PHOENIX — An endangered squirrel species’ estimated population has plummeted since a major wildfire burned much of its habitat atop a southeastern Arizona mountain last summer.
An annual multi-agency survey of the Mount Graham red squirrel produced an estimate of only 35 squirrels, which is only 14 percent of the 252 squirrels estimated in 2016, the Arizona Game and Fish Department said.
The Frye fire caused “unprecedented impacts” to the squirrel habitat, but they cautioned that they’re not sure whether their standard survey methods provided an accurate population estimate in severely burned areas, department officials said.
Surveyors observed squirrels where they didn’t live previously, officials also said.
Officials are considering steps to help the squirrel population’s chances for survival, the department said.
The species was declared endangered in 1987. Its population peaked at about 550 in the late 1990s, but it typically ranges between 200 and 300.
Mount Graham, a so-called sky island with a forest environment high above surrounding desert, is 70 miles (113 kilometers) northeast of Tucson.
Lightning ignited the Frye fire on June 7. It burned hundreds of acres of squirrel habitat and a total of about 76 square miles (196 sq. kilometers) of timber, brush and chaparral in steep, rugged terrain on and around Mount Graham.
Evidence of the wildfire was observed in 95 percent of the surveyed locations of squirrel habitat, with 80 percent showing at least some habitat loss and 44 percent being completely burned, the department said.
Steve Spangle, a U.S. Fish and Wildlife Service supervisor, said the fire damage to the squirrel habitat was “a textbook example of how species with low population sizes, especially those confined to a small geographic area, are vulnerable to natural events such as fires, floods, and severe drought.”
The survey’s population estimate comes from visiting middens, which are places where squirrels store pine cone seeds.
“Our current survey methodology does not account for squirrels that dispersed from fire impacted areas. Surveyors observed some squirrels in previously unoccupied areas,” Tim Snow, a Game and Fish Department wildlife specialist, said in a statement released by the department.
Given the fire damage to the habitat, Snow said, the squirrels’ ability to survive the upcoming his winter may be the key to their long-term survival.
Steps under consideration to help the squirrels include assessing the remaining habitat, reducing food and habitat competitors and supplemental feeding during the winter, Snow said.
Another census is planned next spring.
The 2016 estimated population of 252 squirrels was down slightly from the 2015 estimate of 263, and the state agency said last December it remained optimistic about the squirrel despite the slight reduction.
Other long-term threats to the squirrels and their habitat include insect infestations, competition with non-native squirrels, and poor cone crops caused by drought, the department said.
Coronado National Forest officials said in August said they plan to treat 300 acres of Douglas fir trees next spring to keep bark beetles from destroying the red squirrels’ habitat. Forest officials said then that the 2017 fire and one in 2004 burned a total of 1,330 acres (538 hectares) of squirrel habitat, leaving only 590 acres (239 hectares) of the habitat.