The Mount Graham red squirrel faces "a significant risk of extinction," according to a University of Arizona biologist who monitors them.
A captive-breeding program is being contemplated to head off that possibility.
The most recent squirrel count found about 250 remain, a population about the same as in 1987 when the squirrel was first listed as an endangered species.
Since that time, most of the squirrel's preferred habitat, the Englemann spruce forest that surrounds the telescopes in the highest peaks of the Pinaleños, has disappeared.
About 80 percent of the mature spruce trees succumbed to successive waves of insect attacks and fire, aided by a 10-year regional drought.
Younger trees put out more pine cones after fire, said John Koprowski, who heads the UA's squirrel-monitoring program, but they do so in a sparser forest that leaves the squirrels vulnerable to avian predators. The red squirrel shares the mountain with goshawks and Mexican spotted owls - two threatened species.
The habitat and the squirrels have been "amazingly resilient" over the centuries, Koprowski said, surviving periods of intense drought and catastrophic fires over the past 11,000 years.
"The red squirrels have probably been able to make it through a series of challenges in the past," Koprowski said, "but the pace at which it is happening at present is something that is really a new addition to their challenges."
Koprowski said the squirrels' fate "is in the hands of a number of people coming together with long-term plans to ensure we have quality habitat on the mountain."
One plan under consideration by the U.S. Fish and Wildlife Service would remove a small number of red squirrels to investigate the feasibility of a captive-breeding program at the Phoenix Zoo's conservation center.
"The numbers have gotten so small, and they don't exist anyplace else," said Stuart Wells, the zoo center's director of conservation and science. He said a program to breed red squirrels in captivity needs to be in place before the next catastrophe hits their habitat.
"Without some way of replenishing that population, they're going to be gone," Wells said.
The most recent fire on Mount Graham, the 2004 Nuttall Complex, directly killed up to 35 percent of the squirrels in the study areas that overlapped the burn, Koprowski said. Four of nine male squirrels and three of 11 females were missing after the fire. The three females were lactating, meaning their young also died as a result of the fire.
Restoration of squirrel habitat is a complex puzzle, Koprowski said.
Climate models for the region predict continued warming and possible drought, which could cause more fire and insect infestation, and affect the mix of trees on the mountain, he said.
Contact reporter Tom Beal at email@example.com or 573-4158.