Tuesday, March 30, 2010

Entering Bear Dens part of Statewide Study

Photo by Randall Thacker

Vernal -- Wildlife biologists found an encouraging sight when they visited a bear den near Vernal recently: two bears that were just cubs the year before were alive and doing well.
“When Kevin Bunnell first entered the den, we thought there was only one [yearling in the cave with its mother],” says Dax Mangus, wildlife biologist with the Utah Division of Wildlife Resources. “But then Kevin whispered an urgent, ‘get another dose ready. There’s a second [one].’”

The sow and her two one-year-old bears (called yearlings) were nestled in the back of a cave that was about 20 feet long. The biologists used a tracking device to find the cave. The device picked signals up from a radio collar the biologists placed on the female in August 2008.

“When we found her den in early March 2009, she had two newborn cubs-- a male and female,” Mangus says. “A year later, both are still alive and in good shape. We only got a good look at one, though. The den was extremely narrow. If we pulled the other bears out, we weren’t sure we could get them back in again!” Statewide survey

The survey these biologists conducted in the Ashley National Forest north of Vernal is part of a larger statewide project. Biologists in each of the UDWR’s five regions have placed radio collars on bears to determine their reproductive success and how many of their cubs survive.

The biologists find and enter the dens in late February and early March. They tranquilize the female and any yearlings she has. Then they check the bears’ health and gather biological data. They do not tranquilize newborn cubs.

“We’ve been monitoring four collared bears in this region and one that was originally collared in another region,” Mangus says.

“Checking on the bears might sound easy, since we know where they are. But it isn’t. The bear we checked last week looked easy on paper, but I think it was the [toughest] hike I’ve ever been on.

“And [checking] that one is nothing compared to its closest neighbor,” Mangus says. “This year, one of our collared bears is down in Ashley Gorge. We took a look from the air at its radio location. Reaching its den site would require a long trip by snowmobile, a hike of a mile or so on snowshoes to the edge [of the gorge], then roping up and rappelling down the cliff face before hiking through a boulder field [filled] with thick brush.” Because of the risks involved, biologists will not check the Ashley Gorge den this year.

Good results across the state

Justin Dolling, game mammals coordinator for the UDWR, says other biologists are also finding good bear survival this winter in other parts of the state.

“Cub survival is running about 90 percent so far this winter,” Dolling said on March 16. “We still have another week or so [before this year’s survey is done]. But so far, the biologists I’ve heard from [have told] me that 10 out of 11 cubs they checked last year have survived. And about 80 percent of the cubs Hal Black has checked on the Book Cliffs have also survived.” Black is a long-time bear researcher at Brigham Young University.

Dolling says their successful birth and making it through their first year of life means the yearlings north of Vernal are about two-thirds of the way to becoming healthy, independent adults.

“This spring, the sow will ‘kick the yearlings’ off so she can prepare for the upcoming breeding season,” Dolling says. “The habitat conditions the yearlings find as they venture out on their own for the first time will be a big factor in whether they survive and become adults.”

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