The Oregon Zoo’s Smallest Inhabitant

Butterfly Conservation at the Oregon Zoo

Mary Jo Andersen is washing butterfly feet. "Their taste buds are on their feet, so when they step on something, they know whether they can eat it,” she explains. This is one of her daily duties as butterfly conservationist at the Oregon Zoo, where Andersen manages the zoo’s butterfly conservation project. The sugar solution they eat, can crack their feet as it dries, so and her team wash the butterflies’ feet after every feeding. They encourage the insects to walk on water-soaked swabs, the same way they introduce food.

The program has been rearing butterflies, including the Oregon silverspot, Taylor’s checkerspot and Mardon skipper, since 1998. The lab is located in a divided warehouse-like space above the zoo’s polar bear exhibit. Inside the “sun tent,” which is lit with sun lamps, warmed with heating pads and kept humid with several humidifiers, checkerspots enjoy a variety of cut wildflowers and cotton swabs soaked with sugar syrup. “This is their retirement community,” says Andersen. “They’ve hatched, pupated and bred, and this is the final stage in their lives."

About the Crisis

The program began at a time when there were just 57 Oregon silverspot butterflies recorded in their Oregon coast habitat. Once found in coastal headlands from northern California to southern Washington, this butterfly has disappeared from all but a handful of sites. In addition to habitat loss, one possible factor in its decline has been fire suppression, which allows grass to overshadow its larval host plant, the western blue violet (Viola adunca).

How the Program Works

During the flight seasons, female butterflies are brought from the coast and induced to lay eggs in laboratories at the zoo. Every day, the butterflies are fed nectar, a solution of sugar water and egg white, from a cotton swab.

The butterfly team checks for eggs daily, peering though leaves of a potted host plant. Eggs turn from yellow to orange to brown to black as they mature. “That’s the head of the caterpillar that’s making it black,” Andersen says. The eggs are put into petri dishes, and after approximately 10 days, many hatch out into tiny larvae. Each larva is about a millimeter long. At this stage, the larvae do not eat, but they are given water by placing them on moist filter paper. For winter diapause (hibernation), the larvae are placed in specially modified jars and put into refrigerators. Keepers vigilantly check them every two weeks and take corrective action if problems arise.

Zoo gardeners raise thousands of western blue violet (Viola adunca) plants for the larvae to feed on after their hibernation. Following winter dormancy, the butterfly larvae are fed these Viola adunca leaves until they pupate. The butterfly team’s daily tasks include recording the amount of food eaten, amount of frass (butterfly feces), growth and other data. After their final molt, or instar, the caterpillars pupate. They are then returned to coastal habitats at Bray Point or Rock Creek, ready to emerge as adult butterflies. This conservation technique, called population supplementation, is intended to prevent inbreeding depression often seen in small populations.

This year, student butterfly interns continue to help staff rear threatened and endangered butterflies, including the Mardon skipper, the Taylor’s checkerspot and the Oregon silverspot. It requires hundreds of hours and dozens of interns and staff to help feed and clean the thousands of butterfly larvae.

A Record Year

In August 2007, the zoo released a record number of Oregon silverspot butterflies. In an effort to save the threatened Oregon silverspot butterfly from extinction, the Oregon Zoo and its conservation partners released more than 500 rare butterfly pupae at three sites on the Oregon coast. “This conservation effort is serving as a model for rebuilding an ecosystem,” says David Shepherdson, deputy conservation manager.

Back in the Lab

One wall of the butterfly lab is lined with refrigerators labeled Caution: Endangered Species. Large windows supply light. A master calendar charts hatchings, caterpillars in diapause, instars (developmental stages between molts) and pupae to be released. Colorful signage shows the life cycle of each butterfly, aimed at educating school groups who tour the lab.

Hunched over a microscope, Andersen examines one of the latest caterpillar hatchlings. If all goes well, this creature will be taken care of through winter hibernation, and released as a pupa next spring. Today, however, the caterpillar is just a millimeter long. It’s hard to believe that just downstairs, there are half-ton polar bears frolicking in their pool. For more information, visit the Xerces Society.