Taylor’s checkerspot butterfly reintroduction in the Puget lowland prairies of Washington State, USA

Summary

Taylor's checkerspot butterfly (Euphydryas editha taylori), an Endangered grassland specialist of the Puget lowland prairies, had been reduced from 80 historical sites to just 11 by 2008, with its largest surviving population confined to a restricted military artillery range in Washington State. Since 2004, the Washington Department of Fish and Wildlife has worked with the Oregon Zoo and Mission Creek Corrections Center to rear postdiapause larvae for reintroduction, collecting wild females for oviposition under federal permit alongside captive-mating adults from prior years' wild-collected larvae, achieving over 90% survival from hatch to adult. After mapping historic prairie restoration sites against habitat-suitability thresholds from the source population, teams released mature larvae in small groups (741-3,621 per site annually) onto host plants at densities of at least three per square metre, aiming for over 1,500 larvae per site annually across five years, a target met in 7 of 12 recent releases. Post-release monitoring found weighted average postdiapause survival of 0.50 from 2014-2016, comparable to wild rates for related subspecies; one reintroduced population reached a peak single-day abundance of 3,391 adults in 2016, meeting the establishment threshold, and a second showed strong growth expected to qualify by 2021, while three single-release sites failed to persist. Restricted military-land access, unpredictable weather affecting prescribed burns and captive oviposition, and the difficulty of monitoring a cryptic, multi-stage insect were the main obstacles. The project rates itself successful, crediting sustained multi-agency funding, redundant rearing facilities, and large-scale cooperative habitat restoration despite the inherent fragility of any single release.