The endangered Mount Graham red squirrel on the Pinaleño Mountains of southeastern Arizona is on the slow mend, with their numbers seemingly stabilizing a few years after crashing to an all-time low.
The latest numbers came out of the annual survey by the Arizona Game and Fish Department, the Coronado National Forest and the U.S. Fish and Wildlife Service. According to the report, the population size of the Mount Graham red squirrel now hovers at 232, whereas last year’s survey clocked an estimate of 234.
“It’s a good sign,” said Bret Pasch, the director of the Mount Graham Biology Programs and a researcher in wildlife conservation and management at the University of Arizona.
Even at a plateau, the trajectory of the rodent numbers is heartening, said the state’s department of Game and Fish, especially given that the past year has been a dry one for Arizona’s Sky Island habitats, where the squirrels reside. According to the department, the area has seen little to no rain or snow in the wettest periods of the year, during winter and spring.
The Sky Islands are isolated habitats on mountaintops tall enough to sustain species used to cooler climes, before the era of global warming that drove them to seek refuge at higher elevations.
Now, the same creatures, including the Mount Graham red squirrel, have run out of altitude to climb. So they cling to their isolated sanctuaries in the mountains, their habitats separated by gulfs of deserts and grasslands in the lowlands too hot for their survival. Soaring over 7,000 feet above the Sonoran Desert, the Pinaleños are the last remaining stronghold for the Mount Graham red squirrels.
The warming climate is just the backdrop to a suite of immediate threats that the Mount Graham red squirrel is already grappling with. Specifically, the endangered squirrels are threatened by wildfires, insect infestations in their conifer habitats and competition with invasive Abert’s squirrels. This year’s drought has also led to poor yields in pine cones on which the squirrels feed.
Various conservation efforts in the past few years have sought to bring back the Mount Graham squirrel from the brink. And now, the latest report shows that these recovery programs seem to be paying off, though the long-term fate of the squirrels is still too soon to say.
“It’s such a long road,” said Holly Hicks, the small mammal project coordinator at Arizona Game and Fish who was involved in the survey as well as species conservation in the last few years. “I always try to take things day by day.”
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Squirrels are ‘tiny warriors’ with many admirers
Robin Silver stands among the burn scars from the 2017 Frye Fire. The fire ripped through habitat for the Mount Graham red squirrel and caused population to drop as low as 35.
The Mount Graham red squirrel is one of 25 subspecies of the American red squirrel — and the one whose existence is the most precarious, given that they live confined to the old-growth conifer forests found exclusively on sky islands.
That’s what makes them a special part of Arizona’s ecological fabric. “I think of the mountain as a national historic landmark that reflects our deep history and the biodiversity of the region,” said Pasch, with the furry, fiesty squirrel at the heart of it all.
The pocket-sized creature has an outsize fan base among scientists and conservation groups, thanks to their personality and charm.
“They’re sassy,” Hicks said. “We all get so excited to get up on that mountain and do our surveys, and have them come down from the trees and bark and chatter at us.”
Despite their adorable appearances, Mount Graham red squirrels are tiny warriors, and the last century hasn’t been easy for the critters. In the 1950s, wildlife biologists thought that the species had gone extinct. But about a decade later, a few individuals were discovered, leading to their listing as a federally endangered species in 1987. At their heyday in the 1990s, Mount Graham red squirrel numbers peaked at 550.
A captive Mt. Graham red squirrels sits in an enclosure at the Phoenix Zoo, where it is part of a project to breed the imperiled species, with an eye toward returning some to the wild.
But it would have been too soon for wildlife groups to celebrate or slack off. In 2017, the lightning-triggered Frye Fire scorched nearly half of the squirrel’s home ground. From a tally of 252 squirrels the year before, the population size plummeted to a mere 35 individuals in the aftermath of the fire.
A flurry of population rescue programs followed, including tree planting to restore burnt habitat and winter supplemental feeding for the silken survivors. Conservationists also turned to a breeding initiative at the Phoenix Zoo that has been ongoing since 2014 in hopes of reviving the population, though the effort has yet to produce any offspring until now.
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New challenges for long-term survival
Still, the combined efforts proved effective. A year after the fire, the population doubled in size. In the intervening years, the population trend is still bucking upward, inching past the 100 mark in 2021 and staying clear ever since.
“In part, that’s because there haven’t been any other major wildfires on the mountain” since Frye, Pasch said.
The subsequent improvement over the years can also be partially attributed to a new and more accurate method of measuring the squirrel population size. Scientists usually estimate the squirrel population by counting middens, the species’ winter caches of conifer seeds and other food. Previously, agencies would survey already known middens on designated plots, but now, scientists take care to uncover new middens and include them in the count.
As global temperatures continue to rise and Arizona’s bouts with drought lengthen, Mount Graham red squirrels might face heightened challenges to their survival. Trees put out fewer seeds during warmer and drier seasons, which limits food availability for forest dwellers. Moreover, at higher temperatures, pine cones stored in middens, which act as a refrigerator, tend to spoil faster. Pasch’s research has shown that Mount Graham red squirrel populations tend to tank after anomalously warm years.
Yet, red squirrels also have a few tricks up their sleeves. After the Frye Fire, the Mount Graham survivors were quick to expand their footprint from their spruce fir forests and settle into other conifer trees such as white pine and Douglas fir. Pasch and his colleagues have observed red squirrels elsewhere adapt in the face of drought — instead of banking all their pinecones in one midden, these wily mammals can spread their stockpile across several middens all at once, preventing the catastrophic loss stemming from the folly of putting all eggs in one basket.
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According to Pasch, this diversified foraging strategy has allowed red squirrels in Mexico to thrive despite their habitats being squeezed by hotter, warmer climates.
Mount Graham’s brethren are also known to hoard in both these centralized and the scattered manners — perhaps they’ll put these tactics to good use as environmental conditions grow increasingly hostile.
For this reason, Hicks remains optimistic about the Mount Graham red squirrel’s future.
“When we were first working on them, we thought of them as being fragile,” she said. “To me, at least, especially after the Frye Fire, I find them to be much more resilient than we ever thought they could be.”
Shi En Kim covers environmental issues for The Arizona Republic and azcentral. Send tips or questions to shien.kim@arizonarepublic.com.
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This article originally appeared on Arizona Republic: Endangered Mount Graham red squirrel holds steady in annual census