Forty head of bison have been spending some time on the island as part of an effort to bolster Utah's newest bison herd in the eastern part of the state.
The Utah Division of Wildlife Resources captured the animals in Southern Utah's Henry Mountains, where about 300 head of bison live on 240 square miles of open range, in January. Before releasing them in the remote Book Cliffs of east-central Utah, officials brought them to a handling facility on Antelope Island, where they were tested for tuberculosis.
When they arrived on the island, the bison were expected to stay for only a few days, but Mother Nature had other plans. Snowy conditions in the Book Cliffs have made roads in the region impassable and prevented their release so far, but officials hope to make the move in the coming weeks.
Despite below-average snowfall in Northern Utah this year, the snowpack on top of the cliffs is currently 140 percent of normal, said Dax Mangus, Book Cliffs biologist for the Utah Division of Wildlife Resources.
"We're still having record snowfall in that area," Mangus said. "We need some of that snow to melt before we can get on those roads."
However, the delay may have been a blessing in disguise, he said, because many of the bison brought to Antelope Island were underweight when they arrived.
"They're still on the island, but they're doing well," he said. "They were a little lighter than in years past. This allows us to feed them and get a little more weight on them, to bulk them up a little bit before we release them into the wild."
A mature male bison can weigh up to a ton but still run more than 30 miles per hour, so capturing and moving the animals can be a dangerous undertaking. To minimize the danger, DWR officials decided to capture only calves, cows and yearling bulls weighing between 300 and 800 pounds.
To capture the animals, DWR developed a capture plan involving the use of two aircraft: A fixed-wing airplane with DWR spotters finding the bison, and a helicopter used to physically capture and move the animals.
Once animals were spotted, the helicopter would close in, single out one animal and separate it from the herd, and fire a net over it from a specially designed rifle. After the animal became entangled in the net and fell to the ground, crews would move in to blindfold and hobble it for transport.
Each bison was then flown about 10 miles to the nearest road, where another team was waiting to transfer the animals into waiting horse trailers for transport to Antelope Island.
Mangus said it's always stressful for wild animals when they are captured and relocated, but with the success of bison relocation efforts so far, "we feel the positive outweighs the negative.
"Bison are pretty hardy, so they handle it pretty well. They adapt pretty well to domestication."
The animals have stayed in quarantine on the island while officials waited for blood test results to certify the bison were disease-free, which they were.
The Henry Mountains herd began in 1941, when state wildlife officials trucked three bulls and 15 cows south from Yellowstone National Park. The herd has since grown to more than 300 animals today.
The 40 bison captured last month will join an existing herd of about 50 in the Book Cliffs, where a herd was established in 2008 and 2009 with 14 animals donated by the Ute Tribe and 30 coming from the Henry Mountains.
There's no definite timeline for moving the bison off the island, as officials bide their time waiting for roads in the Book Cliffs to become passable again, but Mangus said optimism remains high for the success of the project.
"We think they'll adapt fine in the wild."