Personality tips the scale: how individual differences in exploration shape behavioural and hormonal adjustment to different environments

Individuals show consistent differences in their behaviour across time and/or context, usually referred to as animal personality in behavioural ecology. These inter-individual differences raised the question if animals of different personalities also vary in how they adjust to certain environmental conditions. In the present study, we aimed to investigate personality-dependent differences to different environmental conditions. By means of two distinct experiments, Lister Hooded rats ( Rattus norvegicus f. domestica ) were characterised regarding their level of exploration and exposed to an environment with a predictable versus an unpredictable food availability (experiment 1) or to an environment with a social partner of matching versus mismatching personality (experiment 2). To assess behavioural differences between individuals of varying exploration levels, the home cage behaviour of the animals was monitored and two tests for measuring anxiety-like behaviour were conducted. Furthermore, concentrations of baseline faecal corticosterone metabolites were determined to record hypothalamic–pituitary–adrenocortical activity repeatedly. The characterisation showed consistent inter-individual differences in exploration levels in both experiments. While personality, environment and the interaction of both did not affect faecal corticosterone metabolite concentrations in neither of the experiments, several behavioural differences between individuals of varying exploration levels were detected in the home cage and in the tests. Most interestingly, interactions between personality and environment were found, pointing towards a better behavioural adjustment of highly explorative animals to predictable conditions. Therefore, the results emphasise the existence of context-specific personality-dependent behavioural patterns. Moreover, personality-dependent and environment-dependent differences in welfare-associated measures were reported. More specifically, a predictable food availability was associated with more affiliative and less agonistic behaviour, whilst a matched social partner was linked to increased locomotor activity in one of the behaviour tests. Additionally, restructuring of the social group was reported to increase faecal corticosterone metabolites. Thus, the study does not only highlight the importance of integrating personality into eco-evolutionary perspectives on adjustment processes but also points towards relevant aspects for animal welfare endeavours.