Blane Klemek column: Winter dens of bears vary
The American black bear makes Minnesota its home. Yet seeing a bear in the northern forests is a rare event. Even rarer than observing a black bear going about its business, is seeing one in the wintertime.
Commencing around late October into November, black bears sleep through the long and frigid winter months in a variety of interesting and secretive places. Several months later, normally by late March into April, black bears awaken and emerge from their dens.
It wasn't long ago that I wrote in a similar column that, "as much time as I've spent in the woods, I have not knowingly come across an authentic bear den." I wrote that I believed I had found likely bear dens or den sites, but had never actually seen one in use by a sleeping bruin or had determined with certainty the den's past occupant. All of that changed this past March.
I was lucky enough to visit an active bear den while observing and assisting DNR bear research biologists Dave Garshelis and Karen Noyce with locating a radio-collared female bear and her three cubs. Our primary task was to find the bear den and replace the sow's old radio collar with a new one.
Needless to say I was thrilled with the experience of not only handling the 175-pound, 11-year-old female black bear, but also in helping with recovering her sleeping yearling cubs from the den. But what was also very interesting to me was the den that the sow had chosen for the four of them to sleep in. It was about as comfy a den as any bear den could possibly be.
The den was a hollow "root wad" of a wind-thrown balsam fir tree. An adjacent tree that the fir tree struck when it originally blew over prevented the balsam from completely reaching the forest floor. Consequently, the balsam's roots did not rip out of the ground to create the classic ground depression that a wind-thrown tree's roots typically leave behind. In the case of this tree, the balsam fir, its roots remained bound in the soil and, instead, a cavity was formed within.
It's hard to say how the sow discovered this particular den. If it wasn't for the entrance hole, which of course she herself could have excavated (or by perhaps even another animal such as a fox, coyote or wolf), the mound of earth at the base of that nearly toppled fir tree would hardly be discernible. I wondered while peering inside the bear den with a flashlight, "How did she know the root wad would make a good den?"
I was surprised by the relative comfort of the bear den's interior. I wish now I had crawled inside to see just how comfortable it really was, but it wasn't difficult to tell. The interior of the den was completely dry and its floor was covered with dry grasses that were evidently put there by the sow.
The dimensions of the den were tight, no larger than 4-feet-by-4-feet, probably smaller, and was between 2 and 3 feet high. Its entrance hole was small as well, scarcely big enough for an average man to fit through. It was obvious to me that the bear den, with four bears sleeping snuggly inside, was a safe, warm and dry place to spend the winter.
Wildlife research biologists have shown that black bears hibernate in a variety of different dens. In a Southern Appalachian study, researchers monitored 31 bears for 39 "bear winters." Forty-one percent of chosen dens were live trees; rock cavities made up 32 percent; excavations equaled 14 percent; snags (dead trees) 8 percent; while ground nests totaled 5 percent of chosen den sites.
In a 10-year Wisconsin black bear population dynamics study conducted from 1984-94, researchers concluded that of 50 dens visited and 133 bears monitored, 34 percent utilized full excavations; 26 percent of the bears used brush piles; 17 percent made use of partial excavations; 9 percent utilized rock caves; and 4 percent used hollow trees and other types of dens. Minnesota black bears choose comparable dens and den sites as Wisconsin black bears.
Additional Wisconsin black bears of recent times have even made the news. In 2004, it was reported that a slumbering black bear was observed inside a bald eagle nest. It was later confirmed by a Wisconsin DNR wildlife biologist that a young black bear was curled up inside the bowl of an eagle nest on top of a 45-foot aspen tree.
The mystique of a bear den captivates the imagination of us all. A quick Internet search reveals that the mere term "bear den" is used in ways that probably have nothing to do with a real bear den at all; from Bear Den Campground to Bear Den Golf Course to Bear Den Landing to Bear Den Mountain and more.
Nevertheless, we all know that since plenty of black bears live throughout Minnesota's North Country, then bona fide bear dens must also exist as we get out and enjoy the great outdoors.
Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife. He can be reached at firstname.lastname@example.org.