Testosterone promotes 'cuddling,' not just aggression

Aubrey Kelly et. al conducted experiments on Mongolian gerbils, rodents that form lasting pair bonds and raise their pups together. While males can become aggressive during mating and in defense of their territory, they also exhibit cuddling behavior after a female becomes pregnant, and they demonstrate protective behavior toward their pups.

In one experiment, a male gerbil was introduced to a female gerbil. After they formed a pair bond and the female became pregnant, the males displayed the usual cuddling behaviors toward their partners. The researchers then gave the male subjects an injection of testosterone. They expected that the resulting acute rise in a male's testosterone level would lessen his cuddling behaviors if testosterone generally acts as an antisocial molecule.

"Instead, we were surprised that a male gerbil became even more cuddly and prosocial with his partner," Kelly says. "He became like 'super partner.'"

In a follow-up experiment a week later, the researchers conducted a resident-intruder test. The females were removed from the cages so that each male gerbil that had previously received a testosterone injection was alone in his home cage. An unknown male was then introduced into the cage.

"Normally, a male would chase another male that came into its cage, or try to avoid it," Kelly says. "Instead, the resident males that had previously been injected with testosterone were more friendly to the intruder."

The laboratory experiments, in a sense, slowed down what the males might experience almost simultaneously in the wild. In their natural habitat, Kelly explains, mating with a partner elevates testosterone, which primes them to act cuddly in the moment and in the near future while living with their partner, even if the testosterone levels decline.

The current study also looked at how testosterone and oxytocin interact biologically. The results showed that the male subjects receiving injections of testosterone exhibited more oxytocin activity in their brains during interactions with a partner compared to males that did not receive the injections.

Ref:

Aubrey Kelly et. al,Beyond sex and aggression: testosterone rapidly matches behavioral responses to social context and tries to predict the future,Proceedings of the Royal Society B Biological Sciences, DOI: 10.1098/rspb.2022.0453