Behavioral responses to fish kairomones and autotomy in a damselfly

The threat-sensitivity hypothesis predicts that prey species assess and adjust their behavior in accordance with the magnitude of the threat posed by a predator. A largely overlooked characteristic of a prey that will affect its sensitivity to predators is its history of autotomy. We studied threat-sensitive behavior to fish kairomones in larvae of Ischnura elegans damselflies, which had undergone autotomy, from a fishpond and from a fishless pond. In agreement with their higher perceived risk, larvae from the fishpond showed fewer rigid abdomen bends, foraged less and walked more slowly than larvae from the fishless pond. In line with their higher vulnerability to predators, larvae without lamellae spent less time foraging than larvae with lamellae. There was a decrease in swimming activity in the presence of fish kairomones except for larvae with lamellae from the fishless pond. This may reflect differences in vulnerability of larvae without lamellae between pond types. Such context-dependent responses in activity to kairomones should be kept in mind when evaluating the ability of a prey to recognize kairomones.