Individual deviation from behavioural correlations: a simple approach to study the evolution of behavioural syndromes

Abstract

The study of correlations between different behaviours in a population-referred to as behavioural syndromes-has begun to flourish during recent years. However, the evolutionary mechanisms that cause behavioural traits to vary non-independently from each other are still poorly understood. Here, we bring behavioural syndromes into a new perspective, in which the phenomenon is regarded at the individual level and on a continuous scale instead of as a population-level presence/absence trait. As the correlation between behaviours is never perfect (i.e. r < 1), individuals are likely to vary in how consistently they behave. Therefore, we can predict that if behavioural syndromes at the population level are results of natural selection, the consistency in a suite of behaviours-and not the behavioural configuration per se-should be heritable and involve fitness advantages at the individual level. We define a variable that describes the individual deviation from the hypothetical perfect correlation predicted by the syndrome. The use of such a variable depicting the consistency of behaviours of individuals allows us to make solid evolutionary inferences about correlated behaviours from patterns of individual instead of population variation. We suggest that, by adopting the concept of syndrome deviation, understanding the evolution of behavioural syndromes and, in particular, testing competing evolutionary hypotheses about the origin of behavioural syndromes becomes possible in a more rigorous manner than before. While correlations between different behaviours were described already a good while ago (Huntingford 1976), ethologists and behavioural ecologists continued to study behavioural traits (e.g. aggression, foraging) and ecological contexts (e.g. mating vs. non-mating seasons) in isolation from each other assuming case-by-case individual optimisation. However, the interest has recently turned towards analysing behavioural traits across different contexts (e.g. aggression towards competitors and own offspring) or analysing a suite of behavioural traits (e.g. aggression towards conspecifics and risk-taking in the presence of predators) together. When correlations across contexts and/ or behavioural traits exist, the resulting phenomenon bears a close resemblance to human personality (Gosling 2001). Such correlations are often referred to as 'behavioural

Male Courtship Pheromones Affect Female Behaviour in the Swordtail Characin (Corynopoma riisei)

“…Moreover, correlations between behaviours are common among individuals in many animals (e.g. Huntingford 1976;Herczeg & Garamszegi 2012). In the control females, we found a strong positive correlation between activity and stress which was disrupted by the stressor.…”

“…This may, in itself, be a stressful situation for the females of both treatments, and the interaction of the confined space with each treatment is unknown. Huntingford 1976;Herczeg & Garamszegi 2012). In addition, females are often highly aggressive towards courting males, at least initially (Nelson 1964;own observations).…”

No personality without experience? A test onRana dalmatinatadpoles

“…Further studies are needed to separate the effects of genes, environment and their interaction on animal personalities and behavioral syndromes. Possible solutions include using laboratory animals with known genetic background and testing for environmental effects on presence/absence/strength of behavioral consistency at the group-level (see Carere and Maestripieri 2013 for promising results obtained with laboratory rodents), or using individual-level estimates of behavioral consistency (e.g., Herczeg and Garamszegi 2012;Stamps et al 2012) and subject it to standard evolutionary testing (for recent examples, see Briffa 2013;Briffa et al 2013;Westneat et al 2014;Bridger et al 2015).…”

Great tits take greater risk toward humans and sparrowhawks in urban habitats than in forests

“…Risk‐taking toward humans is often suggested to correlate with other forms of risk‐taking behavior, such as aggressiveness (risk‐taking toward a conspecific opponent; Scales, Hyman, & Hughes, ; Myers & Hyman, ), neophobia and exploration (risk‐taking toward novel stimuli; Bókony, Kulcsár, Tóth, & Liker, ; Carrete & Tella, ), and anti‐predator behavior (risk‐taking toward non‐human predators; Bókony et al, ; Carrete & Tella, ; Myers & Hyman, ). Such phenotypic correlation across different situations is often called “behavioral syndrome” (Sih, Bell, & Johnson, ; Herczeg & Garamszegi, ; but see Dingemanse, Dochtermann, & Nakagawa, ). The correlation between responses to humans and responses to non‐human predators is often considered to be particularly strong, as it is frequently assumed that animals perceive humans as a type of predator (Beale & Monaghan, ; Frid & Dill, ).…”