Effects of predators and injury over different time scales in the damselfly Ischnura posita (Odonata: Coenagrionidae)

Abstract

Sublethal appendage injury or loss has been shown to alter many behaviors of animals, including foraging and predation avoidance. But most studies of this phenomenon to date have been short-term in scope, and longer term studies may produce different results as seen in some studies on predator effects. Larval damselflies routinely autotomize their caudal lamellae and encounter predators, making them ideal for comparisons of short-term and longer term effects of appendage loss and predator exposure. In this study, I examined activity and foraging of larval Ischnura posita (Hagen) (Odonata: Coenagrionidae), testing for effects of lamella loss and predator cues both in the short term (1 h) and the longer term (8 d). I predicted that both predators and injury would decrease activity and foraging for a short time and that these effects would diminish over time. Results indicated that only the most severe injuries affected foraging, delaying first prey capture when no predator was present; but injury did not affect total prey caught. In the 1-h experiment, damselflies had lower activity in the presence of predator cues, with no effect of injury, whereas the 8-day experiment showed no effect of predator cues on activity. I did not find a major effect of injury or predator cues on activity or foraging of larval damselflies; no effects were detectable over the entire 8-d study. I conclude that the ecological implications of such injuries in nature may often be negligible. © 2011 Entomological Society of America.