Measuring Personality in Wild Small Mammals: A Review of Methods and Proposal for a Standardised Approach

Background: In recent years, the study of animal personality has gained significant attention in ecology and evolutionary biology. Small mammals are one of the most frequently studied mammalian taxa in this field, and their personality significantly impacts ecological outcomes. However, a review focused on the materials and methods to study wild small mammal personality is lacking. Aims: To address this gap, we aim to (1) identify the most consistent assays for measuring specific personality traits in wild species and (2) propose a standardised experimental design, detailing optimal arena size, shape and material, as well as standardised testing conditions and experimental procedures and highlighting critical aspects which require validation. Moreover, we (3) report a clear interpretation of the most commonly measured behavioural traits and the methods employed for their analysis. Material and Methods: Our review synthesises findings from 133 articles covering 54 species in a variety of habitats, ranging from the Canadian boreal forests to the semi-desert regions of South Africa. We found a concerning lack of standardisation in research methodologies, especially for key features such as the shape and size of arenas for behavioural assays and test duration. We observed considerable variability in how behavioural traits were interpreted. Nevertheless, we identified a suite of tests and interpretations of behaviours that allow for efficient processing of animals and produce consistent results in both field and laboratory settings. Conclusion: We conclude with five recommendations for a standardised approach to enhance the comparability of results and advance the field of wild small mammal personality research.