Nature's Surprises - Bison Calf Born in November

“Hey, whattaya know, we got ourselves a cinnamon!” April and May are the typical calving months for our Kankakee Sand bison. So, you can imagine our utter shock and surprise when we saw a little red bison calf in the pasture this past November!

The first question that comes to mind is, “How did that happen?!” Well, we know how it happened.  The better question may be, “Why did that happen?”

Our bison breed naturally on the prairie, and rut typically happens in August and September. Rut is when the females are in estrus and are receptive to the mating with the males. Gestation for bison is approximately nine months, which puts the calves arriving right around April and May. 

This female calf was first seen on November 21, 2018. We don’t know the actual date on which she was born, because when female bison are ready to give birth, they remove themselves from the herd and find a protected area to give birth. Only when the female is ready will she bring her calf to the herd. She is kinda in charge that way.

A newborn calf’s fur is red (thus earning the nickname ‘cinnamon’), and it was this bright hue in a sea of November browns that caught our attention. Calves keep their red coats for about two and a half months. Our November calf is just now starting to turn to a chocolate brown color, and soon she will blend in with the rest of the herd.

This calf, like others born at Kankakee Sands, was born with her eyes open, could stand within minutes of being born, was able to run when she was just hours old and would have weighed 40 to 50 pounds at birth. She would have nursed solely for about a week and then would have begun to eat vegetation. She will be fully weaned from her mother’s milk within a few months and will ultimately reach her maximum weight of 800 to 1200 pounds by consuming lots and lots of prairie grasses, sedges and willows. 

But unlike the other calves at Kankakee Sands, this one was born in November. When she was approximately two and a half months old she experienced her first polar vortex, with lows of -21 F and highs of -2! I know how I felt on those days, and it wasn’t good. The little calf stayed together with the herd in the protection of the willows, with their faces to the wind, weathering the winter storm with ease. 

So, if we do that math backwards, this calf being born in late November means that mating would have happened around mid-March, which is a very atypical time for mating to happen in bison. Our theory of why this happened lies in forage quality. Bison typically mate when they are at their peak of fitness in late summer at the close of a long growing season of eating and gaining weight. Science shows that when animals have access to more forage and high-quality forage, their mating and birthing cycles can tend to swing and expand, allowing for young to be born outside the typical norm. At Kankakee Sands, the bison pastures have a myriad of short grasses, tall grasses, sedges, rushes, willows and forbs for the bison to choose from. There is an entire smorgasbord of 600 types of prairie vegetation out there to satiate each bison’s belly. Bison cows that have eaten well, put on weight and are healthy may begin to come into estrus at irregular times of the year, even at the end of winter!

So, this spring, as the prairie starts sending up its rich bounty of new green vegetation, we hope for another year of good health and good eating for our bison. More calves will certainly be born this spring, and with luck and robust cows, we may even be surprised by another cinnamon or two this fall! 

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 www.nature.org/KankakeeSands or call the office at 219-285-2184.