A Natural View

Some grizzly bears remained active well into December this year, but cold temperatures followed by abundant snow during the second half of the month should have hustled the last of the bears into their winter dens.

Animals that remain active and confront winter demonstrate their numerous adaptations to cold and snowy winters. Fresh snow builds up on the backs of bison and elk because their well-insulated winter coats prevent wasteful dissipation of their body heat to the environment. The massive heads of bison serve as snowplows to clear snow away from the grasses and sedges they consumer year-round.

The tracks of pine marten show how much larger these weasels' feet become each winter due to the new fur growing between their toes. Red fox and lynx add fur between their toes, too. Larger feet function somewhat like snowshoes to aid the animal in floating on the snow. Snowshoe hares always have large feet that in winter allow them to travel on top of the snow. The white fur of snowshoe hares consists of hairs filled with air instead of pigment, which keeps the hares insulated and camouflaged.

The ruffed grouse I surprised on December 26th may have spent the Christmas snowstorm snuggled into snow. Powdery snow, with lots of air for insulation, often becomes a temporary winter refuge for grouse.

Although most birds have departed the higher elevations of Greater Yellowstone, Brad Barth has seen noteworthy birds during his trips from West to Old Faithful, including three pied-billed grebes on the Firehole River on December 22nd and American tree sparrows near the Madison River on December 27th. Most pied-billed grebes vacate Greater Yellowstone in winter in search of warmer waters, while some American tree sparrows migrate here from Alaska and Canada for the winter. Brad has also seen several kinds of ducks on the Madison and Firehole rivers so far this winter: in addition to Barrow's and common goldeneyes and common mergansers, Brad's sharp eyes have observed northern pintails, American wigeon, gadwalls and ring-necked ducks.

For more neat bird stories, ask Bob Hamilton about the day a few weeks ago when he spotted seven bald eagles between West and Old Faithful. Bob said all but one of the eagles were adults, which is to be expected as sub-adult eagles are less likely to be found in Yellowstone in winter.

To witness the adaptations of wildlife and to experience sightings like Bob's and Brad's, it's time to put on our own store-bought adaptations and venture outdoors. A spectacular winter wonderland awaits us!

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