BLBK374-07 BLBK374-Brown May 13, 2011 17:9 Copyeditor’s Name: Trim: 244mm X 172mm Char Count= Chapter 7 Personality Traits and Behaviour Sergey Budaev and Culum Brown 7.1 Introduction Individual differences in animal behaviour have been attracting the interest of researchers at least from the time of Darwin (Slater 1981; Caro & Bateson 1986; Clark & Ehlinger 1987; Sih et al. 2004; R´ eale et al. 2007). Such an interest is justified because individual differences represent the raw material of natural selection and evolution, the main cornerstone of modern biology. Furthermore, the individual is, after all, the main unit of selection (Maynard Smith 1982). Within-population variation in alternative mating strategies, foraging tactics and other observed behaviours are now widely accepted in behavioural and ecological literature. Recent investigations, however, have revealed individual differences in behavioural traits that are consistent over time and across situations. Often, such variability cannot be easily described using observable behaviour and involves inference and interpretation in terms of internal physiological or psychological mechanisms such as fearfulness or aggressiveness. Essentially, such variation represents an analogue of human personality. Some people may accept personality in ‘higher’ animals such as primates or even in dogs, but seem to deny it in ‘lower’ species (such as fish) due to the underlying fear of anthropomorphism. Ironically, this is an example of anthropocentric thinking in terms of a ‘Scala Naturae’, which has long since been discredited (Hodos & Campbell 1991). Personality traits have now been identified in a variety of animals and in fact are actively manipulated by people working closely with them (e.g. police horses, guide dogs and domestic animals generally). A meta- analysis of the available animal literature suggests that about 35% of behavioural variability of single behavioural patterns can be ascribed to individuals (Bell et al. 2009). While there is still debate about the degree to which individual differences in behaviour are consistent across different situations (see Wilson et al. 1994; Coleman & Wilson 1998; Bell 2005; Wilson & Stevens 2005; Dingemanse et al. 2007), there is no doubt that consistency of behaviour exists within many situations. Fishes have rapidly become one of the most widely studied animals with respect to per- sonality largely because of the utility of housing and breeding them in the laboratory, but Fish Cognition and Behavior, Second Edition. Edited by Culum Brown, Kevin Laland and Jens Krause. C  2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.