Thermal stress increases activity and risk-taking behavior but not anxiety in a livebearing fish

Abstract

Characterizing the potential for, and mechanisms of, organismal response to environmental stress, particularly in the context of temperature, remains important for predicting effects of global change on natural populations. A number of studies have looked at changes in behavioral variation, focusing primarily on activity, boldness and aggression, while many behavioral traits have gone unexplored. In this study, I examine responses of a widespread neotropical livebearer, the barred killifish, to variation in water temperature. In addition to activity and boldness, I assayed variation in anxiety (measured as thigmotaxis – preference for edges) following a short-term exposure to thermal stress. Similar to other studies, elevated temperatures were associated with significant increases in activity and propensity for risk-taking behavior. There was no effect of thermal stress on anxiety, but males did have overall lower anxiety than females. An increase in activity and boldness may be a general response to thermal stress, even if competing hypotheses of the adaptive benefit remain unresolved. The insensitivity of thigmotaxis to thermal stress suggests that this measure of anxiety may be independent of variation along the shy-bold axis and therefore represent a useful measure for future studies of behavioral variation.