New research out of the University of Exeter (UE) in England makes a day in the life of a banded mongoose sound like an episode of the TV show, Vikings. Turns out the little critters engage in some pretty serious gang-like behavior that leads to death, sex between enemies, and an odd life-preserving side effect.
While cooperative and competitive behavior has been well documented in humans and chimps, the researchers say studies looking at such dynamics in other animals has thus far been poor.
For their research, they studied 43 social groups of banded mongooses living in Uganda over the course of about 16 years. Some mongooses were tagged with special color-coded collars, others were fitted with VHF radio collars and still others had special shave patterns applied to their fur. Those with the patterns were regularly trapped to maintain the unique looks, and those mongooses were also trained to step on a scale. Researchers visited the colonies every 1-3 days during typical weeks and every day when the females were breeding. During the time of the study they witnessed aggressive intergroup interactions a total of 570 times.
And those interactions were quite something.
"These fights are very chaotic, with 20 or 30 mongooses on each side arranged in battle lines," said lead author Faye Thompson, of the UE's Centre for Ecology and Conservation. "They all rush forward and fighting breaks out, with some individuals chasing each other into bushes – but at the same time males and females from opposing groups will sometimes mate with each other. 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."
The researchers also pointed out that the violent interactions typically start with a war-cry-like screech and that evenly-matched groups were more likely to battle than in cases where one group was outmatched by another, which usually led to the smaller group fleeing.
The researchers were able to ascertain that two major factors contributed to fights on any given day: high population densities and low rainfall – both conditions that meant groups of mongooses were competing for limited resources. They also determined that the intergroup interactions were higher when females in the group were in oestrus. Additionally, they postulate that the sexual encounters between members of different groups during the conflicts is a way to avoid inbreeding.
One of the more puzzling observations from the study is the fact that if female mongooses were involved in an aggressive intergroup interactions while they were pregnant, the rate at which they aborted their litters actually dropped.
One theory as to why this may be is that abortions are higher when female mongooses are evicted from their social group. During periods of conflict, this eviction process may go down to make up for the fact that the group suffers loss of life during the fights, especially among young members of the group.
The researchers also believe that the intensity with which groups of mongooses regularly battle helps build unity within groups. "Our results suggest that fighting between groups is one of the major forces promoting solidarity and cooperation within groups in these highly social mammals," said UE professor Michael Cant who lead the long-term study of the Ugandan mongooses.
The study has been published in the journal Animal Behaviour.
Source: University of Exeter