A regional director at the U.S. Fish and Wildlife Service ordered agency biologists to withdraw a proposed rule that would list wolverines as a Threatened species under the U.S. Endangered Species Act, according to a memo leaked this week. That May 30 document, leaked Monday by the Center for Biological Diversity, shows that Director Noreen Walsh doubts climate change's affect on the species.
North American wolverines rely on persistent deep snow for the dens in which they bear young. USFWS had been preparing to list the predators as Threatened due to the likely impact of climate change on the 300 or so remaining animals in the contiguous United States, mainly in the Cascades and North Rocky Mountains.
"I do not believe that climate change poses a threat to wolverine or its habitat in the foreseeable future such that the wolverine warrants listing under the ESA," wrote Walsh in the May 30 memo.
Walsh is the Director of USFWS Region 6, which covers eight western states from Montana and North Dakota south to Utah, Colorado, and Kansas. As the wolverine ranges into other USFWS regions, she writes, she consulted with those regional directors before penning the memo, including Alexandra Pitts, whose Region 8 includes California. "[T]hese Regional Directors do not support ... adding the wolverine to the list of threatened species for reasons similar to my own, including a concern about the degree to which we can reliably predict impacts to wolverine populations from climate change," Walsh writes.
Wolverines are the largest members of the weasel family and are renowned for their ferocious nature, as well as the rapacious manner in which they feed. The North American wolverine, Gulo gulo luscus, is considered a distinct subspecies, distinct from the wolverines that inhabit boreal parts of Asia and Europe. USFWS proposed listing the North American wolverine as a Threatened species in February 2013, but delayed its final decision, originally due in February 2014, in order to obtain more public comment on the issue. That move was widely seen as bowing to pressure from the state governments of Montana, Idaho, and Wyoming, which charged that the climate models USFWS used to predict less snowpack weren't detailed enough to ensure that every single spot ever used by a wolverine for denning would suffer diminished snowpack.
Walsh seemingly acknowledges charges that USFWS bent under pressure from the states in her memo:
[W]hile state agencies are our primary partners in conservation, the determination I have come to as stated in this memo about the wolverine's status under the Endangered Species Act is mine alone, and has not been influenced in any way by a state representative.
The alleged uncertainty about the precise effects of climate change on wolverine habitat is the primary reason Walsh gives for her directive to withdraw the wolverine as a candidate for Threatened species status. Nonetheless, her memo admits a strong consensus among biologists consulted by USFWS that lack of deep snowbanks is a deal-breaker for wolverines considering breeding. Wolverines generally require snowbanks five feet or more in depth that last until mid-May in order to build their breeding dens.
Walsh cites less certainty about whether wolverines are absolutely tied to deep snow for other life habits, such as hunting. The animals' broad, fur-covered feet act like snowshoes, allowing wolverines to move quickly in deep snow. That's a serious advantage over some of the wolverines' larger prey such as deer and elk, which can become mired -- and tired -- in deep snow.
That said, wolverines can still hunt without snow, and in any event, carrion tends to make up a major portion of the wolverines diet, with small animals making up much of the remainder. But even if wolverines can feed themselves in the absence of snow, you'd think the catastrophic effect of losing breeding habitat would be enough to fear for the wolverines' survival. But as Walsh writes in her memo, mere potential inability to breed isn't enough to persuade her that the wolverine merits listing:
As discussed in more detail above, it is my best professional judgment we can only reliably predict a commensurate decline in wolverine habitat if we believe that wolverine [sic] have an obligate relationship with snow for all life stages. While there seems to be general agreement that wolverine [sic] are closely associated with snow for denning, there is far less agreement about the need for snow to persist specifically until May 15 or contiguous snow over an individual wolverine's home range as well as across the range of the species.
Walsh also contends that three wolverine sightings in recent years, including a well-publicized camera trap capture in California's Tahoe National Forest in March 2008, indicate that the North American subspecies may well be expanding its range. The other sightings include one in Colorado in 2012 and a sighting this April in Wyoming's portion of the Uinta Mountains. Though all three sightings were in places where no wolverines had been documented for decades -- the most recent previous California sighting took place in 1922 -- that's still three single animals in three far-flung states cited as evidence of an expanding range for the wolverine.
That's not implausible on the face of it, as wolverines are notoriously reclusive, and maintain extremely low population densities over broad ranges. But it's still much more tenuous evidence than Walsh seems willing to accept when it comes to modeling the effect of climate change on snowpack. And her citation of the California sighting, at least, goes against her own agency's formal statements. In its February 2013 proposal to list the wolverine, USFWS wrote:
In 2008, a male wolverine was discovered in the Sierra Nevada Range of California, the first verified record from California since 1922... Other wolverines may have travelled to the Sierra Nevada and remain undetected. There is no evidence that California currently hosts a wolverine population or that female wolverines have made, or are likely to make, similar dispersal movements.
Environmentalists are charging that Walsh's secret memo is more evidence of political interference in the science of wildlife conservation. "The decision to overrule agency scientists and deny protection to the wolverine is deeply disappointing and shows that political interference in what should be a scientific decision continues to be a problem under the Obama administration, just as it was under George W. Bush," said Noah Greenwald of the Center for Biological Diversity. "Wolverines and the winter habitats they depend on are severely threatened by our warming world. Only serious action to reduce fossil fuels can save the wolverine, tens of thousands of other species, and our very way of life."
A final rule is expected in early August.