Violent evictions target familial females in mongoose groups
To look at one, you wouldn't necessarily think that a banded mongoose was a very fierce critter. However, researchers at the University of Exeter have shown that the animals engage in some pretty significant warlike behavior that starts with a screech and can easily end with death. Now, the same researchers have uncovered a different not-so-nice behavior exhibited by the banded mongoose: When females are kicked out of the group, close family members are often the first to go.
Unlike other mongoose species, the banded mongoose lives in socially-oriented colonies with complex structures. This means that there are dominant males in the colony who want to increase the chances that their offspring will thrive. So to eliminate the number of females who can produce offspring that may not belong to them, the dominant males will conduct mass evictions of females, often in a violent way that can lead to injury and sometimes death.
In a new study published in the Proceedings of the National Academy of Sciences, the Exeter researchers figured out that the first females to go are often closely related to the dominant males doing the evicting. They've determined that this is because related females often fight back the least, as they're concerned about inflicting damage on a fellow family member – a concern clearly not shared by the males.
"Targeting close relatives for eviction like this is the opposite of what we would expect social animals to do," said lead author Dr Faye Thompson, of the Centre for Ecology and Conservation on the University of Exeter's Penryn Campus in Cornwall. "Our research shows that related females submit more easily because they are more sensitive to the costs they inflict on their relatives by fighting to stay in the group. As dominant banded mongooses need to evict rival females to reduce competition for their own offspring, their best strategy is to target close relatives."
Interestingly, the researchers also discovered that, while the behavior seems harsh, the dominant mongooses at least won't target other colony-mates that are not able to defend themselves.
"It seems that aggressive animals can anticipate the possibility of resistance and change their behavior accordingly," said senior author Rufus Johnstone of the University of Cambridge. "This appears to have a big effect on the way they treat relatives and non-relatives, and suggests that latent threats might exert an important influence on social behaviour more generally."
The finding comes from an 18-year study of banded mongooses in Uganda and is funded by the Natural Environment Research Council and the European Research Council.
"We've long wondered why some individuals are marked out for violent attack and eviction, whereas others are permitted to stay," said Professor Michael Cant, of the University of Exeter, who has been leading the research. "Our new study shows that a crucial determinant is whether victims can put up a fight, and predicts that closer kinship sometimes goes hand in hand with more intense aggression."
Source: University of Exeter