By Emilie Ritter
HELENA, Montana (Reuters) - A harsh winter has stranded more than 2,500 pronghorn antelope at Montana's Fort Peck Reservoir and nearly all are expected to die this summer, wildlife managers said.
Big game animals in many parts of the West are recovering from an unusually cold winter that killed many and left several hundred frozen antelope carcasses in open fields.
Pronghorn antelope have been hit hard in eastern and northeastern Montana, where wildlife managers have said this season's die-off looks to be the worst in 30-plus years.
There are an estimated 300,000 pronghorn antelope in Montana and already thousands have died across the state.
Biologists will not know exactly how devastating the winter season was for the animals until the state's Fish, Wildlife & Parks agency does its population estimate in July.
But the dire situation facing the antelope at Fort Peck Reservoir in remote northeastern Montana is an indication of the extreme weather the animals have endured this year.
The stranded antelope, which number between 2,500 and 3,000, are on the south side of the reservoir, after crossing the frozen Missouri River to get there.
The animals do not usually venture that far south, but they did this year in search of scarce food for grazing, said state biologists. Now, they cannot leave the area, because they are caught between steep cliffs and a vast expanse of water.
"There's bunches of antelope on the shoreline kind of wandering back and forth, maybe trying to swim a little bit then coming back -- because it's well over a mile across the reservoir," said Mark Sullivan, a biologist with Montana Fish, Wildlife & Parks.
World Wildlife Fund program manager Dennis Jorgensen has been monitoring the situation at Fort Peck Reservoir.
"We would see groups of 15 or 20 pronghorn trying to (swim) across and of those, one or two would maybe make it, the rest would turn back," he said.
Wildlife managers say there is nothing that can be done to save the stranded antelope, who are already beginning to die off, and by the end of summer the limited supply of food at the shoreline is expected to have dried up.
Any survivors that last until the winter could walk back across frozen water to reach open land.
This year, a record-breaking 108 inches of snow piled up in northeastern Montana, breaking the previous record of 70 inches, Sullivan said.
Antelope make an annual winter migration of up to 400 miles roundtrip, to escape inhospitable conditions in southern Canada and reach the warmer Missouri River Valley surrounding Glasgow, in northeastern Montana.
Montana game officials have worked with the World Wildlife Fund and researchers in Canada to find ways to preserve the antelope's prairie migration routes, and hopefully avoid situations such as that at Fort Peck.
Some solutions could include having area landowners open fences during migration, or creating structures for the animals to safely cross highways and train tracks.
In another sign the winter was particularly harsh for antelope, Montana officials plan to cut back on the number of hunting tags for antelope in northeastern Montana. Each tag can be used to kill one of the animals.
Biologist Kelvin Johnson of Montana Fish, Wildlife & Parks said managing the antelope and their habitat requires a delicate balance.
"You want to reach out and help every single one of them, but we can't -- and that's heart wrenching. The other part though is realizing this is wildlife, this is Mother Nature, and they in fact have been bred, they've evolved, to deal with these types of things," he said.
(Writing by Alex Dobuzinskis: Editing by Dan Whitcomb and Greg McCune)