In situ examination of boldness–shyness traits in the tropical poeciliid, Brachyraphis episcopi

Abstract

Explaining consistent variation in the behaviour of individuals in terms of personality differences is one of the cornerstones of understanding human behaviour but is seldom discussed in behavioural ecology for fear of invoking anthropomorphism. Recently, however, interest has begun to focus on identifying personality traits in animals and examining their possible evolutionary consequences. One major axis used to define personality traits is the shyness-boldness continuum. We examined boldness in an in situ experiment using fish from eight populations of the poeciliid Brachyraphis episcopi (also referred to as Brachyrhaphis episcopi). Fish from high-and low-predation regions within four streams that run independently into the Panama Canal were tested. Boldness scores were strongly influenced by standard length and the relative level of predation pressure in the rivers. In all four rivers, fish from high-predation areas were bolder than those from low-predation areas. Fish became increasingly shy as they grew. Animals are expected to titrate energy intake closely with predation risk and hundreds of studies support this notion (reviewed in Lima 1998). For example, when a risky patch had four times the amount of food available than a low-risk patch, fish accepted the higher risk in return for a higher foraging reward (Pitcher et al. 1988). Not all individuals in a population solve the problem in the same way, however. In laboratory assays of foraging behaviour under predation risk, there is a continuum of responses within a population of prey species, from complete recklessness to complete predator avoidance (Fraser & Huntingford 1986). These behavioural extremes correspond closely to the shyness-boldness spectrum, recognizable psychological states that exist in a diverse suite of taxa, from crustaceans to humans (Wilson et al. 1994; Gosling 2001). Although many studies have concentrated on the heritability of individual differences in temperament (Goddard & Bilharz 1985), this range of responses is also determined by life experiences (van Gestel & van Broeckhoven 2003), and, as such, should be influenced by environmental variables during ontogeny. While the two mechanisms are by no means mutually exclusive, the manner in which the environment shapes and maintains shyness-boldness traits over both evolutionary and ontogenetic timeframes has received little attention from behavioural ecologists. Comparative analyses are frequently used to address potential differences in animal behaviour caused by variable exposure to selection pressures that result from the occupation of different environments (Kamil & Balda 1990). Testing populations of the same species that occupy different habitats allows us to examine how the environment affects the determination of personality traits while minimizing the possible confounds of phylogeny.

Individual quality and personality: bolder males are less fecund in the hermit crabPagurus bernhardus

“…These decapod crustaceans occupy empty gastropod shells, and when threatened, they withdraw rapidly into them before slowly re-emerging. The duration of this startle response is directly analogous to that shown by other animals which retreat into a refuge upon being disturbed and usually described as 'boldness' (see [29,38,42] for examples). Here, we first look at boldness in relation to investment in haemocyanin, the respiratory pigment of crustaceans, which varies among individuals and contributes to their capacity for demanding aerobic activity [43].…”

Patterns of predator neophobia: a meta-analytic review

“…Often, some individuals will show weak or even no neophobic responses (e.g. [27,28]). However, observations of high levels of neophobia are repeatable and can correlate across contexts (e.g.…”

Cognitive ability is heritable and predicts the success of an alternative mating tactic

“…The assay measured time to emerge from a refuge (for simplicity, hereafter referred to as 'emergence time'), estimated as the time taken for an individual to emerge from shelter in a novel environment [23].…”

“…To control for the potentially confounding effects of variation in 'shyness -boldness' sensu [23], a behavioural assay was performed. The assay measured time to emerge from a refuge (for simplicity, hereafter referred to as 'emergence time'), estimated as the time taken for an individual to emerge from shelter in a novel environment [23].…”