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Island Marble Butterfly: Slipping Towards Extinction

By sarina jepsen on 5. April 2016
sarina jepsen

In the last 15 years, the island marble has been slipping away; there is now only one surviving population. The U.S. Fish and Wildlife Service denied it protection. 

On Tuesday, April 5, 2016, the United States Fish and Wildlife Service (Service) announced that the island marble butterfly (Euchloe ausonides insulanus) is in danger of extinction but that protection under the Endangered Species Act is “precluded by higher priority listing actions.” The Service declined to grant this butterfly protection through an emergency listing process, as requested in a 2012 petition filed by the Xerces Society, despite recognizing that there is only one remaining population of the island marble butterfly. Rather, this species was placed on a list of candidate species, which do not receive any of the same protections as ESA listed species.

We are very disappointed that the protection of the island marble has not been prioritized. This is perhaps the most endangered species I’ve ever worked with. After a decade of falling numbers, this butterfly survives at only one site—and yet our public agency that is responsible for safeguarding wildlife has failed to recognize the urgency of this species’ situation.

Scott Hoffman Black, executive director of the Xerces Society, said, “We are glad that the USFWS has found that the island marble is warranted for listing. But we find it unfortunate that this highly endangered species will not receive the protection it needs under the ESA.”


island marble butterfly
In the last 15 years, the island marble has been slipping away; there is now only one surviving population. The U.S. Fish and Wildlife Service denied it protection. Photo: Keith Van Cleve


The Xerces Society has been working to save this butterfly for 15 years. In December 2002, the Society was joined by the Center for Biological Diversity, Friends of the San Juans, and the Northwest Ecosystem Alliance to submit a petition requesting protection. That petition was denied four years later.

The threats facing the island marble remained and the population of the butterfly continued to decline, as it was lost from site after site in the San Juan Islands of Washington state. Consequently, Xerces submitted a second ESA petition in August 2012. Tuesday’s announcement is in response to that.

The principle threats to the island marble and its habitat are herbivory by black-tailed deer and European rabbits, plant succession and competition with invasive species, and a projected increased frequency in storm surges, which could all reduce or destroy habitat.

In the Federal Register announcement, the Service recognized that these threats affect the butterfly throughout its range, are likely to persist, are of a high magnitude, and are “sufficient to put the subspecies is in danger of extinction or likely to become so in the foreseeable future.” Despite this, the Service declined to provide the island marble butterfly with the protection that it needs.

Will the island marble slip away under the watch of the agency responsible for its protection?

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