Rare Butterfly Wins Endangered Species Protections

Ninety years after it was thought to have gone extinct, the island marble butterfly won protections from the Trump administration that include setting aside part of its only known habitat.

The U.S. Fish and Wildlife Service finalized federal wildlife protections for the rare island marble butterfly, which is only known to be viable on San Juan Island in Washington state. (Karen Reagan / U.S. Fish and Wildlife Service )

(CN) — The U.S. Fish and Wildlife Service finalized federal wildlife protections for the endangered island marble butterfly on Monday and designated a part of San Juan Island in Washington state as protected habitat for the nonmigratory species.

The rare butterfly, which has white and green marbled wings, was only known to exist on Vancouver Island and the Canadian Gulf Islands off the coast of British Columbia. 

Surveyors believed the species — scientific name euchloe ausonides insulanus — had gone extinct after it was last observed on Gabriola Island, Canada, in 1908.

But 90 years later, researchers spotted small populations of the butterfly species in the San Juan Island National Historical Park.

Today, the only known viable population of the island marble is found on San Juan Island’s coastal shoreline, lagoons, sand dunes and adjacent prairieland, which have declined 97% from their historical size according to a 2002 petition by conservation groups the Center for Biological Diversity, Friends of the San Juans and others.

The main threats to the species’ habitat are road construction through the park, pesticide use in and around the park, and private land development around the butterfly’s historic range, according to the petition.

Meanwhile, black-tailed deer, brown garden snails, rabbits and plants that displace larval host plants have all decimated the butterfly’s habitat over time.

The conservation groups sued the U.S. Fish and Wildlife Service multiple times to force the federal agency to respond in a timely manner to the petition and determine whether the island marble should be protected under the Endangered Species Act of 1973. 

The federal agency, along with the Washington State Department of Fish and Wildlife, concluded in 2018 the invertebrate species was a candidate for protections under the act.

In a 127-page unpublished rule posted Monday, the federal agency said after reviewing multiple studies and public comments it determined the threats faced by the butterfly warrant listing under the act.

The rule says that existing state and federal regulations on zoning and development and local conservation rules generally lead to conditions that are beneficial to the species.

“However, this impressive suite of regulatory mechanisms has not prevented the extirpation of other populations, and the species remains in precarious shape with only one remaining known location,” the rule states. “Therefore, we conclude that the existing federal, state, and local regulatory mechanisms provide some benefits to the island marble butterfly and its habitat, but do not sufficiently ameliorate the threats to the species such that it does not meet the definition of an endangered species.”

The rule finalizes endangered species status for the island marble butterfly, which could bring in federal funding to local conservation efforts aiming to expand the species’ habitat and preserve its range.

The agency said threats to the species include continued insecticide application within the habitat and vehicles running over the butterflies, which are attracted to white stripes on the road. 

“Because the island marble butterfly persists in low numbers, loss of a portion of the remaining population could have disproportionately negative effects,” the rule states. “While there have been no specific reports of island marble butterfly road kills, the presence of the highway within occupied habitat exposes the species to potential vehicle collisions.”

A spokesperson for the conservation groups did not immediately respond to a request for comment by press time. 

The federal agency’s rule also designates 812 acres of critical habitat for the island marble on the south end of San Juan Island.

Only two acres of the designated habitat are privately owned, according to the rule.

The move will complement existing preservation efforts by the National Park Service — owner and steward of the island marble habitat — which has been collecting and rearing eggs and establishing habitat patches fenced to keep deer out.

Fish and Wildlife’s final rule will be published Tuesday in the Federal Register.

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