In Mongolia railroad lines prevent gazelle migration, while North American highways act as a barrier for brown bears, and hydroelectric dams in Canada stymie woodland caribou.
For pronghorn, winter migrations take about two to three days with the animals traveling 30 miles (48 kilometers) in a day.
Spring migrations follow the melting snow and can take as long as a month for all the animals to finish the journey.
The pronghorn at one time had eight different migration routes that allowed them to travel from Grand Teton National Park to just north of Yellowstone National Park (take a virtual tour of Yellowstone).
Now only two of these routes remain, and both paths include bottlenecks that vary from 328 to 2,000 feet (100 to 610 meters) wide.
One of these, the bottleneck at Trapper's Point, was once 6,562 feet (2,000 meters) wide before development slimmed it down.
Oil Spread
Takehito Ito is a scientist at the Arid Land Research Center at Tottori University in Japan who was not involved in the study.
Narrow bottlenecks "are obviously the priority areas for conservation of the pronghorn population," Ito said. "But the area is outside of the national park."
This study, he continued, "shows the inadequacy of current conservation strategies and the necessity for larger protected areas."
The spread of the oil and gas industries in the region is a looming conservation issue, WCS's Berger says. (Read about the natural gas boom in the U.S. West in National Geographic magazine [July 2005].)
"The rate of housing increases at the southern terminus of the migration route is in direct proportion to the number of gas wells that are being drilled," Berger said.
"With more people, there is more habitat loss, and unless some safeguards are put in place, Wyoming's wildlife will lose."
But the problem is not difficult to solve, Berger says: People need to protect and conserve the land along the pronghorn's path.
"When migration routes are not predictable, it's less clear what land to protect," he said.
"But in the case of the pronghorn it's easy, since the route is invariant and apparently has been that way for some 6,000 years."
Editor's Note: Joel Berger has received a number of research grants from the National Geographic Society. National Geographic News is part of the Society.
Free Email News Updates
Sign up for our Inside National Geographic newsletter. Every two weeks we'll send you our top stories and pictures (see sample).
|
SOURCES AND RELATED WEB SITES
|
