Winter on the Prairie
Late fall brings cold temperatures and occasional snows to the prairie, but the harshest part of the year is reserved for winter. Precipitation, in the form of snow, on the prairies usually falls sideways because the wind is driving it. But winter is not a time for major precipitation in the plains. Bone-chilling temperatures, sometimes dropping as low as -40°F, combined with winds of up to 70 miles per hour means that survival for wildlife is just as much about body heat as finding food.
Pronghorn band up in large herds and seek out areas that are more protected from the wind although their pelage (coat) is well-adapted to cold conditions. Inside each of the coarse hairs on a pronghorn is a pocket of air; collectively these hollow hairs help the animal conserve body heat. While pronghorn are not “migratory” in the same sense as waterfowl or songbirds they will sometimes journey several hundred miles or more in the winter months.
Another strategy animals use to keep warm in the winter months is to simply go below ground. The burrow system of a prairie dog can be as warm as 55°F in the winter months, providing a stable and relatively warm climate for prairie dogs. Black-tailed prairie dogs, the most common and widespread of the five prairie dog species, typically do not hibernate. In the winter months they live off of their body fat and will also forage for roots. If the climate is extreme, like that found in the Canadian prairies in winter, then prairie dogs can and will hibernate. Dry conditions can force prairie dogs into hibernation, which recently happened in Kansas during a particularly dry fall and winter. In that case the prairie dogs were unable to build up sufficient fat reserves to make it through the winter.
One of the heartiest animals on the prairie is the bison. They use their large and powerful heads to brush away deep snows to reach the good grass buried beneath. Socially, they are split into two groups: the bachelor band, consisting of mature bulls and the matriarchal band, containing the rest of the herd. Bison are quite active in winter and consistently keep moving despite the weather. Other animals, such as deer, will bed down during a snowstorm to conserve heat.
For a black-footed ferret, winter is a time of territoriality. In late November the hormones of male black-footed ferrets begin to change, and throughout the winter months those hormones build towards breeding. It is common for males to patrol their territory and mark on small shrubs or prairie dog burrow mounds. This behavior, known as scent marking, is accomplished through urination, anal gland deposit, rubbing sebaceous belly glands on an object or some combination of the three. All are signposts and warnings to other males.
The long and thin body shape of a black-footed ferret is relatively inefficient for conserving body heat. They cannot curl up into a ball and sleep in the snow like a fox, however the secret to body heat for a black-footed ferret lies in their metabolism and their habitat. First, black-footed ferrets rarely stand still when aboveground in winter. They are always moving and that constant movement, fueled by a high metabolism, creates a lot of body heat; so much body heat that the ambient temperature is really of no concern to a black-footed ferret as long as it is moving. Snow does not seem to bother black-footed ferrets much either. As they bound across a snow-covered prairie dog colony, black-footed ferrets leave a distinctive twin-print track. But a black-footed ferret cannot keep moving 24 hours a day and has to sleep. This is where their habitat, prairie dog burrows, is a key component in maintaining body heat. That relatively warm burrow system, lined with grasses and other bedding materials, provides an excellent microclimate for a sleeping black-footed ferret.
For most prairie animals winter is the harshest time of the year, but many adaptations make survival easier. If unable to move to a warmer climate, like migrating birds, then animals must find ways to endure frigid temperatures, howling winds and occasional deep snow drifts. Those that survive make it to spring, a time of breeding and renewal for many prairie species.