While staying together with family and friends can be a rewarding experience for some voles, social interaction is merely tolerable to others. New research published in the journal eLife has explored how individual, sex, and species differences among voles influence their social lives.
Since similar hormones and brain structures are involved in social interactions in many species, including humans, this study can shed more light on some of the foundations of social differences.
According to scientists, some vole species, such as prairie voles, form long-lasting social bonds with their mates, as well as same-sex peers. On the other hand, meadow voles form social relationships only to help them survive the winter and part ways in warmer months.
“We wanted to determine why voles of these two species spend time in social contact,” said study first author Annaliese Beery, a biologist at the University of California, Berkeley. “Specifically, we wanted to know what role social motivation plays in their behavior, or to what extent social selectivity is more about avoiding strangers.”
In order to answer these questions, Beery and her team trained prairie and meadow voles to push a bar to receive food rewards. Afterward, they replaced the food with brief access to familiar voles or strangers to see how often they would push the bar to get access to the other animal.
The researchers found striking species and sex differences structuring the voles’ behavior. While female prairie voles worked harder to see familiar voles rather than strangers, male prairies voles did not show a preference for close acquaintances. Instead, they worked harder to approach females rather than males. The meadow voles, which were only females, did not seem very interested in any type of social interaction.
The results indicate that prairie voles found social interaction with familiar animals more rewarding, while the meadow voles, although likely to tolerate family or friends, did not seem to find much satisfaction in social interactions in general.
By analyzing the brain chemistry of these animals, the scientists discovered that variations in behavior were associated with concentrations of oxytocin – a hormone linked to sociality. While animals with more oxytocin receptors in a part of the brain called the nucleus ambiens were more social, those with more receptors in the bed nucleus of the stria terminalis were more aggressive.
“Knowing more about how the mechanisms supporting social relationships are similar and different across species and sexes will help us understand which mechanisms are universal and which are species-specific,” concluded Beery.