Female banded mongooses instigate fights with neighboring social groups so they can mate with the males of the opposing group while the fur is flying, reports Donna Lu of New Scientist.
Violent battles with rival family groups are part of life for the banded mongoose, a five-pound, cat-like predator native to Africa that is famous for facing off with venomous snakes. These battles pit one group, usually around 20 individuals, against another in a conflict that can last hours and end in death for some combatants—usually the males.
Banded mongooses go to war with nearby groups up to three times a month, per New Scientist. Groups preparing to fight will assemble into battle lines, writes Christina Larson for the Associated Press (AP), until one side charges.
“Then they bunch up into writhing balls, chaotic and fast-moving, and you hear high-pitched screeches,” Michael Cant, a biologist at the University of Exeter who co-authored the new research, tells the AP. “We call it mongoose warfare.”
To learn more about what made banded mongoose fight these costly battles, Cant and his colleagues combined field observations with 19 years-worth of demographic and behavioral data for about a dozen mongoose families in Queen Elizabeth National Park, Uganda, according to the AP.
The researchers found that the fights were predominantly started by females, who wield a great deal of influence over the group, according to the research, published this week in the journal Proceedings of the National Academy of Sciences. This influence is particularly great when females are ovulating and capable of becoming pregnant, which in banded mongooses happens for all female group members at the same time.
Video taken by the researchers revealed that females mated with the males of rival groups during battle, while the protective males in their own group were distracted, per New Scientist. Fights were more likely to occur when females of a group were in the fertile stage of their reproductive cycle, called estrus.
“Estrus females have been observed to lead their group deep into enemy territory, closely followed by mate-guarding males, directly inciting intergroup fights,” write the researchers in the paper.
This betrayal may sound particularly upsetting, but it serves an important biological function. For banded mongooses, mating with males outside their own group is vital to the genetic health of the group because each member is born into their role, meaning group members are all somewhat related. Group members virtually never defect, which sets up something of a problem when it comes to the group’s genetic diversity. As time goes on, they become more and more inbred, which can cause harmful genetic defects to build up in the group.
Through genetic analysis, the researchers even found that females are more likely to conceive the next generation with a male from another group when there is a high risk of inbreeding in their own group. The analysis also revealed around 20 percent of pups in a given group are fathered by males from other groups, per the AP.
The dark side of this behavior is that it’s the males who do most of the fighting, and dying, in violent conflicts that the females start to gain access to fresh genes. In a statement, Cant says this is an example of exploitative leadership, in which the female leaders benefit but the rest of the group suffers—pups are also frequent casualties in the fights.
"A classic explanation for warfare in human societies is leadership by exploitative individuals who reap the benefits of conflict while avoiding the costs,” says Cant in the statement. "In this study, we show that leadership of this kind can also explain the evolution of severe collective violence in certain animal societies."