By Susan Morse
Endangered species work can
be hard on optimists. The best prognosis for many imperiled species is life support – dependence on humans to make it in the wild.
In southwest Arizona, biologists are aiming higher. “I'm encouraged,” says Jim Atkinson, the U.S. Fish and Wildlife Service's Sonoran pronghorn recovery coordinator based at Cabeza Prieta National Wildlife Refuge. “If we enjoy the success going forward that we have been seeing, I think we might have
a chance to consider downlisting.” A chance, in other words, that the fastest land animal in North America, clocked at 60 mph, would be removed from the endangered species list where it's been since 1967.
That optimism reflects a dramatic about-face for a species almost wiped
out in 2002. That year, a severe drought reduced the entire U.S. population
of Sonoran pronghorn to 19 adults.
Since then, captive breeding and other emergency steps have raised the count of the skittish, goat-size desert animals to about 400. More than 250 of these are in the wild.
The Service can't claim sole credit. It's just one player in an effort involving five federal agencies, the Arizona Game and Fish Department and two zoos. But $253,000 in grants from the Cooperative Recovery Initiative gave the project a “critical shot in the arm,” Atkinson says, helping it establish a second pronghorn population at Kofa National Wildlife Refuge, to the north.
Over the past three years, 61 pronghorn have been moved from Cabeza Prieta Refuge to Kofa Refuge, first by helicopter and later by custom-game trailer. At both refuges, biologists feed and rear pronghorn in pens, fit them with radio collars and release them. Bi-monthly aerial surveys monitor pronghorn survival in the desert.
For a high-strung and fragile-looking animal, pronghorn are tough, able to withstand harsh desert conditions. But habitat shrinkage – Sonoran pronghorn occupy less than one-tenth of their historic range – has thrown them a curve.
“They're a classic range animal,” capable of roaming 1 million acres for food and water, if unhampered, says Atkinson. “But the construction of highways and railroads and fences has taken away their ability to do that.”
To help compensate, project leaders have built more than a dozen wildlife water catchments. For pronghorn, these are lifesavers, since highways block their access to traditional water sources such as the Gila River in Arizona and the
Rio Sonoyta in Mexico. The catchments “seem to be getting pronghorn through the rough patch between the end of winter rains in March and the onset of summer rains in July,” says Atkinson.
The “giant cat-and-mouse game,” as he calls it, between smugglers and law officers along the U.S./Mexico border is another stressor. Human traffic
and vehicle traffic – trucks, ATVs and helicopters – are constants.
Acknowledging those disturbances, the Department of Homeland Security contributed $2 million in mitigation funds for Sonoran pronghorn recovery. The funds go through this fiscal year. “Our hope,” says Atkinson, “is to get remaining infrastructure put in before the funding runs out. And I think we will be there.”
Success won't be declared until biologists can keep pronghorn counts at or above target levels (225 at Cabeza Prieta, 150 at Kofa) for five out of seven years at three out of four pronghorn recovery sites. The other two sites are in Mexico.
Hopes are high, despite initial setbacks. At Kofa Refuge, most first-year releases perished. But second-year releases did better, including at least eight fawns
born in the wild. “I can't believe how well things have been going,” says Kofa Refuge biologist Christa Weise. “We have over 50 animals out there now,” she says, though rain was scarce in 2014-15. “We held
our ground even in a year with sub-par conditions.”
Susan Morse is a writer-editor in the Refuge System Branch of Communications.