The Thorne's hairstreak butterfly has been recognized as unique and imperiled since it was first described as a species in 1983. And with the designation of federal wilderness over its entire range, some threats were eliminated. But wilderness doesn't come with fire insurance, and overly frequent blazes are a tremendous threat to the Thorne's hairstreak. The worst blow yet to the butterfly — and its rare host plant, the Tecate cypress — came in 2003, when the Mine fire tore across 46,000 acres of the San Ysidro (Otay) Mountains. A single new wildfire could terminate the species once and for all.
All five remaining populations of the Thorne's hairstreak are located inside the U.S. Bureau of Land Management's Otay Mountain Wilderness, public land protected from the destructive activities of developers. But Otay Mountain's native plant and animal communities have suffered from dozens of accidental fires — far more than occurred in this area prior to European settlement. About 68 percent of Thorne's hairstreak habitat was lost to the 2003 Mine fire.
To protect the species and call attention to its peril, the San Diego Biodiversity Project petitioned the U.S. Fish and Wildlife Service to list the Thorne's hairstreak as endangered in 1991. But the Service rejected the petition on a technicality, declaring that necessary information was missing (at the same time admitting to already possessing that information). The Service also failed to conduct the status review it promised. Although, in 1984, the Service had declared the Thorne's hairstreak a Category 2 candidate for listing — meaning that listing would be “possibly appropriate” if more information was known — even this status was removed in 1996 when the Candidate 2 list was abolished.
In 2006, two years after the Center submitted another petition to list the butterfly — and one year after we filed a lawsuit to force a response to the petition — the Service announced that it would continue to do nothing for the Thorne's hairstreak. After we sued again, in April 2010 the Service announced that the butterfly warrants consideration for federal protections, but it again denied protections in 2011. Endangered Species Act protection for the Thorne's hairstreak should initiate specific recovery measures such as improved fire suppression, restoration of Tecate cypress habitat, and efforts to increase the number of Thorne's hairstreak populations and individuals.
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2006 government documents supporting 12-month status review
2006 90-day finding denying Endangered Species Act listing
2004 federal listing petition
ENDANGERED SPECIES ACT PROFILE
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Golden State Biodiversity Initiative
The Endangered Species Act
Contact: Ileene Anderson