Differences in social behaviour between group-living and solitary African striped mice, Rhabdomys pumilio

Abstract

Little is known about the extent to which solitary individuals differ in their social behaviour from group-living ones within the same species. Using the socially flexible African striped mouse, we tested through a series of dyadic encounters in a neutral arena whether group-living mice that later became solitary differed from their philopatric conspecifics. We compared philopatric and solitary mice both before and after dispersal. We predicted striped mice that became solitary would be more aggressive, less amicable and more investigative than individuals that remained group living, and would change their social behaviour after changing from group to solitary living in the same direction (becoming more aggressive, etc.). Dyadic encounters were conducted on 42 group-living individuals and 13 individuals that were first group living and later became solitary. Striped mice that became solitary showed higher levels of aggression and social investigation than their conspecifics that remained group living, differences that were already present before individuals dispersed. Dispersing striped mice showed a negative correlation between amicability and aggression towards opposite-sex individuals, which could be linked to sexual motivation. A second behavioural syndrome in the form of a positive correlation between aggression and social investigation towards same-sex individuals might have indicated that dispersing striped mice were ready to defend their own territory. Our study provides evidence that within the same population and at the same time, individuals that disperse and become solitary differ behaviourally from their group-living conspecifics even before dispersal, and further change their behaviour after dispersal in an evolutionarily adaptive way.