The effects of male size on dragonfly perch selection and competitive outcomes in Southeastern Virginia

Background/Question/Methods

Many species of dragonflies perch within territories where they catch prey, mate with females and chase off rival males. Different species select either tall or short emergent vegetation for perching. In the present study we examined whether dragonfly size influenced perch height choice on tall (90cm) or short (30cm) artificial bamboo perches at four lakes in Southeastern Virginia over three years. We also recorded whether the outcomes of contests over perches were related to dragonfly size.

Results/Conclusions

Perch height selection was not related to dragonfly size. One small species (Celithemis eponina) and two large species (Libellula needhami, and L. incesta) routinely used tall perches while one medium-sized species (Erythemis simplicicollis) chose short  perches. Also, one large species (Brachymesia gravida) and one small species (Pachydiplax longipennis) used both tall and short perches. Perching dragonflies were often displaced from perches by conspecific or heterospecific males, but dragonfly size had no effect on which male won or lost the contest over perches. The small P. longipennis was competitively superior to the large species L. needhami, and L. incesta, but the medium-sized E. simplicicollis outcompeted P. longipennis. Dragonflies may partition resources through perch height choices. Therefore wetland management programs should consider maintaining a variety of emergent vegetation heights to support dragonfly species diversity.