexual partners.

In a recent study, researchers from the University of Texas at Austin found these behavioral differences stem from genetic predispositions in their brains. Natural selection, researchers say, has driven this genetic variation and allowed for both monogamous and non-monogamous voles to co-exist, rather than favoring one set of characteristics over another, according to a news release. 

"This brain variation isn't just there by chance. It isn't random," Steven Phelps, associate professor of integrative biology and the lead investigator on the study, explained in the release. "It's actually something that selection has kept around for a very long time. When it comes to social behavior, maybe there isn't a normal brain."

For their study, researchers compared voles that stray and produce more offspring with multiple partners to those involved in a committed relationship and remain at home to take care of their young. Since neither mating strategy proves to be inherently more successful, both types have persisted throughout the rodent's evolution but the choice to "stay or stray" ultimately comes down to differences in DNA that turn genes on and off in the brain region responsible for spatial memory. Simply put, some voles are hardwired for wide open spaces and new relationships.

"All of animal neuroscience is kind of predicated on minimizing genetic variation," Phelps added in the university's release. "When we did this simple thing of going out in nature and looking at the brain, we were shocked at what we found." 

However, their findings confirm nature favors both brain types, thus increasing the genetic diversity of prairie voles. 

"I wouldn't be surprised if there were many genes whose variants have been kept around by selection in a similar way," Phelps concluded. "We may find this to be a common pattern in social behavior, including personality differences, in lots of species."

Their study was recently published in the journal Science.

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