2026/02/24 by Josh J. Arbon, Amy Morris-Drake, Julie M. Kern +1 · 1 voice · 1 citation
Agricultural and Biological Sciences · Social Sciences · Psychology · #Animal Behavior and Reproduction #Evolutionary Game Theory and Cooperation #Primate Behavior and Ecology
paper · doi:10.1016/j.anbehav.2026.123474
Within-group aggression has well-established immediate effects on the contest-related behaviour of both participants and other group members (i.e. bystanders). However, we know far less about how within-group aggression influences behaviour not directly related to a contest and how cumulative information from contests can affect later behaviour. Moreover, it is unknown how any such behavioural changes are modified by the threat of intergroup contests, which are likely more costly and require a united response from groupmates, leaving an incomplete picture of how animals balance conflict at different scales. To test how individual and cooperative behaviours are affected by a general elevation in perceived within-group aggression, and how those behavioural responses change when there is an increase in the intergroup threat level, we ran a field experiment with groups of dwarf mongooses, Helogale parvula . Playback of simulated foraging displacements of subordinates by dominants led to bystanders avoiding close proximity with the seemingly aggressive individuals and reducing their cooperative sentinel contributions. The prospect of an intergroup contest (simulated by faecal and vocal presentations of a rival group) caused subordinates to return to close proximity with dominants, but sentinel contributions remained lower on days where elevated within-group aggression was simulated. This work highlights the potentially lasting effects of within-group aggression and how animals balance the threats of conflict from within and between groups. • Within-group aggression had broad effects on the behaviour of bystanders. • Bystanders distanced themselves from aggressors and reduced cooperative vigilance. • Increases in intergroup threat reset proximity between groupmates. • Vigilance measures remained impacted by aggression despite intergroup threat. • Conflict in groups can therefore impact both within- and between-group behaviour.