Dwarf mongooses pre-emptively alter their behaviour relative to the threat posed by different rival groups.

Intergroup conflict is a potent evolutionary force across taxa, but little research has investigated how social animals pre-emptively change their behaviour in scenarios where contests with rivals are more likely. Moreover, the few studies examining this aspect of intergroup conflict fail to consider rival characteristics despite them determining contest outcomes and interaction costs, which define the threat level different groups pose. Here we show how non-human animals can tailor their anticipatory behaviour to the specific threat posed by rivals, using 10 years of detailed behavioural observations and GPS data. We demonstrate that dwarf mongooses (Helogale parvula) adjust their space use, information provisioning and resource defence dependent on the relative group size of neighbours to help them mitigate the threat from both well-matched competitors and more dangerous larger rivals. By contrast, behavioural differences between the core and edge of home ranges were more equivocal, highlighting the importance of considering rival characteristics rather than just spatial location as an indicator of threat level. Our results showcase how animals have evolved to be best prepared for a key part of their ecology, potential future contests, indicating abilities that allow them to survive and thrive in a landscape of intergroup conflict.