Category: Status Reports
Published: February 2019
Author(s): David W. Hays and Derek W. Stinson
The Oregon silverspot (Speyeria zerene hippolyta), a striking butterfly of the Pacific Northwest coast, was listed as endangered by Washington State in 1993, and threatened under the federal Endangered Species Act in 1980. Oregon silverspots historically occurred in coastal settings from Grays Harbor County in Washington, south through Oregon and into northern California. In Washington, it inhabited sites along the coast from Westport to the Columbia River. Today, all but 5 localities (one in California and 4 in Oregon) have been extirpated. A population persisted in Washington on the Long Beach Peninsula through at least 1985, when intensive searches revealed a few butterflies remaining. The most recent surveys in Washington, in 1991 and 1996 found no Oregon silverspots, and in 1996 no suitable habitat. The butterfly is thought to be extirpated from Washington.
The Oregon silverspot occurs in three types of early successional coastal grasslands and adjacent forest fringes: coastal salt spray meadows, stabilized dunes, and montane meadows. Within these grasslands, silverspots have three primary habitat requirements: 1) larval hostplants; 2) adult nectar sources; and 3) features that provide protection from wind. The butterflies emerge in late-summer and the females lay eggs on or near early blue violet (Viola adunca), the sole host plant. Eggs hatch in the fall and larvae seek a secure overwintering site and remain dormant until the following spring, when they commence feeding on the violets. The larvae pass through six growth stages before pupating and emerging as butterflies. Adults feed in meadows on floral nectar from herbaceous plants including aster (Aster spp.), goldenrod (Solidago spp.), pearly everlasting (Anaphalis margaritacea), false dandelion (Hypochaeris radicata), and thistle (Cirsium spp.), and seek refuge in glades and forest edges for protection from strong coastal winds. Habitat loss and degradation are the primary causes of the decline of the Oregon silverspot in Washington and throughout its range. Seaside meadow sites have been developed for residential and business establishments, public parkland, parking areas or lawns. Trees, shrubs, and exotic grasses have invaded the butterfly's meadow habitat, resulting in the loss of food plants. Washington Department of Fish and Wildlife has been conducting management and recovery efforts aimed at acquiring and restoring suitable habitat since 1990. The U.S. Fish and Wildlife Service has also been working to develop techniques to restore habitat at Willapa National Wildlife Refuge and at sites in Oregon.
The Oregon silverspot is likely extirpated in Washington, and will require reintroduction from captive reared or wild populations in Oregon. There is no classification for extirpated species in Washington. We recommend that the Oregon silverspot remain classified as endangered in the State of Washington.