Revisiting the foundations of animal personality

Animal personality research is incredibly important, but at the same time faces constant criticisms over its methodological and theoretical foundations. These foundational problems undermine the progress of the field, its reputation, and its impact, and need to be addressed so that previous research can be understood clearly, and that future research can progress in a grounded and efficient way. This thesis addresses two concerns in the animal personality field: 1) a lack of developed theory of personality traits in animals, and 2) a lack of research informing basic methodological decisions. Chapter one develops a clear pathway for developing and testing trait theory in animals. An underdeveloped trait theory is the ultimate cause for most of the problems raised in recent reviews of the field. Learning from approaches used in human psychology and in phylogenetics, I describe a bottom up approach to develop the structure of animal personality in a species. This structure will both determine the appropriate number of personality traits and trait categories/dimensions, and determine which behaviours reflect each trait. Chapter two investigates the effect of acclimatisation on behaviour in two different populations of the guppy, Poecilia reticulata. I found that longer acclimatisation leads to more repeatable behaviour in an activity assay, and recommend that activity be measured in a familiar environment. For an emergence assay, individuals must be moved to an unfamiliar apparatus and cannot be acclimatised for long periods due to the nature of the starter box. Furthermore, acclimatisation periods are limited due to unideal starting conditions for the animal. I found that although intermediate acclimatisation time led to the highest behavioural repeatability, the emergence assay produced highly repeatable behaviour overall regardless of acclimatisation period. This suggests that the emergence assay generally generates robust behavioural responses. I recommend that researchers investigate acclimatisation times within their study population using their chosen behavioural assays prior to commencing research. Although further research is required to answer the criticisms of animal personality research, these chapters are each a step towards addressing two of the foundational issues in the field.