Pronghorn Most Endangered Species at Yellowstone
Copyright 2001 Reuters
April 3, 2001
By JEFF TOLLEFSON, Reuters
YELLOWSTONE NATIONAL PARK, Wyo.--With its unique dark horns, goat-like shape and world-class speed, the pronghorn antelope would seem to be on top of the world, but it is a very different story with the herd at Yellowstone National Park, where the population is mysteriously dwindling.
Experts say the pronghorn is in more peril of extinction than any other species in Yellowstone, the first national park, where nearly 3 million people visit each year.
"To anybody that is a serious Yellowstone-watcher, you've got to be concerned about the long-term survival of these pronghorn," said John Varley, director of the National Park Service's Yellowstone Center for Resources.
Last year's count tallied only 209 pronghorn in the herd, down from nearly 600 about 10 years ago. Park scientists do not know why the population is down and are conducting studies in an effort to gain more insight.
Generally antelope favor open areas where they can take advantage of their speed and keen eyesight, but the pronghorn in the park traverse rugged terrain where they are vulnerable to lurking predators.
"They have a long migratory path. They swim the Yellowstone River and go through forests, things that pronghorn are not expected to do," Varley said.
Pronghorn antelope can be spotted in the northern part of the 2.2-million-acre park from around Mammoth Hot Springs to the Lamar Valley, popular as a wolf watching area.
YELLOWSTONE HERD CUT OFF FROM HERDS IN NORTH
Citing the dwindling numbers, complex migration routes through forests and rivers and development that has largely cut the herd off from its cousins to the north, wildlife biologists fear the worst is possible for this distinct group.
They say that even if other pronghorn were introduced into the park they might not be able to learn quickly enough the current herd's unique habits to be able to survive.
"The most endangered population here is the pronghorn, hands down," Varley said, but he added it is hard to generate concern because the pronghorn remains a common sight in the rest of Wyoming and surrounding states.
This ungulate is anything but ordinary. Both sexes have the distinct prong-shaped horns and they are unique among antelopes in shedding their horns annually like antlered deer and elk.
Weighing some 90 to 125 pounds (40 to 56 kg), the pronghorn is built for speed. It can sprint at 55 miles (88 km) per hour, bested only by the cheetah, but its speed cannot be matched by any other creature in the distance run.
A large heart, lungs and windpipe allow for unparalleled stamina. With keen vision on the open plains, adult antelope are well prepared to elude predators. Hardiness in the face of desert heat and brutal cold allow the antelope to make its home from the plains to the rugged country of northern Yellowstone.
Numbering almost 600 in 1991, the Yellowstone pronghorn dropped to 235 in the 1995 spring count, according to park officials. But what has wildlife biologists baffled is that the population has not rebounded.
SCIENTISTS TRACK RADIO-COLLAR DOES
Researchers are currently tracking does with radio collars in two studies regarding fawn survival and habitat use, especially on the pronghorn's winter range.
The antelope spend the summer in the Lamar Valley, where reintroduced wolf packs reign, and winter in the Gardiner Basin, where the Yellowstone River flows north from the park.
Although wolves kill an occasional antelope, the park's top carnivore generally sticks with meatier elk to feed an entire pack, according to Bill Edwards, an instructor for the Yellowstone Association Institute.
Although the coyote is the usual suspect, being the main predator of the antelope, researchers note that the coyote population has dropped by roughly 50 percent in the northern part of the park since the wolves were reintroduced in 1995.
For the past 10 years conservationists and wildlife agencies have been working to protect winter range north of the park for antelope, elk and other species. But, scientists say, even with sufficient winter range the herd remains largely cut off from antelope grazing on the plains farther north.
With a large, healthy population that might not be a such a problem, but a lack of genetic diversity and the occasional ecological hardship can seriously threaten small herds.
"It would appear that this is an isolated population that is following established migration and movement patterns that are very old," park wildlife biologist Glenn Plumb said.
"With this low of a population, if we lose those movement patterns, would we ever be able to reestablish the knowledge of the pronghorn for the landscape? Unlikely."