The Oregon Zoo has collected more than 8,000 eggs from 32 rare Oregon silverspot butterflies — by far the most it has ever collected during eight years of involvement in a captive-rearing program to help save the delicate creatures from extinction.
Previously, the most eggs collected had been 5,200. After a year of care, the zoo will release the endangered butterfly pupae at the Nature Conservancy’s 280-acre Cascade Head Preserve, north of Lincoln City, where they will emerge as butterflies.
This year, female silverspot butterflies were collected from Mt. Hebo and induced to lay eggs at the Oregon Zoo’s butterfly-breeding facility. The butterfly eggs are collected daily and put into petri dishes where they hatch into tiny larvae.
“Each larva is only about one millimeter long when it hatches,” said Mary Jo Andersen, butterfly conservationist. “They look like tiny specks, but when you observe them under a microscope, you can see that they are perfect miniature caterpillars.”
These tiny caterpillars are then placed in special jars and cooled in refrigerators during the winter, simulating their winter period of inactivity, known as diapause.
“In the spring, we bring them out of diapause and raise the young caterpillars throughout the summer,” said Andersen. “They’re fed the rare plant Viola adunca, and when they pupate we release them back into the wild, where they emerge as beautiful butterflies.”
“This conservation effort is serving as a model for rebuilding an ecosystem,” said Tony Vecchio, Oregon Zoo director. “Through the combined efforts of Seattle’s Woodland Park Zoo, the Nature Conservancy, and the
U.S. Fish and Wildlife Service, we hope to stabilize the butterfly population and bring it back from the brink of extinction.”
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 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.
In 1999, in response to the dramatic decline in the butterfly population, the Oregon Zoo in Portland, Woodland Park Zoo in Seattle, the Nature Conservancy, Washington State Fish and Wildlife, U.S. Fish and Wildlife Service and others took action to save the threatened species and its habitat.
Currently, the Nature Conservancy, working collaboratively with U.S. Forest Service, is restoring the native butterfly habitat through small, controlled burns. Scientists hope that by bringing back the western blue violet — which silverspot caterpillars depend on for food – the butterfly population can return to its historic numbers and ranges.
“Our cooperative conservation efforts are being seen more and more as part of the new zoo ethic,” said Andersen. “It’s becoming quite common for zoos to work outside their traditional captive programs to aid in the protection of species in their natural habitats.”
The zoo is also involved with conservation projects involving Taylor’s checkerspot butterflies and Mardon skipper butterflies.
According to Vecchio, 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 supported 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 North American 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, Oregon silverspot butterflies, western pond turtles and Kincaid’s lupine. Other projects include studies on black rhinos, Asian elephants, polar bears and bats.
(From a press release sent by Bill LaMarche, Oct 2, 2006)
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