For a few moments, the squirrel sat rock-still on the edge of a pine bough inside the wire cage, a carrot chunk clutched in its paws. Then, someone in the room moved.
The animal, a year-old Mount Graham red squirrel, launched itself at the top of the cage and skittered around the wire walls until it found a spot on another branch.
"They do that sometimes when they get stressed," said Tara Sprankle, conservation manager for the Phoenix Zoo. "They just race around in circles until they calm down."
There are nerves on both sides of the cage. The squirrel and three others in nearby enclosures are not only members of an endangered species, they are among the last remaining 214 Mount Graham red squirrels left in the world.
They were brought to the zoo's conservation center amid concerns that their isolated habitat in southern Arizona's tinder-dry Pinaleņo Mountains could be wiped out by wildfire, driving the entire subspecies to extinction.
"If there were a big fire, we could be working with the last of these guys anywhere," said Stuart Wells, the zoo's conservation and science director. "So, yes, we were a little nervous. But I think we're all adjusting well."
Wildlife biologists captured the four squirrels - two males and, if luck holds out, two females - and took them to the zoo in late June under an emergency order by the U.S. Fish and Wildlife Service, which oversees imperiled species.
The agency decided the threat of wildfire this year was serious enough to warrant collecting the individual squirrels as a sort of insurance policy on their survival. Wildfires in 1996 and 2004 burned thousands of acres of squirrel habitat in the Pinaleņos, losses that likely pushed the population numbers of Mount Graham red squirrels lower in recent years.
Fish and Wildlife designated the squirrels at the zoo a "refugium population," a term that describes a group isolated to preserve the genetics of a species in the event the wild population is lost.
The squirrels could be released back into the wild later this year, or they could remain at the zoo as part of a separate pilot project to breed the animal in captivity, with the goal of someday rebuilding the population.
"The zoo has a legacy of involvement in native-species conservation efforts," Wells said. "We're honored to be entrusted with these species."
The Mount Graham squirrel is a subspecies of the more common red squirrel. It lives in the pine and mixed-conifer forests of the Pinaleņos, part of southern Arizona's high-elevation Sky Islands ecosystem.
Their population has fluctuated over the years, from about 140 in the 1980s to more than 560 in the late 1990s. Their numbers have declined over the past decade, in part, scientists say, because habitat has been lost to drought, insect attacks, wildfire and development.
A 1997 Fish and Wildlife study found that the squirrel was at significant risk of extinction as its numbers dwindled, although researchers have not agreed on how low a number would signal irretrievable loss.
Environmental groups say one of the biggest threats to the squirrel is the University of Arizona's Mount Graham International Observatory. The buildings and the access roads have fragmented habitat and led to fire-suppression decisions that expose the forest to rarer but larger blazes, the groups say.
Federal officials are reviewing many of those issues as part of a revised recovery plan, but the emergency order issued in June shifted the immediate focus to simply avoiding an ecological disaster.
The first challenge was capturing the squirrels, said Marit Alanen, lead biologist for Fish and Wildlife's Mount Graham squirrel program. She worked first to condition the animals to eating the bait, putting out nuts and peanut butter without a trap. Once the squirrels knew about the food source, traps were laid out.
"This is also not a great time of year to capture females because a lot of them are either pregnant or nursing," Alanen said. "The last thing I wanted to do was remove a nesting female. I was nervous. I didn't want to be the cause of anything bad happening to them."
After about 10 days in the field, Alanen had captured four squirrels, two males and, it appeared, two females, though zoo biologists still can't make a final confirmation because one of the two believed to be females is just a few months old.
The zoo was waiting for a decision on its captive-breeding project when Fish and Wildlife issued its emergency order. The zoo's conservation center has helped breed and release other native species, including the California condor, the Mexican gray wolf, the black-footed ferret and the Chiricahua leopard frog.
In a nearby room, the zoo is caring for refugees from the Wallow Fire, which burned more than half-a-million acres in the White Mountains. More than 800 tiny, endangered Three Fork springsnails were fished from springs and cienegas and will remain in tanks at the zoo until water quality improves in their native habitat.
To prepare for the squirrels, workers modified four ferret enclosures; long, rectangular cages with attached boxes big enough for nesting. Vertical space was added to give the squirrels room to climb, and the pine boughs were fitted inside.
Diet still is a work in progress. So far, the menu has included nuts, fruit, pine cones, vegetables and a pelletlike "rodent block."
"We have to work out a caloric intake," said Wells, the zoo official. "They may not have the same activity level as in the wild, so they probably shouldn't eat as much. We're trying to find a good balance."
The squirrels will remain isolated from each other for now, partly because they're so aggressive and territorial.
If Fish and Wildlife approves the captive-breeding project in the next few months, the squirrels now in residence could remain; if not, they will be released later this year, after any fire danger subsides.
Captive breeding will be complicated at best. The window for female squirrels to mate is less than a day each year, as short as six hours, Wells said. The zoo will rely on research from other scientists, including a team at UA, if the long-term program moves forward.
"Right now, we don't know how to breed them in captivity," Alanen said.
"It's the first time they've been taken out of the wild, and any time you take an animal into captivity, there are risks. But there was also the potential to lose so much."
A red squirrel from Mount Graham is seen at the Phoenix Zoo.
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