Willamette Valley butterfly once considered extinct is back in strong numbers

A butterfly native to the Willamette Valley and that was once thought to be extinct has returned in strong numbers. 

The Fender’s blue butterfly will move from the endangered to threatened species list under the federal Endangered Species Act on Feb. 13, federal officials said.

The U.S. Fish and Wildlife Service said in a statement that the classification change followed an expansion of its habitat during the last two decades due to conservation efforts on public and private lands. 

Conservationists say the butterfly is an important pollinator in the Willamette Valley and that its return marks an improvement in prairie biodiversity and health. The butterfly, found only in the Willamette Valley, was thought to be extinct in 1937, according to the federal fish and wildlife service, but a small number were rediscovered in the late 1980s. At the time, the butterfly was barely hanging on due to threats from development and fire suppression efforts that destroyed prairies and a wildflower it depends on. The butterfly lays its eggs in Kincaid’s lupine, and the wildflower feeds the larvae once they’re hatched. 

By 1993, it was estimated that about 3,000 of the Fender’s blue butterflies existed, but over the years, the numbers fluctuated from more than 6,000 to about 1,750 according to the Institute for Applied Ecology, which conducts annual population surveys for the fish and wildlife service. In 2000, when its numbers hovered around 4,000, the butterfly was declared endangered. Under the Endangered Species Act, plants and animals receive federal protection.

Over the past two decades, efforts from federal and state agencies, and agreements with private landowners to improve habitats for the butterfly, have helped it reestablish itself in the area. 

As of 2020, the population was estimated to be about 19,000, according to the institute. 

The Fender blue butterfly’s habitat has doubled since 2000, and the population was estimated to be about 19,000 as of 2020, according to the Institute for Applied Ecology. They can be found from mid-April through June in Benton, Lane, Linn, Polk, Washington and Yamhill counties, as well as the Baskett Slough National Wildlife Refuge near Salem and the Nature Conservancy’s Willow Creek Preserve near Eugene.