When two opposing mongoose "armies" decide to face off, the ensuing brawl rivals a human battle. Often, blood is shed as the winning pack isolates and converges on the lone male mongoose that dared to take a stand.
But under the cover of battle, a female mongoose slips off, eager to find a mate to diversify her offspring's genes and increase the likelihood of survival in this cruel world.
Welcome to the aggressive realities of life and love among banded mongooses.
According to a study published Monday in the journal Proceedings of the National Academy of Sciences, this collective violence is incredibly common among banded mongooses. And, perhaps surprisingly, it's the female leaders — not the males — that drive this behavior.
"Our data suggest that the benefits of initiating fights with neighboring groups far outweigh the costs for females: females suffer lower mortality costs than males, and also enjoy fitness benefits from mating with extra-group males," Faye Thompson, co-author of the study and Associate Research Fellow at the University of Exeter, tells Inverse.
The study focuses on a population of banded mongooses (Mungos mungo) living in Queen Elizabeth National Park, Uganda. The data were collected over a nearly 20-year-period, between January 2000 and March 2019.
These particular mongooses dwell in underground burrows of roughly 20 adults (plus offpsring), banding together to give birth, raise young, and defend their group from predators.
Banded mongooses rarely ever depart the group, unless they are forcibly expelled or, even more rarely, leave of their own volition.
This dynamic increases the group's chances for survival overall, but it also severely minimizes the genetic diversity in the group, making it difficult for females to find non-related males for mating.
To ensure the survival of their species, female banded mongooses covertly seek out rival groups to find suitably unrelated male mongooses for reproduction.
But to achieve their mission, they turn to particularly violent means.
Leading to death - When female mongooses are in "heat" (otherwise known as "estrus"), so-called "mate-guarding" males in their group will follow them "nose-to-tail" pretty much all the time, Thompson says.
This kind of chaperoning makes sneaking off hard — but it also provides the perfect out. Female mongooses seemingly guide their male chaperones into enemy territory on purpose.
"Data suggests that reproductive females exert greater influence than males in group leadership decisions...meaning that females can lead their whole group into enemy territory to seek out intergroup interactions that are beneficial for them but not for the males in their group," Thompson says.
Scientists refer to this kind of behavior as exploitative leadership, since the female mongooses rarely ever sustain damage in these attacks, but instead, put their male followers in danger of injury or even death —especially if they become separated from the group.
Up to 10 percent of adult mongoose deaths result from these encounters, though that number gets as high as 20 percent for juveniles.
But from an evolutionary standpoint, the clever female mongoose's ends justify the means.
"We know that pups born to fathers from outside their group have higher survival than pups from within-group males, so perhaps this benefit in terms of group recruitment outweighs the mortality costs that the group suffers," Thompson notes.
Just like us - The researchers compared the female mongooses' behavior to other types of social mammals — most of whom do not resort to lethal inter-group disputes.
But some mammals do lean into the bloodshed. Wolf packs, for instance, get very violent when fighting each other, and so do we humans. War resulted in death for 14 percent of the hunter-gatherer populations from the late Pleistocene and Early Holocene period surveyed in this study, and 18 percent in early, small-scale human settlements.
"Our study shows that ‘warmongering’ by exploitative leaders is not a uniquely human trait and that leadership of this kind can explain why we see very damaging levels of conflict among some animal societies, specifically banded mongooses," Thompson says.
There are disturbing parallels between the female banded mongooses — who lead their followers to harm's way for their own benefit — and human leaders sending soldiers to their death.
"In humans, leaders might gain an unequal share of resources or status from war, while avoiding costs that are suffered by other members of society," Thompson says.
And when these leaders become detached from the violent consequences of war, that spells greater destruction for society.
"There are many ecological and social factors that may have shaped patterns of human warfare, but our study shows that where leaders are decoupled from the costs that they incite, then intergroup violence can be frequent and destructive," Thompson adds.
Abstract: Collective conflicts among humans are widespread, although often highly destructive. A classic explanation for the prevalence of such warfare in some human societies is leadership by selfserving individuals that reap the benefits of conflict while other members of society pay the costs. Here, we show that leadership of this kind can also explain the evolution of collective violence in certain animal societies. We first extend the classic hawk−dove model of the evolution of animal aggression to consider cases in which a subset of individuals within each group may initiate fights in which all group members become involved. We show that leadership of this kind, when combined with inequalities in the payoffs of fighting, can lead to the evolution of severe intergroup aggression, with negative consequences for population mean fitness. We test our model using long-term data from wild banded mongooses, a species characterized by frequent intergroup conflicts that have very different fitness consequences for male and female group members. The data show that aggressive encounters between groups are initiated by females, who gain fitness benefits from mating with extragroup males in the midst of battle, whereas the costs of fighting are borne chiefly by males. In line with the model predictions, the result is unusually severe levels of intergroup violence. Our findings suggest that the decoupling of leaders from the costs that they incite amplifies the destructive nature of intergroup conflict.