In a crisis, Africa’s smallest carnivores can rely on those around them. A new study shows that when faced with potential violence from rival factions, dwarf mongoose (Helogale parvula) groupmates pull together and act more co-operatively.
In field experiments, researchers from the UK’s University of Bristol observed changes in a range of within-group behaviours.
“Much is known about the behaviour that occurs when groups of the same species actually interact with one another,” says lead author Amy Morris-Drake.
“However, we have shown that the threat of between-group battles can lead to increases in within-group cooperation, including greater grooming of groupmates and contributions to sentinel duty – acting as a raised guard.”
Co-author Andy Radford adds that experimental tests of the consequences of out-group conflict are extremely rare, especially on wild animals.
“By working with groups of dwarf mongooses habituated to our close presence, we could collect detailed observations and conduct experimental manipulations in natural conditions.”
The researchers simulating territorial intrusions in a wild population of dwarf mongooses in a private game reserve in the Limpopo Province of South Africa.
Using call playbacks and faecal presentations they created the impression that trouble-makers had crossed the border into a group’s land, then observed the behaviour of the resident group after it had interacted with the cues of rivals.
“Individuals groomed one another more and foraged closer together, potentially due to higher anxiety levels; their increase in sentinel behaviour was likely an attempt to gather more information about the threat,” Radford say.
The influence of an out-group threat was observed to last at least an hour. Individuals of different dominance status and sex responded similarly, potentially because all group members suffer costs if a contest with rivals is lost.
“Investigations of longer-term responses, beyond the immediate effect of elevated anxiety, are crucial if we are to understand fully the range of costs and benefits at play and will help to shed light on the relationship between intergroup conflict and its suggested role in the evolution of cooperation,” the authors write.
It is often suggested that one reason for the high levels of co-operation in human societies is the need to stand together in times of war. Morris-Drake and colleagues suggest that their study demonstrates the basis for a similar link in other animals.
The findings are published in the journal Behavioural Ecology.
Nick Carne is the editor of Cosmos Online and editorial manager for The Royal Institution of Australia.
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