It takes the prairie vole four months to get over his ex

Prairie voles live and preferentially mate with a single (pair-bonded) partner. They also jointly rear pups. However, male voles mate with females they are not pair-bonded to, and can occasionally pair-bond with a second female if the first partner dies.

A study by Kelsey Harbert et al. investigated how prior bond experience influenced the trajectory of new pair bonds. To do this, they first paired sexually naïve voles and then separated them. After a variable amount of time post separation, the males (N = 58) were introduced to new females. In a test of their fidelity, the males were allowed to freely interact with either their original partner or a novel female, positioned at two ends of an apparatus.

Males spend the majority of their time cuddling with and in proximity to their chosen pair-bonded female. Hence, the ratio of time spent with the pair-bonded female to the time spent near either females was used as a measure of the strength of the pair-bond.

In most of the interactions, researchers found a "rebound effect", wherein animals initially showed a preference for the novel female, but chose to go back to their original partner. The males only pair-bonded with the novel female (partner 2 supplanted partner 1 as pair-bond) if a minimum of 4 weeks had passed since separation. Read more about the study here.