Anti-predator strategies in oviposition site selection of Pyrrhosoma nymphula (Zygoptera: Odonata).

Selection of sites for oviposition when the risk of predation by green frogs was variable studied in tandems of the damselfly Pyrrhosoma nymphula. In the absence of predators the number of tandems landing increased with the size of the oviposition site and with the number of pairs already present. Pairs approaching an oviposition site landed promptly and preferred locations near other ovipositing pairs. Pairs which had landed near others left the landing site and flew to another water plant after a shorter period than those landing alone. They stayed in groups for only 16.5% of the total duration of stay at the oviposition site. With predators present fewer tandems landed. There was no relationship between the landing site of solitary tandems and the locations of the perching frogs. Pairs landing in groups were disturbed by frogs after a shorter period than pairs landing alone. Damselfly aggregation did not affect the predation success of the frogs, but the predation risk to individual tandem pairs was reduced.