The Evolution of Animal Personality Variation Caitlin R Kight, University of Exeter, Cornwall Campus, Penryn, UK Morgan David, University of Exeter, Cornwall Campus, Penryn, UK Sasha RX Dall, University of Exeter, Cornwall Campus, Penryn, UK In many species of animals individual behaviour differs, yet is consistent over time and in an array of different environments; in other words, these animals display ‘personality’ variation. This may emerge not by chance, but, instead, is shaped by selective processes favouring individuals who display a differentiated behavioural phenotype. Indeed, personalities are known to affect important activities such as resource acquisition, survival and reproduction – which, cumulatively, impact an indi- vidual’s fitness. We currently lack the insights and tech- nology needed to fully characterise the genetics and physiology of most ecologically relevant behaviour; how- ever, much can be gained by adopting an adaptive approach to consider the evolutionary processes that might have driven the emergence and maintenance of stable behavioural variation. Such an exercise will allow us to develop a priori hypotheses about the mechanisms underlying the behaviour, and to conduct powerful empirical studies examining how individualised behav- iour impacts the life histories of a variety of species. Introduction For anyone who spends time watching animals, there is often a strong sense that, even within otherwise uniform populations of the same species, individuals differ pre- dictably in their behaviour. Indeed, it is becoming increasingly evident that such stable interindividual vari- ation – often referred to as ‘coping styles’ (Koolhaas et al., 1999), ‘temperament’ (Re´ale et al., 2000), ‘behavioural syndromes’ (Sih et al., 2004) and, of course, ‘animal personality’ (Schuett et al., 2010) – is widely distributed across the animal kingdom (Smith and Blumstein, 2008). Prompted by Wilson’s (1998) call for an evolutionarily motivated approach to studying biological variation at this scale, behavioural ecologists have recently put substantial research effort into developing this broad understanding of individual variation (for a recent review, see Bell et al., 2009). One essential component of this work, and the main focus of this article, is an evaluation of the evolutionary processes that may underlie this apparently common feature of animal populations and individual behaviour. See also: Animal Personality What is animal personality? At some level, it is intuitively obvious what personality is. Given our sociobiology, we, as humans, effortlessly cue in on individuality and individual behaviour patterns. This is reflected in the centrality of personality studies in treat- ments of human behaviour in the social sciences and humanities (Nettle, 2006). Nevertheless, psychological definitions of personality range from the vaguely broad (‘individual differences within species’; Gosling and John, 1999) to the idiosyncratically human-specific (‘those char- acteristics of individuals that describe and account for consistent patterns of feeling, thinking and behaving’; Pervin and John, 1997). However, these extremes are of limited value when considering patterns of individual variation in an evolutionary and ecological context. Thus, further elucidation is clearly required. There are several types of phenomena that should be included within the scope of animal personality studies in order to elucidate their evolutionary function. First and foremost, investigators must consider behavioural vari- ation amongst individuals within otherwise homogenous populations or groups of the same species. Crucially, however, researchers must also consider the patterns of behaviour that individuals exhibit over some portion of their lifetimes and/or across the different biological con- texts they face (e.g. foraging, mating, socialising, etc.) as a hallmark of personality is the relative consistency of Advanced article Article Contents . Introduction . What is animal personality? . Why is animal personality interesting from an evolutionary perspective? . Factors selecting for interindividual variation within populations . Factors selecting for individual behavioural specialisation . Conclusions Online posting date: 15 th May 2013 eLS subject area: Evolution & Diversity of Life How to cite: Kight, Caitlin R; David, Morgan; and Dall, Sasha RX (May 2013) The Evolution of Animal Personality Variation. In: eLS. John Wiley & Sons, Ltd: Chichester. DOI: 10.1002/9780470015902.a0024662 eLS & 2013, John Wiley & Sons, Ltd. www.els.net 1