Causes and Consequences of Individual Variation
20 Pages Posted: 27 Apr 2009 Last revised: 18 May 2010
Date Written: April 27, 2009
No two individuals are alike. Even individuals of the same sex, age, size and social background tend to differ consistently in temperament, motivation, cognition and behaviour. In humans, such consistent differences are typically referred to as ‘personalities’. As every pet owner or farmer knows, dogs, cats, cows, sheep or canaries also have a well-developed ‘individuality’. In other words, animals also differ systematically in the way they cope with their environment. Indeed, ‘animal personalities’ (also called behavioural syndromes, temperament, or coping styles) have been described in a huge variety of (more than 300) species, ranging from spiders to bumblebees, from octopuses to sticklebacks, and from mice to monkeys (e.g., Clark & Ehlinger 1987, Digman 1990, Gosling 2001, Sih et al. 2004a). Examples abound. Birds of a similar phenotype differ consistently in the way they explore their environment and these differences are associated with, for example, differences in boldness and aggressiveness (Groothuis & Carere 2005). Rodents as mice and rats differ consistently in the way they deal with environmental challenges and such differences encompass differences in social tolerance, aggressiveness, cooperative breeding and even nest-building behaviour (Koolhaas et al. 1999).
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