Browsing by Author "Allan, Bridie J. M."
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- At odds with the group: Changes in lateralization and escape performance reveal conformity and conflict in fish schoolsPublication . Chivers, Douglas P.; McCormick, Mark Ian; Allan, Bridie J. M.; Mitchell, Matthew David; Gonçalves, Emanuel João; Bryshun, Reid; Ferrari, Maud C.O.Many vertebrates are known to show behavioural lateralization, whereby they differentially use one side of their body or either of their bilateral organs or limbs. Behavioural lateralization often manifests in a turning bias in fishes, with some individuals showing a left bias and others a right bias. Such biases could be the source of considerable conflict in fish schools given that there may be considerable social pressure to conform to the group to maintain effective group evasion. Here, we show that predation pressure is a major determinant of the degree of lateralization, both in a relative and absolute sense, in yellow-and-blueback fusiliers (Caesio teres), a schooling fish common on coral reefs. Wild-caught fish showed a bias for right turning. When predation pressure was experimentally elevated or relaxed, the strength of lateralization changed. Higher predation pressure resulted in an increase in the strength of lateralization. Individuals that exhibited the same turning bias as the majority of individuals in their group had improved escape performance compared with individuals that were at odds with the group. Moreover, individuals that were right-biased had improved escape performance, compared with left-biased ones. Plasticity in lateralization might be an important evolutionary consequence of the way gregarious species respond to predators owing to the probable costs associated with this behaviour.
- Daily variation in behavioural lateralization is linked to predation stress in a coral reef fishPublication . Ferrari, Maud C.O.; McCormick, Mark Ian; Mitchell, Matthew David .; Allan, Bridie J. M.; Gonçalves, Emanuel João; Chivers, Douglas P.Behavioural lateralization, the preferential use of one side of the body or one of the limbs, is a trait common in vertebrates, and is often expressed as a turning bias in fishes. Recent studies have demonstrated considerable plasticity in lateralization, inferring the role of predation pressure as a key driver of this plasticity over short periods (i.e. days). Such plasticity may be expected if predator pressure is highly variable through space and time and can provide prey with a distinct advantage.We know that increased turning bias is linked with better escape performance, but we do not know the extent to which prey can adjust this trait to match temporal variation in risk. Here we trained juvenile Ambon damselfish to recognize different temporal patterns of risk throughout the day and asked whether their degree of lateralization changed according to this pattern. Damselfish that were taught that midday was risky showed a stronger turning bias at midday than in the evening, whereas damselfish that were taught that evening was risky showed a stronger turning bias in the evening than at midday. Subsequently, we found that fish exposed to cortisol expressed a greater degree of turning bias. Our results suggest that predation stress may be a key factor determining the degree of behavioural lateralization in vertebrates.