Wired to Wander
Prairie voles are small animals known for their monogamy — they have a primary partner and raise their young as couples. But while some males stay fully faithful to their partner, others also mate with other partners. When researchers under the direction of Steven Phelps, associate professor of integrative biology, looked for a cause to these disparate behaviors, they found that the brains of the monogamous male voles and the multiple-partner voles are actually different.
The prevailing wisdom of animal neuroscience says that when a species has contradicting traits, such as philandering and monogamy, natural selection will favor genetic markers for the trait that helps the species get ahead. But what happens when a trait has its pros and cons? Monogamy allows the male vole to make sure that his pups are all his, but seeking out multiple partners allows a vole to have more offspring than usual. Because both strategies have drawbacks and benefits, Phelps and his team showed that natural selection encourages the diversity.
“This brain variation isn’t just there by chance,” said Phelps. “It isn’t random. 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.”
Phelps notes that what is true for voles may well happen in other species, as well, as natural selection supports genetically driven differences in the brain.
“I wouldn’t be surprised if there were many genes whose variants have been kept around by selection in a similar way,” Phelps says. “We may find this to be a common pattern in social behavior, including personality differences, in lots of species.”