Temporally consistent behavioural variation between wild ant colonies is robust to strong seasonal and thermal variation.

Individuals of the same species represent the greatest competitors to one another as they have the same demands in terms of food and habitat. Therefore, these overlapping niches might favour interindividual trait variation by promoting niche differentiation. An ecologically important aspect of trait variation is behaviour. Behavioural differences between conspecific individuals that are consistent across time are defined as 'animal personality'. Whereas animal personality traits have been described under laboratory conditions in many insects, including ants, knowledge about consistent behavioural variation in the field is scarce. Here, we investigated intercolonial behavioural variation in the ant species Lasius niger in the field. We used standardized behavioural assays for exploration, aggression, responses to chemical cues of con- and allospecific ants, the tendency to forage at honey and the foraging activity at the nest. Each assay was repeated five times over the course of the season. We found temporally consistent differences between colonies for exploration and aggression as well as for foraging activity, but not for responses to chemical cues. This consistency is the more remarkable as nearly all traits showed strong seasonal and temperature effects. This suggests that traits can be plastic and consistent at the same time. Our study shows that despite variable abiotic and biotic conditions, temporally consistent animal personality traits can be detected in the field underlining their importance in understanding ecological interactions and intraspecific coexistence. • Ant colonies differ in behavioural traits. • These include exploration, aggressiveness and foraging activity. • The differences are consistent and reproducible even in the field. • They are characteristic of colonies rather than individual workers. • Despite this consistency, behaviour is strongly affected by temperature and season. [ABSTRACT FROM AUTHOR]