Migratory butterflies enchant Richmond Field Station grove

A Monarch butterfly rests on the ground at the campus's Richmond Field Station, a wintering area for the species. Gerald Stone photo.

08 NOVEMBER 00 | An annual ritual is now unfolding at Richmond Field Station, where the Monarch butterflies have returned to wait out winter in the eucalyptus grove.

A celebrity-status butterfly, the Monarch is renowned for its dramatic orange and black markings and its remarkable seasonal migrations to the same wintering spots year after year. Among a handful of local sites with most-favored roosting status is the 150-acre Berkeley campus outpost on the east shore of San Francisco Bay.

Even for field station staff spoiled by the siteÕs profusion of wildlife Ñ from possums, raccoons, skunks and ground squirrels to hawks and hummingbirds Ñ the MonarchsÕ yearly visit is a treat.

Linda Ohotsky, an administrative assistant for the Institute of Transportation Studies, has spent many lunch hours outside her field-station building at the corner of Lark and Gull streets.

"You sit very quietly and watch the trees, and all of a sudden you start seeing them," Ohotsky says. "They flap and then they glide and they chase each other. They land for awhile, swoop around, turn curly cues, come and make almost like figure 8Õs. ItÕs as much a miracle as an elephant."

This year the first Monarchs were sighted in the eucalyptus grove late in October, bringing much excitement with their arrival.

"We send out an e-mail when the butterflies come in," says Richmond Field Station Superintendent Scott Shackleton, who has followed the MonarchsÕ annual return to the site since 1982. "ItÕs a changing-of-season point for us."

The butterflies usually stay into January, with the largest number in residence between Thanksgiving and Christmas, says Shackleton.

"On a good year the whole grove is full of them; itÕs just thick," he says. "They usually pile up in the areas where thereÕs lot of exposure to the sun."

One of the largest butterflies in North America, the Monarch, or Danaus plexippus, is also known as "milkweed butterfly," because of its dependence on milkweed.

In the spring and summer months, Monarchs deposit eggs, hatch and dine exclusively on milkweed. The adult butterfly that emerges finally from the chrysalis is resistant to predators thanks to toxic milkweed alkaloids.

Monarchs have tropical ancestors and have "gotten around winter" in North America by retreating to warmer climes during the coldest months, says grad student Dan Rubinoff, a moth and butterfly specialist in the College of Natural ResourcesÕ Division of Insect Biology.

West of the Rockies, they winter on the central and southern California coastline, living on food "theyÕve eaten months and months before," he says. "They need very specific temperatures. If they get too warm, theyÕll use up their fat reserves too quickly and starve."

Coastal forests provide the precise climate conditions, and cover, that the wintering Monarchs need. Pine and redwood trees are their preferred roosts. As those stands are reduced by human activity, the Monarchs settle for eucalyptus, an invasive, non-native evergreen.

"Here and especially in Mexico (where East-coast Monarchs winter), the sites that they roost in are potentially endangered," says Rubinoff.

Scientists are still unable to explain, he says, the MonarchsÕ amazing navigational savvy, especially considering that individuals returning to sites like the Richmond Field Station are two to three generations removed from those who wintered there a year before.

"ItÕs a great mystery how the heck the Monarchs find their way back to their great grandparentsÕ roosting sites," Rubinoff says.

How to reach Richmond Field Station

Richmond Field Station is open to the public from 6 a.m. to 6 p.m., Monday through Friday (closed on weekends and after hours). When viewing the butterflies, visitors are cautioned to stay off the testing track for the computer-operated PATH cars.

By car: Fom Berkeley, take I-80 north to I-580 going toward the Richmond/San Rafael Bridge. Take the Bayview exit. Turn left on the overpass. After the four-way stop, proceed straight, paralleling the freeway for about a quarter mile. Jog to the left at S. 47th street, to the Richmond Field Station entrance kiosk. Parking is available on the grounds.

By campus shuttle: The shuttle to Richmond Field Station leaves Hearst Mining Circle weekdays at 10 minutes after each hour (9:10 a.m. through 3:10 p.m.). It also stops at Center and Shattuck in downtown Berkeley (on Center Street, next to Wells Fargo Bank) at 16 minutes past the hour, starting at 9:16 a.m. The ride costs $.50 and takes about 25 minutes.