Both male and female banded mongooses risk being exiled from their social groups when reproductive competition is high. Researchers from the University of Exeter found that these evictions can be very violent and often result when subordinates step on the toes of their dominant family members.
For the past 16 years, researchers monitored the interactions of a population of wild banded mongooses in Queen Elizabeth National Park, located in southwest Uganda.
Banded mongooses live in cooperatively breeding family groups, meaning all group members contribute to raising pups, even if they don't breed themselves. Adult females breed together and even give birth to a communal litter on exactly the same day, too.
Generally, mongoose social groups live in harmony, working together to forage and care for the young. However, the recent study from Exeter suggests that this peace can quickly erupt into violence.
"Banded mongooses, like many social animals, often show extreme levels of cooperation but occasionally these harmonious relations break down," lead author Faye Thompson, a Ph.D. researcher at the University of Exeter's Centre for Ecology and Conservation, explained in a news release. "Dominant females, and sometimes males too, aggressively evict members of their own family to reduce their level of reproductive competition."
For instance, dominant animals will often kick subordinates out of the social group when they cannot stop them from breeding. A group of females is also likely to be forcibly removed from the group when there are lots of breeding individuals, and a group of males often joins them in exile when there are a lot of males rivaling for mates. It follows then that eviction is a major source of gene flow in social animals.
"Banded mongooses rarely disperse of their own accord, and so eviction is one of the only ways that individuals form new groups," Thompson added. "These eviction events result in the mass movement of genes through the population."
The stakes are high for breeding banded mongooses. Previous studies of banded mongooses revealed that females will risk their lives to mate with rivals during pack "warfare" and that both males and females have learned to avoid inbreeding when mating within their own social group by distinguishing between relatives and non-relatives.
"We've been studying these animals for 20 years, but it's only now that we are beginning to understand the long-term dynamics of the system," Professor Michael Cant, who leads the University's Banded Mongoose Research Project, concluded. "This work shows that within-group conflicts can have effects not only on the individuals involved, but also on the genetic structure of the wider population."
Their findings were recently published in the journal Proceedings of the Royal Society B.
