EUGENE, Ore. -- The population of endangered Fender's blue butterflies has doubled at Fern Ridge Reservoir since last year, according to a U.S. Army Corps of Engineers survey.

The Corps' 2012 estimate of 3,769 Fender's blue butterflies at 11 sites near the reservoir west of Eugene, Ore., is the species' largest known population and continues a trend of positive population growth since it was first detected on Corps lands in 1998. 2011 surveys estimated a population of 1,687 butterflies.

This species of butterfly, found only in Oregon's Willamette Valley, was believed to be extinct from 1937 until it was rediscovered in 1989. The species was listed as endangered in 2000.

The known population of Fender's blue butterflies has increased dramatically since their rediscovery. Corps biologists credit a combination of factors for the species' recovery, including restoration of prairie habitat by planting the butterfly's larval host, the federally protected Kincaid's lupine; control of invasive species; discovery of new populations; and improved monitoring methods.

Recovery of the Fender's blue butterfly and other prairie species of Western Oregon and Southwest Washington is a collaborative effort between the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, U.S. Bureau of Land Management, U.S. Geological Survey, Oregon and Washington state agencies, and a variety of non-governmental organizations.

The U.S. Army Corps of Engineers is restoring degraded ecosystems and aquatic health.
We strive to protect, sustain, and improve the natural and man-made environment of our nation, and are committed to compliance with applicable environmental and energy statutes, regulations, and Executive Orders. Sustainability is not only part of the Corps' decision processes, but is also part of its culture.