Re-introduction of the San Francisco forktail damselfly into an urban park, California, USA

Summary

The San Francisco forktail damselfly (Ischnura gemina), Vulnerable and endemic to the Bay Area, went locally extinct from Glen Canyon Park in the late 1980s from habitat degradation, prompting San Francisco State University researchers to restore its former breeding channel and attempt reintroduction in 1996-1997 after clearing overgrown vegetation and having the California Conservation Corps build new pond habitats nearby. Roughly 40 mating pairs were collected from the nearest known population, about 12 km south, transported in a cooler to minimize stress, individually marked, and released the next morning at the historic breeding channel; mating pairs were chosen to guarantee both sexes, confirm reproductive maturity, and reduce handling damage compared to juveniles. Post-release monitoring found survival and movement patterns comparable to pre-extinction studies after an initial larger-than-expected drop in recapture rates, with damselflies mating and ovipositing normally and dispersing to the new ponds; at least two generations of new adults emerged in 1996, and damselflies again emerged in spring 1997, but the population failed to persist into that fall, and none have been found in subsequent yearly visits. Major difficulties included the ongoing need for active habitat maintenance given the loss of natural ecological processes, and the absence of any nearby population to enable natural recolonization or gene flow. The project rates itself a Failure, though it demonstrated adult-based damselfly reintroductions can succeed short-term, and the City of San Francisco plans a repeat attempt if the species remains absent after five years.