Monday, December 06, 2010

Winter Wildlife Chronicles: Deer Diet

With the holidays approaching, many of us start to worry about running the gauntlet of tempting treats and massive meals that characterize so many celebrations. Come January, the gyms will be packed with those of us trying to shed those extra pounds we gained.

Let's be honest, though: Cookies, a full turkey dinner, or mug of hot chocolate are awfully comforting on a cold winter day.

And for good reason. Not so long ago in our evolutionary past, winter was a tough time. Losing weight was not a desirable outcome. Calorie-rich foods ensured survival.

It's still that way for mule deer. They need enough energy to make it through the long, cold winter.

At this time of year, mule deer move into valleys and low elevations (and even backyards, in the case of the one pictured above) to escape the heavy snow.

But to survive the winter, deer need nutritious plants. Cheatgrass, the non-native weed so common in foothills, has low nutrition value in the spring, when it is green. In the winter, it is worthless to wildlife, particulary when it's buried by a foot of snow.

Sagebrush, on the other hand, pokes out of the snow and is highly important to deer, elk, pronghorn, sage grouse and other wildlife.

Dr. Carl Wambolt of Montana State University reports that many big game species prefer sagebrush in the winter. One Montana study showed that sagebrush consisted of more than 50% of a mule deer's winter diet. A similar study for pronghorns found that sagebrush comprised 84% of their diet.

Other shrubs like bitterbrush, winterfat and salt brushes complement a mule deer's winter diet. Some biologists call bitterbrush "deer candy" because the animals go out of their way to eat it. (It can be very hard to establish these in an xeriscaped yard for this reason; the deer mow the plants down as soon as they're planted).

According to Bureau of Land Management botanist Roger Rosentreter, sagebrush is like the “meat and potatoes” of a mule deer’s diet in winter. Just as with human diets, a variety of foods helps deer stay healthier. Bitterbrush and other shrubs provide different nutrients to help the deer make it through winter.

“A mule deer diet of sagebrush and a little bit of bitterbrush is high quality winter forage,” says Rosentreter. “The deer prefer the bitterbrush but they will do very well if you have both. They compliment each other with proteins and nutrients. It also aids in deer digestion to have both.”

Protecting and restoring native plants ensures that deer can bulk up. This in turn makes it easier to survive heavy snowfall, parasites, predators and encounters with humans.--Matt Miller

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