The butterfly conservation team at the Oregon Zoo works year round, from egg collection to release, to help two native species recover some of their historic range.
The Oregon Zoo began its recovery efforts with the Oregon silverspot butterfly in 1999, and added the Taylor’s checkerspot in 2003. Zoo staff work to save these beautiful pollinators from extinction with partners from the U.S. Fish and Wildlife Service, Washington Department of Fish and Wildlife, Xerces Society, the Nature Conservancy, Woodland Park Zoo, Washington Department of Corrections, Department of Defense and several local universities.
The Oregon silverspot butterfly (Speryeria zerene hippolyta) inhabits coastal grasslands near the Pacific Ocean from northern California to southern Washington. The caterpillars' only host plant is the early blue violet (Viola adunca).
Silverspot butterfly populations have declined due to:
- habitat loss resulting from development of coastal headlands
- habitat degradation due to invasion of non-native plant species resulting in reduced food availability
- fire suppression and changes in grazing, resulting in additional habitat degradation and reduced food availability, allowing grasses and woody plants to grow and shade out the caterpillar's only food plant, the early blue violet.
Once common on the Oregon Coast, the butterfly was reduced to four Oregon populations by the 1990s. The species was listed as threatened by the U.S. Fish and Wildlife Service in 1980; one of two Oregon butterflies listed as threatened or endangered under the U.S. Endangered Species Act.
Oregon silverspot recovery
A population crash in 1998 prompted USFWS to begin a population supplementation program in partnership with the Oregon Zoo and the Woodland Park Zoo in Seattle, Wash. Supplementing the wild populations with zoo-reared butterflies prevents extinction of existing populations and allows for the possibility of reintroducing butterflies to their former range.
What the recovery project looks like:
- Late summer: Conservation biologists in the field capture adult female butterflies and bring them to the zoo butterfly conservation laboratory where they lay eggs. The eggs are hatched in special jars to maintain humidity.
- Winter: The jars containing tiny caterpillars are placed in fridges to simulate winter on the Oregon Coast. During this phase, called “diapauses,” the caterpillars are mostly inactive.
- Spring: The caterpillars are removed from their jars and fed with violet leaves grown on zoo grounds. They grow rapidly through six instars (phases of molting) over a period of six to eight weeks. At the end of this time they pupate in preparation for metamorphosing into butterflies.
- Summer: The pupae are taken from the zoo and placed in protective release cages on the coast. Biologists watch them every day and when the butterflies "eclose" or emerge from their pupae cases, they are released to join free flying wild butterflies.
- Fall: Plants grown at the zoo and other sites are planted in the butterfly habitat to provide food for caterpillars and butterflies in the future, restoring the habitat.
Successes and ongoing recovery work
About 2,000 butterflies are released each year at the Oregon Coast. Studies suggest many existing populations would have gone extinct without help from zoo-rearing programs. There are now thriving populations of butterflies at sites that hosted almost no butterflies just a few years ago. In coming years, zoo staff hopes to release butterflies at some of the sites from which they recently went extinct. In 2012, the Oregon Zoo and Woodland Park Zoo were awarded the AZA's North American Conservation Award for the "significant achievement" of their cooperative Oregon silverspot butterfly captive rearing program.