Female mice indulge in polyandry

Contrary to the previous assumption that female mice are attracted more strongly to the odour of healthy males, a new study reveals that mice mate with unhealthy males as well.

"Until now, scientists generally assumed that females choose their mates depending on their males' scent or other secondary sexual traits. Our study shows that this isn't necessarily the case," said first author of the study Sarah Zala of the University of Veterinary Medicine, Vienna.

The females were allowed to freely choose between two males, one healthy and another challenged with a mild infection.

The majority of females, about 86 percent, were initially more attracted to the healthy males. However, unhealthy males were also chosen as mating partners.

"That surprised us. We assumed that the females would opt for the healthy males. Not only would this minimise the chance of becoming infected themselves, but choosing a healthy partner would also be advantageous for their offspring," Zala said.

A genetic analysis of the offspring revealed that about 30 percent of the litters had two fathers, the healthy male and the unhealthy one.

Many females apparently mate with both males, whether these are healthy or not.

"We suspect that the females do this to protect their young. A male that was rejected as a mating partner may commit infanticide in order to get another chance at siring offspring," Zala explained.

The situation could be different in the wild. As females recognise healthy males quite well based on odour, and are more attracted to them, they may be more likely to find healthy males in the wild, researchers said.