Behavioral responses to predation risk in brooding female amphipods (Gammarus pseudolimnaeus)

Abstract

Previous research has shown that brooding female amphipods (Gammarus pseudolimnaeus) are more likely than other adults to be eaten by vertebrate and invertebrate predators under restrictive laboratory conditions. Here, we investigate how the mobility of amphipods that differ in sex or reproductive status varies. Second, we investigate whether any such differences in mobility are associated with differences in predator avoidance behaviors. Male amphipods collected from the field had 18% higher maximum velocity and 44% higher average velocity than females. Non-brooding females had 33% higher maximum velocity than brooding females, but their average velocities were not significantly different. The average velocity of brooding females was negatively correlated with brood size. Brooding females were significantly more likely to aggregate and to seek cover when predator cues were present, whereas the responses of males and non-brooding females were more variable, as predicted by the trait compensation hypothesis. Behavioral plasticity in predator response behavior likely provides a mechanism for brooding females to mitigate predation risk during the period in which their mobility is impaired. These intraspecific differences in predator response may have important implications for stream community ecology and fisheries management.