Effects of Prey Type, Prey Density and Predator Presence on Behaviour and Predation Risk in a Larval Damselfly

For many animals feeding efficiency trades off against predator avoidance. In laboratory experiments damselfly larvae (Coenagrion hastulatum) changed their behaviour both when a larval dragonfly predator (Aeshna juncea) was introduced, and in response to different prey treatments. The frequency of five «prey catching» behaviours was considerably lower in the presence of a predator when fast swimming Heterocope saliens copepods were used as prey, than, when sedentary Sida crystallina cladocerans were used. I interpret this prey effect as a result of the low encounter rate with Sida prey. The more «general» behaviours walk, abdomen wave, scratch and turn were performed less in the presence of the predator and both prey types. In contrast the behaviours rotate and swim were performed at higher frequencies in the presence of a predator