Reintroduction of the rare damselfly Ischnura gemina (Odonata: Coenagrionidae) into an urban California park

Habitat degradation led to local extinction of the San Francisco forktail damselfly (Ischnura gemina) in Glen Canyon Park, San Francisco, California. In this study, we reintroduced I. gemina into Glen Canyon after the damselfly’s habitat was restored. Upon release, we carried out a mark-release-recapture study to monitor the damselfly’s population dynamics. Our data were compared to two “baseline” studies on I. gemina, conducted in the park prior to the damselfly’s demise. Our recapture rates were significantly lower than the prior studies due to a large initial decline in marked individuals upon release. Despite a lower recapture rate, the reintroduction was initially successful since the damselflies reproduced throughout the summer and the following year. However, the population failed to persist during the second year when the habitat became degraded with excess vegetation. Future success is contingent on the continual management and upkeep of the habitat.