Demographics and behaviour of Heteragrion cooki, a forest damselfly endemic to Ecuador (Odonata)

Abstract

Damselflies adapted to forest habitats are expected to be negatively affected by the disturbance of riparian forests, due to the change in insolation when trees are cleared. In this paper, we compare survivorship and behaviour of two populations of Heteragrion cooki by means of mark-recapture methods and focal observations of adults. We found similar densities of males (but not of females) in both streams, and similar recapture rates, higher for males (50%) than for females (20%). Body size was also significantly different between populations, with smaller individuals in the shadiest stream. The analysis of daily survival rates indicated that in the shaded stream, males survived better than females, whereas in the sunnier stream survival was similar between sexes, but varied over time. Furthermore, in the sunny stream, body size was negatively correlated with survival. Males arrived earlier than females to the stream, with a maximum activity between 13 and 16 hours. They defended small patches of the stream, exhibiting high site fidelity and aggressive behaviour against conspecific males. Copulation, which was very rarely seen in the stream, lasted about six minutes. Pairs in tandem remained for an average of 45 minutes laying eggs on roots and lianas. We found that H. cooki was not drastically affected by the loss of riparian vegetation, maintaining similar densities of males in both streams, probably because small remnants of native forests were still found near to the stream.

Keywords: shade, survival, population density, body size, copulation, dragonfly

Issue section: Review