Studies conducted in Banff and Yellowstone National Park, seem to indicate that grizzly bears may be heading into the dens later, and emerging earlier, than ever before because of climate change...........Additional research shows that bears in the Rocky Mountains of Alberta spend, on average, 41/2 months of the year in or near their den sites, which tend to be in the subalpine..............Grizzly bears almost always dig their own dens, but, on occasion, they will use a natural chamber such as a cave or hollow tree........ They typically dig a tunnel that opens into a slightly larger chamber............. Dens are often in places where the entrance is sheltered from strong winds and where deep snow will accumulate, providing extra insulation from the cold

Grizzly bears expected out of dens soon

globalbc.ca

Large male grizzlies are expected to emerge from their winter's slumber at the usual time in the coming weeks.

Photo Credit: The Calgary Herald ,

Grizzly bears in Banff National Park went into their dens earlier last fall than in recent years — but large male grizzlies are expected to emerge from their winter's slumber at the usual time in the coming weeks. 

Parks Canada officials say male bears usually begin to emerge in mid to late March, though there was a verified sighting of a grizzly bear by park staff on the train tracks between Banff and Canmore in January.

There has been speculation the warmer weather of the last two months may cause bears to emerge a little earlier, but a massive snow dump earlier this week may encourage them stay in for just a little longer.

"The important thing is we're headed into a time now where we fully expect to see the first of the large male grizzlies emerging from their dens," said Steve Michel, a human-wildlife conflict specialist with Banff National Park.

Parks Canada was able to nail down the exact dates 11 grizzly bears went into their dens last fall, because the bruins are fitted with high-tech GPS collars as part of a project to reduce bear deaths on the railway tracks.

Michel said both male and female bears went into their dens in fall much earlier than they have in recent years, noting denning patterns vary from year to year depending on environmental and physiological factors.

He said bear No. 64, the matriarch bear of the Bow Valley with her three offspring, was the first female in the den Oct. 12, while the latest date a female denned was Nov. 9.

"Bear 64 denned one full month later than the previous year, and I've also seen her active with offspring as late as Nov. 25," said Michel. "There's quite a big range."

The earliest a collared male bear went into the den last fall was Oct. 30, while the latest date was Dec. 3. Bear 122 — the largest of the collared grizzlies at an estimated 700 pounds — went into his den Nov. 20.

"That's quite a bit earlier than what we've observed in the past," said Michel. "That's at least a full month earlier than we would have expected of him."

Previous research showed that bears in the Rocky Mountains of Alberta spend, on average, 41/2 months of the year in or near their den sites, which tend to be in the subalpine.

Grizzly bears almost always dig their own dens, but, on occasion, they will use a natural chamber such as a cave or hollow tree. They typically dig a tunnel that opens into a slightly larger chamber. Dens are often in places where the entrance is sheltered from strong winds and where deep snow will accumulate, providing extra insulation from the cold. 

The most recent GPS tracking data has also given researchers information on exactly where those collared grizzly bears have denned this winter — and Michel said bear 122 and bear 64 are practically on top of each other.

"He's our biggest male and she's got three young ones," he said. "I expect to see him out any time now."

Studies elsewhere, including Yellowstone National Park, seem to indicate that grizzly bears may be heading into the dens later, and emerging earlier, than ever before because of climate change.

Officials say the reasons for den entry and emergence depend on both physiological and environmental factors, noting patterns in den use will vary depending on the age of the bear and the local climate.

"Possibly, there's a long-term trend that's happening with climate change, but within that there's significant variability on a year-to-year basis," said Michel. "It's not a rule to say that every year we're seeing bears denning later here."

The first reported grizzly bear sighting of the year in 2012 was April 2. Other first sightings of the year were March 30 in 2011, March 17, 2010, March 24, 2009, March 16, 2008 and March 25 in 2007.

Cathy Ellis is a reporter with the Rocky Mountain Outlook