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Guest post by Alyssa Nyberg of Kankakee Sands

Just like many of us that are working from home, our bison continue to work from their home at Kankakee Sands. The bison have been busy enriching the plant diversity by eating a plethora of grasses, creating sandy depressions when they wallow in the ground, and pooping out nutrients to enrich the soil, just as they have been doing since they arrived in 2016 when they were brought to Kankakee Sands to assist us in managing our prairies.

And this spring, about 25 of our 70 bison will take on an additional job—parenting.

These 25-female bison–called cows–are at least three years old and would have mated last fall with one of the several mature bull bison at Kankakee Sands. Bison and humans have a similar gestation period of nine months, so we are in the prime of calving season this May.

When it comes to calves, there is a term called weaning rate. It is the percentage of mature females that give birth to a calf in a year. Our weaning rate over the past several years has been between approximately 90%, which means nine out of every ten mature bison cows gave birth.

If we maintain that weaning rate this year, our herd could grow by 22 little calves! However, bison cows typically only give birth two out of every three years. Perhaps this will be the year that our rates drop to the weaning rate that we are seeing at other TNC herds around the country, closer to 60%. If that were to be the case, then we would see approximately 14 calves born at Kankakee Sands this year.

Though we are a little iffy on the number of calves that will be born, we know that when the cows are ready to give birth, they will move away from the herd, often into an area of thick vegetation where they will be safe and secluded. After birthing, when the female is ready, she and her calf will return to the herd and will stay together in that group for protection, just as they do in the wild.

The calves are born with reddish colored fur and weigh forty to fifty pounds. Due to the reddish hues of their fur, bison calves are often referred to as “red dogs.” As they get older, their fur will darken to shades of brown, and they will ultimately reach 800 to 1200 pounds if they are a female, and 1700 to 2000 pounds if they are male.

Bison calves are born with their eyes open, can stand within minutes of being born, and can run when they are just hours old. These are handy traits for a calf to have when historically it would have been born onto a prairie with such predators as wolves.

Just like all mammals, bison calves nurse. When they are as young as a week old, they begin eating vegetation. Calves are fully weaned from their mother’s milk within a few months.

For those bison that are going to be first-time mothers, this will be a very different spring. And for all of us humans experiencing the COVID-19 pandemic, this is indeed a very different spring.

The Bison Viewing Area is currently closed at this time, but rest assured that our bison will continue to remain hard at work on the prairies at Kankakee Sands, will be raising the next generation of Kankakee Sands bison, and will be ready to be admired when the stay at home orders are lifted.

Stay safe, everyone.


The Nature Conservancy’s Kankakee Sands is an 8,400-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. Photo credit © Jason Whalen/Big Foot Media