Shedding that Winter Coat

By Alyssa Nyberg, Restoration Ecologist at The Nature Conservancy’s Kankakee Sands

Just this past week, I just put away all my winter clothes and brought out my summer clothes. Turns out bison are doing the same thing!

Our Kankakee Sands bison herd spent the winter on the prairie, with their insulating fur coats keeping them comfortable during the coldest of days. Now that the prairie is warming up, the bison are shedding their thick coats of winter fur.

Bison fur does not fall out like my dog’s fur – one piece here, a few pieces there. Rather, bison’s fur falls off in clumps and bunches, giving them a raggedy patchy appearance. To facilitate the sloughing of the fur, bison often rub on trees, willows, stumps and even wallow on the ground.

Photo by Olivia Schouten, TNC

Our Kankakee Sands staff has been finding clumps of bison fur stuck on bushes, nestled in dense grass, even wedged in fencing. Some fur is dark brown, others light brown, some is straight and silky, others curly and matted. Fascinating!

The calves born this spring have on their auburn spring coats. The calves (also known as ‘red dogs’ and ‘cinnamons’) will be shedding their red hues for darker ones when they are three to five months old.

Be it dark brown or light, straight or curly, bison fur is very valuable to the other inhabitants of the prairie. Birds use the strands of fur to weave together their nests. Birds and small mammals alike use the fur to insulate their nests. Fur and hair are some of the best natural insulators, especially when it gets wet. And on the prairie in spring, things do get wet!

If you’ve ever been wearing wool clothing and gotten wet, you’ll know what I mean. You can be quite warm on a rainy day in a wool sweater or wool socks.

A 2009 study at the Tallgrass Prairie Preserve in Oklahoma suggests that the insulating capacity of bison fur assists in the survival of small grassland birds whose nests are exposed to more wind and precipitation due to their distance from the ground. The researchers found bison fur in more than 40% of the birds’ nests that they encountered. The majority of the nests that had bison fur were smaller nests built by birds in plants above the ground.

Photo by Olivia Schouten, TNC

Some of the bird species that have been documented to utilize bison fur in their nests are field sparrow, Bell’s vireo, lark sparrow, common yellowthroat and American goldfinch. So, the next time you are see or hear one of these species at Kankakee Sands, you might wonder if they have included bison fur in their nests.

Should you come across a bird or small mammal nest while hiking, carefully peer inside and look for the brown squiggles of fur from our nation’s largest land mammal. Bison are known to be a keystone species – a species that defines an entire ecosystem. At Kankakee Sands, we are only beginning to explore the many ways that bison define the prairies here – from eating the vegetation, creating wallows, pooing out nutrients, and sloughing off fur. There’s so much yet to discover– come visit and learn along with us!

Remember that Kankakee Sands is free and open to the public every day of the year. Come on out this summer! And please join us on September 24th for our Kankakee Sands 25th Anniversary Celebration, and also on November 5th to celebrate National Bison Day. To find out more, visit


The Nature Conservancy’s Kankakee Sands is an 8,300-acre prairie and savanna habitat in Northwest Indiana, open every day of the year for public enjoyment.  For more information about Kankakee Sands, visit or call the office at 219-285-2184.

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