SACRAMENTO, Calif.— A federal judge ruled today that the U.S. Fish and Wildlife Service violated the Endangered Species Act when it refused to designate critical habitat in California for the endangered Sierra Nevada red fox. The court found that the agency committed three separate legal errors in deciding that critical habitat for the fox was “not prudent.”

“This is a huge victory for one of California’s rarest and most beautiful animals,” said Brian Segee, a senior attorney and legal director of the Center for Biological Diversity’s endangered species program. “Sierra Nevada red foxes desperately need safe places to survive and recover, and federal officials can’t simply sidestep their duty to consider protecting these places. I’m thrilled the court rejected this unlawful attempt to deny red foxes the habitat protections they need.”

The Sierra Nevada red fox is one of North America’s rarest mammals. In 2011 the Center petitioned the Fish and Wildlife Service to protect the foxes under the Endangered Species Act and designate critical habitat. In 2021 the Service listed the Sierra Nevada distinct population segment, centered around the Sonora Pass area, as endangered but declined to designate any critical habitat.

The Center challenged that decision in December 2024, saying the Service’s refusal to protect critical habitat ignored threats to the fox’s habitat and failed to consider its long-term recovery.

In today’s ruling U.S. District Judge Dale Drozd agreed, emphasizing that the Endangered Species Act is intended not merely to keep endangered animals alive, but to restore them to healthy populations. The foxes have been lost from most of their range in the Sierra Nevada and need additional protected areas to truly recover.

The judge also found that the Service applied a test not found in the Act for determining whether critical habitat is “prudent,” requiring that habitat destruction be a significant threat before designating protected habitat. The judge said this improperly broadened what Congress intended to be a narrow exception to the general requirement to designate critical habitat. In either case, the foxes face a number of threats to their habitat, including snow mobiles, livestock grazing and climate change.

“Critical habitat is one of the Endangered Species Act’s most important safeguards because animals and plants can’t recover if the places they depend on disappear,” said Segee. “This ruling makes clear that the government can’t turn the law on its head by demanding that habitat threats cross some invented threshold before endangered wildlife get the protections Congress intended.”

The court also found that the Service failed to balance the benefits of designating critical habitat before deciding it wasn’t prudent, as required by the Act.

Today’s order directs the Service to draft a new critical habitat determination for the fox.