Repeatability in boldness and aggression among wild zebrafish (Danio rerio) from two differing predation and flow regimes.

Although flexibility in behavior is adaptive, this flexibility is limited, and the extent of variation and consistency of a trait could depend on the environment. In this study, we investigated repeatability in risk-taking during feeding among individuals and agonistic interactions among dyads of wild zebrafish, Danio rerio, collected from two habitats that differed in predation and flow regimes. We measured boldness as the latency to emerge from a shelter and feed in the presence of predators. We tested this for each individual from the two populations repeatedly across seven trials. We assessed aggression by subjecting size- and sex-matched pairs of fish to dyadic contests repeatedly across seven trials. Individuals from the high-predation stream population were bolder than individuals from the low-predation stagnant water population. Males were bolder than females, and in the low-predation population, larger individuals took greater risks to feed than smaller individuals. The high-predation stream population showed lower inter- and intraindividual variation in boldness than the low-predation stagnant water population. Further, both populations showed significant repeatability in risk-taking during feeding. The high-predation stream habitat fish were more aggressive than low-predation stagnant-water fish. Male dyads from the low-predation stagnant-water population were significantly more aggressive than female dyads. Most fish from the low-predation stagnant water population did not show aggressive behavior, resulting in low between-dyad but high within-dyad variation in aggression. The difference in behavioral responses between the populations and consistency in these traits within individuals is discussed in the light of confounding role of ecological and state-dependent factors. (PsycINFO Database Record (c) 2018 APA, all rights reserved).