September 11, 2009--Pronghorn antelope tangle with a fence in Wyoming's upper Green River Basin in fall 2008.
Unable to hurdle the barrier, they're forced to squeeze slowly through or underneath the wire--or turn their backs on a 6,000-year-old annual trek. At 125 miles (200 kilometers) long, the migration is one of the longest among land mammals.
Last fall and spring, biologist and photographer Joe Riis, funded by the National Geographic Society's Expeditions Council, became the first to document the entire pronghorn migration on foot. The experience made clear just how arduous human-made hurdles--fences, roads, natural gas fields, housing developments--are making the journey. (Watch video of the pronghorn expedition.)
(The National Geographic Society owns National Geographic News.)
—Brian Handwerk
Three stragglers are part of a group of Grand Teton National Park-area pronghorn that began their annual migration late and were forced to deal with heavy fall snows in 2008.
When snow makes food sources scarce each fall, the herd heads through Wyoming's Gros Ventre Range toward plentiful sagebrush to the south.
From the air, the Gros Ventre Range looks like a formidable obstacle, but it's familiar ground for the migrating Grand Teton pronghorn herd.
Wyoming is home to half a million pronghorn--nearly outnumbering the human population. But much of the Grand Teton herd's migration route crosses human habitat, including housing developments.
For a perhaps surprising reason, residential developments were the biggest threat photographer Joe Riis saw as he walked the pronghorn route in fall 2008 and spring 2009. "Pronghorns hate being around dogs," he said.
Published November 11, 2009
Escaping encroaching snows farther north, pronghorn run south through Wyoming's Gros Ventre mountains on their annual fall migration in 2008.
Photographer Joe Riis's goal in fall 2008 and spring 2009 was to see the land through the "eyes of the pronghorn."
But pronghorn have tremendous vision and are not fond of strangers, so Riis set up motion-triggered cameras to capture pictures like this.
"I have to know where they are going to go in order to set up a camera trap," he said. "To do that, I have to walk with them and experience their migration path."
During the 2009 spring thaw, Wyoming pronghorn retrace their autumn steps (and splashes) to return to the Grand Teton National Park region.
Snowmelt causes rivers and creeks to run high--adding another obstacle to the already formidable gauntlet the animals must run to return to their summer home.
Published November 11, 2009
In Wyoming's Grand Teton National Park a day-old pronghorn fawn snoozes away a June day in 2009. Within a few days, the animal will be able to outrun a human. Adult pronghorns are among the world's fastest land animals, reaching speeds of about 53 miles (86 kilometers) an hour.
Newborns tend to literally lay low—the better to avoid predators—until they get their legs under them, photographer Joe Riis said.
Published November 11, 2009
Pronghorn Passage
A pronghorn, one of a herd several hundred strong, stands beneath the distinctive bulk of the Grand Teton mountain.
Photographer and biologist Joe Riis hopes to raise awareness of the animals' epic, ancient migration and to encourage action to protect it.
"It's pretty incredible, because it's happening right in the middle of the United States," Riis said. "It seems like this type of stuff is long gone, and maybe most of the long migrations are. But this one is [still going], and I think it's worth protecting."
Published November 11, 2009