Sequoia Park Zoo Butterfly Conservation Program
Sequoia Park Zoo partners with the U.S. Fish and Wildlife Service to support the recovery of rare coastal butterflies. Most of our work has focused on the Del Norte population of the Oregon silverspot butterfly (Speyeria zerene hippolyta), one of the last five remaining populations of this federally threatened species. The Del Norte population occurs in the dunes and coastal prairies near Lake Earl, CA and its habitat has been badly degraded by coastal development and invasive species.
One way the Zoo helps Oregon silverspots is to remove Scotch broom from potential butterfly habitat. These woody shrubs are extremely invasive because each plant produces thousands of seeds each year, quickly overgrowing the meadows that support the Oregon silverspot’s host plant, early blue violet (Viola adunca). Sequoia Park Zoo partners with the U.S. Fish and Wildlife Service, Tolowa Dune Stewards, California Department of Fish and Wildlife, and Tolowa Dee-ni’ Nation to organize an annual community work day to remove Scotch broom from the Lake Earl Wildlife Area. Since 2014, we have removed over 200 cubic yards of Scotch broom!
In response to a devastating population crash in 2016, Sequoia Park Zoo has cultivated techniques for captive-rearing butterflies, based on methods pioneered by the Oregon and Woodland Park Zoos. We collect eggs from adult butterflies, hatch them in a lab, and rear the caterpillars to pupae, which are released back into the wild to supplement declining populations. We are currently permitted to captive-rear Oregon silverspot butterflies to assist USFWS in the recovery of the Del Norte population. We are also pursuing a permit to captive-rear Behren’s silverspot, a closely related endangered butterfly that occurs as a single population in Mendocino county.
Oregon silverspot caterpillars only feed on a single species of violet, the early blue violet, and they need a lot of it to grow! Although managers have planted violets to restore Oregon Silverspot habitat, they have not seen the expected increases in butterfly numbers. One theory for this lack of population growth is that invasive dandelions in the habitat might distract caterpillars from finding violets. It has been casually observed that when caterpillars encounter dandelions, they interrupt their foraging to circle the plant. The Zoo is conducting behavioral experiments with caterpillars to rigorously test this theory, so we can inform managers whether it is important to commit time and money to eradicating these common weeds from butterfly habitat.
Ways You Can Help
- The annual “Scotch Broom Bash” typically occurs in March or April, and is a family friendly community event. Spend the day with us at Lake Earl, cutting down Scotch broom to create new butterfly habitat, and meeting new people! Tools, snacks, and transportation from Arcata to Lake Earl are provided.
- Become a violet volunteer! In the spring, our hungry caterpillars gobble down over 7000 violet leaves and it can take 12-15 hours per week to harvest enough leaves to keep them fed. Volunteers work behind the scenes at the zoo to pick the choicest leaves from our potted violets. The schedule is flexible and caterpillar season typically runs from April to July.
- Donate! The Butterfly Conservation Program is funded entirely through grants and donations so all donations help keep us flying.