Unfaithful Mouse Spouse? Talking it through calmly is best, say researchers

Talking infidelity through calmly seems to be the best approach to save the relationship–at least for mice living in California…

The quality of conversations between California mice couples after one partner has been unfaithful can help predict which mouse pairs will successfully produce a litter of mouse pups and which males are good fathers, according to a new study on the evolution of monogamy.

Successful mouse couples talk out infidelity in calm tones

California mice are relatively solitary animals, but put two in a room and they’ll talk each other’s ears off. And while all the cooing, chirping and barking they use to woo mates or drive off enemies is at too high a frequency for human eavesdroppers to hear, they may speak volumes about the way the mice form relationships. The quality of their conversations after one partner has been unfaithful can help predict which mouse pairs will successfully produce a litter of mouse pups and which males are good fathers, according to a study published recently by the journal Frontiers in Ecology and Evolution in a special issue on the evolution of monogamy.



The California mouse is known for its monogamy. Most rodents are promiscuous, but in the wild, infidelity is unheard of among the California mouse. Once they’ve bonded with a partner in their natural habitat (scrubby woodlands in California and northern Mexico), they don’t mate with other another mouse unless their partner dies.


The study

The researchers introduced an otherwise unknown factor in California mouse relationships: cheating.

Some of the males were moved to live with new females, and some of the females were moved to live with new males. Another group was separated, but not housed with new potential mates. A fourth group was left together.

After a week, the mice given the opportunity for infidelity were reunited, and the researchers set about recording interactions again.


The findings

“Compared to when they were nice and sweet before separation, when they came back with their original mates the pairs were aggressive. But there was a range. Some of the pairs that had the infidelity encounter were barking a lot, but some of them were much closer to their pre-separation levels of simple sweeps and sustained vocalizations.

–Dr. Josh Pultorak


Importantly, it was how the reunited couples worked out the events of their separation that predicted whether they’d have baby mice together.


“The pairs that successfully produced litters were the ones that were affiliative when reunited. The ones that showed more aggression were far less likely to produce offspring. That’s a big deal. Arguably, it’s the whole point of forming pair bonds in the first place.”

-Dr. Josh Pultorak


Additional findings

The researchers also gave the males a fatherhood test, moving a newborn away from the family to see how quickly the dad would respond to comfort, groom and warm the pup.


“The more affiliative or ‘loving’ and resilient a pair was after that infidelity experience, the faster the male was in responding to a pup’s needs. They were better dads.”

–Dr. Josh Pultorak


Journal Reference: Joshua D. Pultorak, Sarah J. Alger, Steven O. Loria, Aaron M. Johnson, Catherine A. Marler. Changes in Behavior and Ultrasonic Vocalizations During Pair Bonding and in Response to an Infidelity Challenge in Monogamous California Mice. Frontiers in Ecology and Evolution, 2018; 6

Study: DOI: 10.3389/fevo.2018.00125



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