Influence of predator presence and prey density on behavior and growth of damselfly larvae (Ischnura elegans) (Odonata : Zygoptera)

Foraging behavior is often determined by the conflicting benefits of energy gain and the risk of mortality from predation or other causes. Theory pred icts that animals should have lower activity levels when either the risk of predation or the availability of resources in the environment is high. We investigated the adjustment of the behavior of I, elegans larvae to predato r presence (Anax imperator) and prey density (Daphnia sp.) and their intera ction in a completely crossed factorial experiment in the lab and the effec t of behavior oil growth. The foraging activity of the I. elegans larvae wa s significantly reduced in the presence of a free-swimming predator but not a caged predator. Abdominal movements were significantly reduced at a low prey density, Growth was significantly reduced by the presence of a free sw imming predator and low prey densities. These results provide evidence that these damselfly larvae adjust their behavior to the presence of predators to increase their survival at the expense of reduced growth and development .