Arizona’s Pronghorns Making Comeback
TUCSON, Ariz. — About 2 1/2 years ago, the survival chances for Arizona’s endangered Sonoran pronghorns were grim. Victimized by prolonged drought, only an estimated 21 of the sleek desert-dwelling animals were left in this country; their extinction appeared inevitable.
But today, after above-average winter rains, a favorable spring and initial success from a recovery program including semicaptive breeding, forage enhancement and emergency water supplies, the shy creatures are making a comeback. Their numbers were estimated at 58 before numerous springtime births.
“This is really exciting, because it looks like they’re on a roll,” said Mike Coffeen, coordinator for the U.S. Fish and Wildlife Service’s Sonoran pronghorn recovery team at the Cabeza Prieta National Wildlife Refuge.
“But it’s weather-dependent,” he cautioned, “so keep your fingers crossed.”
The next few months will be crucial to survival of fawns born between February and April – and to the population’s near-term growth.
“If the (summer) rains come early enough we’ll have tremendous fawn survival,” said John Hervert, Sonoran pronghorn specialist with the Arizona Game and Fish Department. “If they don’t come till late August-September, fawn survival could be low.”
Coffeen estimated that the recovery effort has cost $1.5 million, principally from the Marine Corps, Air Force and Arizona Game and Fish. The military services use the Barry M. Goldwater Range for aircraft training missions and use spotters to ensure that no pronghorn are present.
The fawns are vulnerable to dying before summer’s first rains, but even more so within their first few weeks of life, until they’ve learned to run, Hervert said.
“After one week, they can outrun the fastest human,” he added.
Within a month, they can outdistance their principal predators – coyotes, mountain lions and bobcats.
The goat-sized animals, resembling deer in build with eyes able to detect distant movement like binoculars, are capable of speeds approaching 60 mph.
Nearly 140 of the genetically distinct breed, often mistaken for antelope, roamed some 2 million acres of Arizona’s vast western deserts, including the 60 mile-wide refuge and the Goldwater Range, before the drought’s grip tightened in 2001 and 2002.
The only other population is found in Sonora, Mexico, where there are estimated to be more than 600, an all-time high.
Biologists don’t know how many fawns were born or have survived this spring in Arizona. For now they’ve given up netting the animals from helicopters to fit them with radio collars because it’s traumatic for the skittish, elusive animals.
“The population was so low that we felt risking lives of animals with capture was uncalled for,” Hervert said.
But they’re optimistic that births were plentiful this spring, both because of a wetter-than-usual winter that produced abundant forage and based on first-ever births at a square-mile captive breeding enclosure on the refuge. Ten fawns, six of them females, were born to six females, and all remain alive.
Within about a week, the recovery team also will have its fifth functioning forage enhancement plot – three on the Cabeza Prieta, two on the southern edge of the Goldwater range.
Each 3- to 6-acre parcel is irrigated with well water to spur growth of shrubs, palo verde and mesquite trees and grasses the pronghorns feed on in areas they frequent during the summer, when 110-degree temperatures are common.
“We’re not talking agricultural fields,” said Coffeen. “We only water when it starts to dry or we want regrowth.”
Use of the wire-fenced enclosure started in December 2003; it also has two exterior sets of electric fencing to startle potential predators.
A few of the males born this year likely will be released in 2007, Coffeen said, and the breeding males will be rotated for genetic diversity, either with a wild pronghorn to be captured or from fawns that officials hope to acquire from Mexico.
The last aerial count was conducted in December, an intensive, exhausting effort costing about $30,000 and involving several airplanes flying grids for six days, each manned with two observers staring at the desert floor.
Because of the costs, the next survey won’t be conducted until December 2006, Coffeen said.
Hervert is pleased with the pronghorns’ progress.
“We keep praying for good weather and we keep working hard to make sure the projects on the ground, the forage enhancements and water, are available,” Hervert said.
On the Net:
Defenders of Wildlife_Sonoran Pronghorn: http://www.defenders.org/wildlife/pronghorn/overview.html
National Parks Conservation Association: Rare and Endangered Sonoran Pronghorn: http://www.npca.org/magazine/2004/summer/rare_endangered.asp