Massive mammal built to withstand freezing temperatures
By Rose Neville, Ouabache Naturalist
There are many reasons why the North American bison is our country’s national mammal. They are very impressive animals with unique adaptations that allow them to survive heat and the extreme cold.
Their thick woolly coat allows them to withstand temperatures as low as -40 degrees. It consists of coarse guard hairs that provide adequate insulation. This thick coat insulates so well that snow can start to accumulate on the fur. This means that the bison keeps most of the heat. If not, the heat would escape and would melt the snow.
Their skin will also thicken, and fat will be deposited just below the skin that will act as insulation as well. This is especially useful during blizzards with strong winds as the bison faces into the blizzard head on. They will face into storms with 50 mph wind, hunker down and wait until the harsh storm passes.
Their iconic humps are key to surviving harsh winters. The humps consist of huge muscles that are intertwined with their vertebrates. These strong muscles allow the bison to control their massive heads. Their head alone can weigh more than 70 pounds.
When there are thick blankets of snow on the ground, they will use their heads as a snowplow. With the snow out of the way, they can forage for winter grasses. This also creates essentially a highway through the snow that then other animals may use to move around. This is important in the Great Plains area as pronghorns are not well adapted to the snow.
These winter grasses don’t contain nearly as many nutrients as the summer grasses, so bison have come up with some clever ways to work around this. During cold stress, bison can slow down their metabolism. This allows them to require less nutrients as they minimize the amount of food being converted to energy. The winter grasses also are harder to digest so it stays in their stomachs longer. Body heat is generated through digestion, and, since digestion takes longer, more heat is generated this way.
Through their thick coats and slower metabolism, the bison feel nice and toasty despite the cold temperatures.
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