Bison herds at Minnesota parks expected to add 35 calves this spring

As of late May, about 10 bison calves have joined the 30-member herd at Minneopa State Park. (Minnesota Department of Natural Resources / Supplied)

Around 35 calves are expected to be added to bison herds at Minnesota parks this birthing season, the Minnesota Department of Natural Resources estimates.

In a news release on Tuesday, the DNR reported 10 bison calves have already been born to a 30-member herd at Minneopa State Park, just west of Mankato. At Blue Mounds State Park in southwest Minnesota near Sioux Falls, the herd there has grown by about 20 calves.

Officials say it's "impossible" to estimate new births based on appearance because the cow's body doesn't change significantly during pregnancy.

"So far, the new calves appear to be healthy and well-adjusted," said Minneopa State Park supervisor Ashley Steevens. "Each day we monitor the herd and note any new additions. So far, the birth rate is typical."

The DNR adds: "Newborn bison calves are reddish brown in color, weigh 30 to 50 pounds, and stand upright almost immediately after birth. Female bison move away from the herd when they give birth and keep the calf away from the herd for a few days. Full-grown bison bulls weigh up to 2,000 pounds and can stand at six feet in height. Adult cows weigh an average of 800 pounds and stand four to five feet tall."

DNR provides prairie bus tours for people who want to get a look at the bison at Blue Mounds.

At Minneopa, "bison drives" are open each day of the week except Wednesday. Visitors can tune their car radios to 1610AM for information.