Oregon Zoo, Conservation Partners Work to Restore Silverspot Butterfly Population

By Bill LaMarche

Portland, OR - A group of Northwest butterfly conservationists got some great news at its end-of-year recap meeting. After comparing notes and crunching a few numbers, the group realized that the Oregon silverspot butterfly, a species it's been working hard to stabilize, may finally have gained a foothold at a key spot on the Oregon coast.

Each December, conservationists from the Oregon Zoo, Seattle's Woodland Park Zoo, Lewis and Clark College, the Nature Conservancy and the U.S. Fish and Wildlife Service meet to discuss strategy and assess the past year's work. For 10 years, these organizations have been rearing silverspot larvae and pupae, then releasing them into the wild in an effort to stabilize and revitalize the dwindling native populations.

It hasn't always been encouraging. At one release site, on U.S. Forest Service land near Yachats on the Oregon coast, fewer than 20 silverspots had been observed in previous years -- some years, only one or two butterflies were detected.

In 2009, though, a field biologist estimated more than 400 butterflies to be in the area.

"This is terrific news and strong evidence that what we're doing is really making a difference in the field," said Oregon Zoo conservation scientist David Shepherdson. "The rearing of plants by our living collections and horticulture staff both to feed larvae and restore habitat has played a critical role in the restoration of this species."

The zoo's horticulture department raised thousands of western blue violet (Viola adunca) starts to plant at the release site, providing a crucial food source and allowing the larvae to pupate.

Zoo butterfly conservationist Mary Jo Andersen was particularly encouraged by the fact that silverspots released at the site this year developed from the caterpillar stage, a good indicator that the population is sustainable and can return in years to come.

Overall, the zoo released more than 2,000 of the rare Northwest butterflies in 2009, including 806 larvae to the site near Yachats, and an additional 600 pupae each to release sites at Cascade Head and Bray Point.

"Through our combined efforts, we hope to stabilize the butterfly population and bring it back from the brink of extinction," Shepherdson said.

The Oregon silverspot butterfly is listed as threatened under the U.S. Endangered Species Act. It was once found in coastal grasslands from northern California to southern Washington, but has since disappeared from all but a handful of sites along the Oregon coast due to habitat loss and the disappearance of its host plant, the western blue violet.

During the preceding decade, monitoring at Cascade Head revealed a dramatic decline in the number of butterflies seen flying. In years prior to 1992, average numbers exceeded 1,000 adults, but in 1998, only 57 of the butterflies were found.

Each year, female silverspot butterflies are collected from Mount Hebo and induced to lay eggs at the Oregon Zoo's butterfly conservation facility. The eggs hatch into tiny larvae (caterpillars), which are kept in refrigerators over the winter, when they are in a dormant stage called diapause (similar to hibernation).

"Each larva is only about one millimeter long when it hatches," Andersen said. "They look like tiny specks, but when you observe them under a microscope, you can see that they are perfect miniature caterpillars."

The Oregon silverspot captive-rearing effort is a project of the NW Zoo & Aquarium Alliance, which promotes collaboration on regional conservation among zoos and aquariums in the Pacific Northwest.

Over the past decade, the zoo has collaborated with the U.S. Fish and Wildlife Service, the Nature Conservancy, the Oregon Department of Fish and Wildlife, the Washington Department of Fish and Wildlife and the Xerces Society to successfully raise and release Northwest butterflies.

In addition to conserving Oregon silverspots, the zoo has enjoyed phenomenal success in its work with the endangered Taylor's checkerspot, raising and releasing thousands of these butterflies over the past six years.

According to Andersen, butterfly populations throughout North America are in decline, with 23 species listed as either endangered or threatened. To address this problem, the Oregon Zoo has been a charter member of the Association of Zoos and Aquariums' Butterfly Conservation Initiative, which involves nearly 50 national zoos and aquariums. The initiative is designed to bring together government and non-government agencies to aid in the recovery of imperiled butterflies.

The zoo is a service of Metro and is dedicated to its mission to inspire the community to create a better future for wildlife. Committed to conservation, the zoo is currently working to save endangered California condors, Washington's pygmy rabbits, Oregon silverspot and Taylor's checkerspot butterflies, western pond turtles, Oregon spotted frogs and Kincaid's lupine. Other projects include studies on black rhinos, Asian elephants, polar bears and bats.

The zoo opens at 9 a.m. daily and is located five minutes from downtown Portland, just off Highway 26. The zoo is also accessible by MAX light rail line. Zoo visitors who travel to the zoo via MAX receive $1.50 off zoo admission. Call TriMet Customer Service, 503-238-RIDE (7433), or visit www.trimet.org for fare and route information.

General admission is $10.50 (ages 12-64), $9 for seniors (65 and up), $7.50 for children (ages 3-11) and free for those 2 and younger; 25 cents of the admission price helps fund regional conservation projects through the zoo's Future for Wildlife program. A parking fee of $2 per car is also required. Additional information is available at www.oregonzoo.org or by calling 503-226-1561.

Caption: An Oregon silverspot butterfly displays its distinctive markings. In 2009, the Oregon Zoo and its conservation partners released 2,000 of these rare Northwest beauties, reared at the zoo's butterfly conservation station, in an effort to stabilize the declining population. Photo by Michael Durham, courtesy of the Oregon Zoo.

Oregon Zoo " 4001 SW Canyon Rd. " Portland, Oregon 97221 " 503-226-1561

To view Oregon Zoo's web page on Zoo and Aquarium Visitor, go to:  http://www.zandavisitor.com/forumtopicdetail-382-Oregon_Zoo