Groups of mongooses band together to wage war on each other
War is not just a human activity. Costly group fights also break out between mongooses researchers have just found, with up to 30 animals on each side ‘arranged in battle lines’.
CLIMATE CHANGE AND ENVIRONMENT
Fights to the death, serious injury and the killing of litters are often the results of conflict between different groups of mongooses. While the interaction seems detrimental, researchers are uncovering the fact that there may be benefits. With support from the EU, the SOCDEV (Social development and life history evolution in cooperative mammals: an integrated approach) project is gaining insight into the dynamics of conflict among animals that are gregarious and their results are throwing up some surprises.
Professor Michael Cant of the University of Exeter, who leads the long-term study of banded mongooses in Uganda, says, ‘Intergroup conflict can be very intense in social animals but has really only been studied in depth in humans and chimpanzees before now.’
He explains that the fighting is costly to both individuals and groups, ‘Individuals are more likely to die and litters are less likely to survive to emergence if their group is involved in an aggressive encounter with a rival.’ However, while young mongooses are vulnerable to attack during fights, the project also found that pregnant females are significantly less likely to abort their litter if their group was involved in a fight.
While these findings may seem counter-intuitive, researchers posit that the reason might be the need to preserve numbers in the face of a lethal attack. Unborn litters may be seen as particularly valuable during periods of conflict with rival groups. ‘Pregnant females could be finding some way to maintain their pregnancy, perhaps to offset mortality from fighting and make their group bigger and more competitive in the future,’ Professor Cant explains in the journal 'Animal Behaviour'.
A further benefit might be the opportunity to mate with individuals from another group. Mating takes place during the attacks and as mongooses rarely stray beyond their immediate circle, these events provide a chance to widen the gene pool.
Broader application of new discoveries
While group fighting has been studied in pan troglodytes, namely chimpanzees, the lack of information on the causes and consequences of group aggression has set back understanding on what role intergroup conflict plays. SOCDEV aims to help address this information deficit.
There is great variation in the cooperative behaviour between individuals of the same sex, age and status. While studies of lab animals indicate this could be due to early life influences on development, little is known about the function and mechanism of these developmental effects in wild mammals, or whether these effects are adaptive.
The project is using large-scale field experiments to measure developmental impacts on offspring growth, stress physiology, cooperation, health, cognition and other factors. Findings arising from the research could reveal truths about social evolution in other cooperative mammals and may even clarify aspects of human dynamics. As Professor Cant explains, ‘Establishing the consequences of intergroup conflict in cooperative species can shed light on patterns of conflict and cooperation within groups and, in turn, facilitate our understanding of social evolution.’