Shaping the antipredator strategy: flexibility, consistency, and behavioral correlations under varying predation threat

Recent ecological and evolutionary research emphasizes the importance of adaptive trait integration. For instance, antipredator defenses are built up of several morphological and behavioral components in many species, yet their functional relationships are still poorly documented. Using field-collected freshwater crustaceans Gammarus fossarum in a within-subject design, we investigated the flexibility and consistency of refuge use, photophobia, and exploration behavior as well as their associations, quantified both when predation risk was absent or artificially simulated. In agreement with the ``threat-sensitivity'' hypothesis, both refuge use and photophobia increased under predation risk, whereas exploration behavior did not vary. For all behaviors, individuals exhibited low but significant consistency between risk treatments. However, intraindividual variability did not vary with weight or between sexes. Finally, a positive relationship between photophobia and refuge use was observed only under predation risk in females, whereas it was found in both risk treatments in males. Our findings demonstrate that predation risk may promote behavioral flexibility and behavioral correlations, or syndromes, in wild populations, and call for an integrative study of antipredator mechanisms where the evolution of each dimension has to be examined in combination with all others. Additional phenotypic traits should be included in future studies to better characterize the multidimensionality of antipredator defense and the functional relationships among traits. The survival consequence of behavioral correlations between risk-sensitive traits also remains to be estimated in mortality selection experiments.