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Washington butterfly up for ESA protection

The U.S. Fish and Wildlife reports that subdividing farmland helped shrink butterfly’s range.
Don Jenkins

Capital Press

Published on April 12, 2018 8:28AM

The island marble butterfly, found only on San Juan Island in Washington, is a candidate for the endangered species list. A U.S. Fish and Wildlife report says loss of farmland has shrunk the butterfly’s range.

U.S. Fish and Wildlife Service

The island marble butterfly, found only on San Juan Island in Washington, is a candidate for the endangered species list. A U.S. Fish and Wildlife report says loss of farmland has shrunk the butterfly’s range.


A species of butterfly found on the end of one Washington state island doesn’t fare well around agriculture, but apparently fares even worse when farmland yields to development, according to a report by the U.S. Fish and Wildlife Service.

The agency proposed Tuesday to list the island marble butterfly as an endangered species. Fish and Wildlife last year counted fewer than 200 on the southern end of San Juan Island, mostly on American Camp, a 19th century Army post that’s now part of the San Juan National Historic Park.

To conserve the species, Fish and Wildlife also proposes to designate 812 acres as critical habitat. The butterfly is not known to occupy other areas, but endangered species are protected wherever they appear.

The National Park Service is the largest landowner, with 718 acres. Two acres are privately owned, while other federal, state or local agencies own the rest. The privately owned land is primarily steep coastal bluffs, a Fish and Wildlife spokeswoman said.

More than a decade ago, according to Fish and Wildlife, the butterfly was found in pockets away from the camp on small farms and in rural neighborhoods. Livestock and tilling take out the mustard plants that host the butterflies, yet the agency said it believed the land’s use was compatible with the species.

“Since that time, the amount of farmland in San Juan County has decreased, with the greatest loss of farmland in San Juan County attributed to the subdivision of larger farms into smaller parcels, which have been developed,” according to Fish and Wildlife.

“We conclude that development has substantively contributed to the extirpation of the island marble butterfly outside of American Camp and remains one of several factors impeding successful recolonization of previously occupied habitats.”

The species was once known on Vancouver Island, British Columbia, across the Haro Strait from San Juan Island. The butterfly had not been seen for 90 years until a Washington Department of Natural Resources biologist spotted one in 1998.

The Xerces Society for Invertebrate Conservation and other environmental groups first petitioned Fish and Wildlife to list the species in 2002. Xerces renewed the petition in 2012.

“There has been tremendous effort to assist the island marble butterfly over the years,” Fish and Wildlife’s state supervisor, Erick Rickerson, said in a written statement. “But given the small population size, the threats to this species are significant. We will continue to work collaboratively with organizations and individuals on San Juan Island in our shared concern for the continued survival of this species.”

Top threats identified by Fish and Wildlife include predation by spiders and wasps. Deer, rabbits and snails browse on plants that host butterflies, and storms have swamped habitat.

Potential, though undocumented, threats include butterfly collectors and vehicle collisions.

Male island marble butterflies are attracted to white objects that resemble females. The butterflies could be attracted to the white fog lines of the highway through American Camp and increase their risk of being hit, according to the Fish and Wildlife report.

Fish and Wildlife will take public comments on the proposed listing through June 11.

Comments may be submitted to www.regulations.gov or mailed to: Eric V. Rickserson, state supervisor, Washington Fish and Wildlife Office, 510 Desmond Drive SE, Lacey, Wash., 98506.



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