Trading off mortality risk against foraging effort in damselflies that differ in life cycle length

Life history theory predicts that size and age at emergence depend on the s lope and shape of the relationship between mortality rate and foraging effo rt. Given the high expected foraging effort in obligate univoltine species compared with semivoltine species we expected a low slope and an increase i n foraging effort in the presence of a predator for the former and the oppo site: pattern for the latter. We tested these predictions in two damselfly species of the univoltine genus Lestes, and the semivoltine genus Coenagrio n when confronted with perch. We determined for each of the four study spec ies the relationships between mortality rate and foraging effort at an indi vidual level. As expected by the different growth demands associated with d ifferences in life cycle length, both Lestes species had a higher foraging effort than the two Coenagrion species in the absence as well as in the pre sence of perch. As a result, lestids also suffered a higher mortality rate. The slope of the regression between mortality rate and foraging effort was , as predicted, lower for lestids than for coenagrionids, for one species p air. Despite this, and opposite to our prediction, the lestids decreased fo raging effort even more than coenagrionids in the presence of perch. We dis cuss these findings in the light of life history responses in species that differ in life cycle length.