Dominant female mongooses can bully relatives to self-abort their litters

Washington, March 17 : A new study has found that the female banded mongooses torture pregnant relatives until these victims are often traumatized enough to self-abort their litters.

According to a report in Discovery News, the findings suggest that female bullying may frequently be tied to reproductive cycles and can benefit the aggressors if they take physical action.

Women in groups often enter estrus at around the same time, which in mongooses and our closest living animal relatives, chimpanzees, is an evolved phenomenon that helps to prevent infanticide "because females may risk inadvertently killing their own young if they attempt to kill the offspring of other females," according to lead author Michael Cant and his team.

But, peaceful group living among female banded mongooses falls apart when dominant, older females decide to kick subordinates out.

"Eviction events start suddenly when older dominant females turn on other females and start to repeatedly chase, scratch and bite them," Cant told Discovery News.

"Other group members, including males and subadults also join in, chasing and attacking the victims," he said.

The process continues for one to two days, with victims attempting to return home, only to be attacked more.

"Evictees can suffer quite nasty injuries and are often bleeding and limping by the end of the eviction," said Cant, a research fellow at the Center for Ecology and Conservation, University of Exeter in Cornwall.

"The process of being evicted is probably extremely stressful and we think that this physiological stress may be the mechanism that triggers spontaneous abortion," he added.

He and his team documented the behavior while studying 1400 banded mongooses living in 20 groups in and around Mweya Peninsula, Uganda.

The scientists believe that bullying breaks up the family home, but is a maintained behavior because it benefits the pups of dominant females.

These older dominant individuals tend to leave very young females alone, but often target "middle-aged" females between the ages of 2 and 5.

"We have shown that the survival rate of dominant females' pups between the ages of 1 month and 3 months declines with the number of subordinate breeders," Cant said.

"This is likely due to competition for limited resources and access to good helpers - 'escorts'," he added.

As for the kicked-out middle-aged females, those that abort their litters are sometimes accepted back into the group.

Mongooses that cannot rejoin sometimes form new groups with other bullied females and subordinate males that have left their own groups voluntarily.