Oregon Silverspot Butterfly Recovery Programme
To breed and reintroduce Oregon silverspot butterflies to supplement stocks in the USA
The Oregon Silverspot Butterfly, Speyeria zerene hippolyta, requires one of three types of grasslands with nearby meadows. These are: coastal salt spray meadows, stabilized dunes, and/or montane meadows which are surrounded by forests. The grasslands that the Silverspot inhabits provide larval host plants, adult nectar sources and wind protection. The wind protection is provided by the forest fringes around the meadow in which the butterfly may retreat on especially windy days.
Although its native range is from Washington state down to northern California, its populations are small and isolated within its coastal grassland habitats. One factor that severely restricts its population is that its preferred food plant is the early blue, or dog, violet (Viola adunca). This beautiful little violet, once prevalent on Washington’s Long Beach peninsula and other places, is now disappearing as its habitat is gobbled up by development. Therefore, in 1980, the Oregon silverspot butterfly was declared a federally threatened species.
In 1999, the U.S. Fish and Wildlife Service established the Oregon Silverspot Butterfly Recovery Program, a captive rearing and release program, in partnership with the Oregon Zoo and Lewis and Clark College. Cascade Head Preserve in Oregon, a site established by The Nature Conservancy that contains abundant remaining patches of violets, serves as the release site. In 2001 the Woodland Park Zoo joined in to directly aid the effort by headstarting silverspots here at the zoo.
The main goals of the entire recovery program are to:
- Protect the existing habitat.
- Manage the habitat.
- Monitor the populations.
- Protect additional habitat.
- Reduce take.
- Increase existing populations through ex situ rearing and augmentation.
- Reintroduction in suitable habitats.
The goals of the Woodland Park Zoo population augmentation project are to:
- Increase the number of captive raised butterflies for release.
- Provide an additional facility for the larval rearing so not “all the eggs are in one basket”.
- Experiment with rearing techniques with a view to optimizing the program.
Headstarting the Silverspot
The headstarting has proven extremely successful; a wild butterfly census taken in September 2000 showed a population of 80 butterflies, as opposed to fifty the previous year. By increasing population numbers to this level, efficient monitoring can take place, and the species will not become extinct while attempts to understand and reverse declining trends are undertaken.
Growing the Population
Population augmentation is a complicated process, and Woodland Park Zoo participates directly in this project by rearing the butterflies in Zoo facilities. In September, adult female butterflies are captured from the population at Cascade Head, OR, and transferred to the Zoo. Eggs are laid and then subsequently hatched. The newly emerged caterpillars are hydrated and fed, and placed in a laboratory setting that induces diapause (a period of no growth or development) as from September. In May the caterpillars are raised upon violet leaves, where they grow larger and larger until they pupate, and the pupae are returned to the site of the wild population at Cascade Head, where they will emerge as adults and renew their reproductive cycle. Woodland Park Zoo is currently experimenting with a view of optimizing rearing techniques.
Preserving a Vital Habitat
Ex situ population augmentation is but one part of this project. Using mowing and controlled burning techniques, project ecologists attempt to increase the quality of habitat for the butterfly. Most importantly, project scientists are closely monitoring the butterfly in order to better understand its problems. In the future, scientist may attempt to reintroduce the Oregon silver spot butterfly to Washington's Long Beach Peninsula, where a historic population once existed.
The Woodland Park Zoo’s Wild Wise program recruits and trains Seattle-area schools to take between 5 and 25 violet plants to raise throughout the spring. The plants are then brought back to the zoo for the butterfly instar larva to eat. The students monitor leaf growth and send their data to the zoo regularly, which are posted on a special zoo website so schools can track how the plants were growing. In addition, the Zoo Corps teen volunteer group continue to assist in silverspot rearing and one teen interns with Sullivan. This encourages students to study all the various facets of science that go into the important work of conserving a species and its habitat.
WAZA Conservation Project 05034 is implemented by the Woodland Park Zoo and Oregon Zoo, in partnership with the Washington State Department of Fish and Wildlife, USFW, Willapa National Wildlife Reserve, North Coast Land Conservancy, The Nature Conservancy, Hebo Ranger District-Siuslaw National Forest, California Fish & Game, Oregon Military Department, and Oregon Dept. of Transportation Environmental Service.
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