In 2017, a wildfire raged across a drought-sick mountain in Southern Arizona and nearly wiped out a subspecies of red squirrel found nowhere else on the planet.
In the aftermath of the Frye Fire — which destroyed a large swath of forest on the mountain — only 35 Mt. Graham red squirrels survived in the wild.
“Apocalyptic is the right word,” said Holly Hicks from the Arizona Game and Fish Department. “It was a devastating moment for all of us.”
“We’re almost 10 years post-fire, and we still don’t see much of any sort of tree regrowth,” Hicks said. “The habitat is just making a turn, and for better or worse, it’s not squirrel habitat any longer.”
Long before the 2017 fire, a barrage of stressors had pushed the squirrel to the brink. Listed as endangered since 1987, intense drought, warmer temperatures, insect outbreaks and decades of fire suppression led to a “firestorm of sorts that can really take out a good amount of habitat,” said University of Arizona researcher Bret Pasch.
Pasch and Hicks are part of a team of scientists and government agencies working to stabilize the number of Mt. Graham red squirrels. In December, the annual population count found 232 of them lived on the mountain.
The escalator effect on Mt. Graham
Mt. Graham is a peak in the Pinaleño Mountains that towers over the desert floor in Southern Arizona.
At its base, thorny mesquite trees and barrel cactus cling to its slopes. But the steep ascent quickly gives way to oak and juniper. Higher still, ponderosa pines take root. Near the 10,720-foot peak, stands of Douglas fir and Engelmann spruce provide critical habitat for the endangered squirrel.
Mt. Graham is known as a sky island, a mountain ecosystem surrounded by a “sea of desert.” Its isolation makes the Mt. Graham red squirrel more vulnerable. It can’t find suitable habitat by going down the mountain, and eventually it can’t go any higher either. This is known as the escalator effect.
“As climate warms,” Pasch said, “species will be increasingly pushed up to the top of the mountain, and then eventually lost.”
Warming temperatures also affect the food supply. When a squirrel eats the seeds from a cone-bearing tree, mounds of the shredded cones build up over time. The piles of material are known as middens, and Pasch said the animals will stash food there for long-term storage.
Middens are like a forest refrigerator. With climate change, “the refrigerators are kind of busted,” raising the risk that the stashed cones will dry out or spoil, Pasch said.
‘We’ve been trying so long’
Far from the mountaintop, a team of biologists at the Phoenix Zoo has been trying to breed captive Mt. Graham red squirrels since 2014.
It hasn’t worked.
“We’ve been trying so long,” said Conservation Director Tara Harris, who keeps the animals in a cozy walk-in enclosure that’s stuffed with discarded Christmas trees.
When the squirrels first came to the zoo, Harris said her team was warned that the females would only be receptive to mating on a single day each year. They were also told the animals were so territorial that they couldn’t be put in the same cage because they might kill each other.
That has turned out not to be true.
Harris said in captivity, when there’s enough food available, the animals love to be around each other. Given the chance, they even snuggle together in the nest box and groom each other like primates. But that hasn’t yielded any new babies.
“They just keep throwing us for a loop,” she said.
Scientists have banked DNA samples just in case the population crashes again. In the worst-case scenario, cloning new animals is a possibility.
The outlook may sound bleak, but the number of endangered squirrels on Mt. Graham has rebounded to roughly what it was before the fire, according to the Arizona Game and Fish Department
Hicks from the Arizona Game and Fish Department said controlled burns have reduced the fuel available for future wildfires. Some trees are tagged with pheromone packets to keep the insects away.
“What’s the point of getting into this work,” Hicks said, “if you’re not going to be an optimist?”
And for now, the squirrels that remain do what they can to persist. Pasch points to the stump of a dead tree where a young male nibbles on the cone of an Engelmann spruce.
It’s a privilege to see one in the wild, he said. “It’s like a diamond, you know. A precious jewel. It’s our heritage. I feel like if you give them a little bit of a chance — some forest and enough food — they’ll figure it out.”
This article was originally published on WBUR.org.
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