Post-copulatory guarding strategies in the non-territorial dragonfly Sympetrum sanguineum (Mu¨ller) (Odonata: Libellulidae)

Abstract

Reproductive behaviour, particularly mate-guarding strategies, of male Sympetrum sanguineum (Mu¨ller) was studied at Quy Poors Fen, Cambridgeshire, during 1984 and 1985. Two mate-guarding strategies used by males were identified. All pairs started oviposition while in the tandem or contactguarded formation; some pairs remained in tandem for the whole oviposition bout (termed ‘tandem only’ pairs), while the remainder separated before completion of the bout and the male continued to guard by a non-contact strategy (‘non-contact’ pairs). The switch in male guarding behaviour was related to the amount of interference from other males experienced during the early stages of tandem oviposition. Pairs employing the non-contact strategy had longer oviposition bouts than pairs using the tandem only strategy, but did not differ in the total number of egg-laying dips. Female dip rate was higher during the tandem than the non-contact phase of an oviposition bout. Females flick their abdomen while flying to aid egg release, and faster dip rates result in an increase in egg release rate. It is suggested that ovipositing females and tandem pairs are much more vulnerable to predation by larger odonates than lone males are, and therefore that male S. sanguineum adaptively switch between guarding strategies to balance the risk of losing their female to a rival male with the energetic and survival costs associated with tandem flight.