Zoo butterfly lab is on track for an egg-ceptional year

October 7, 2016 - 1:41pm

Program aims to boost imperiled populations of the once-common Oregon silverspot

The Oregon Zoo’s butterfly conservation lab was aflutter with activity this week as egg-laying season for the Oregon silverspot drew to a close. Over the past month, nearly 1,900 silverspot eggs have been laid at the zoo lab as part of a focused conservation partnership aimed at saving this imperiled Northwest pollinator.

"If it weren’t for this program, three of the five remaining silverspot populations would likely be extinct."

—Karen Lewis, conservation research associate

Each summer, female silverspots are collected by field biologists with the U.S. Fish and Wildlife Service and U.S. Forest Service, and are brought to the zoo to lay eggs. The eggs hatch into tiny larvae (caterpillars), which are kept safe at the zoo over the winter.

In the spring, they wake up to a leafy meal, grow quickly and pupate. Then, when the weather grows warmer, the zoo and its conservation partners transport the pupae to field sites along the Oregon Coast to begin the cycle anew.

This past summer, nearly 450 Oregon Zoo-reared silverspots were released among the grassy headlands and salt-spray meadows that make up some of the last remaining habitat for the butterfly.

Listed as threatened under the federal Endangered Species Act, the Oregon silverspot was once common in coastal grasslands from northern California up into British Columbia, but has since vanished from all but five sites due to habitat loss and the disappearance of its host plant, the early blue violet.

“The goal of the recovery program is to help each population grow large enough to be self-sustaining,” said zoo conservation research associate Karen Lewis. “If it weren’t for this program, three of the five remaining silverspot populations would likely be extinct.”