Bison calves make history at Broken Kettle

And there could be one or two more this year.

"That would be the last I would expect," said Scott Moats, preserve manager, last week.

These calves, born in The Nature Conservancy's Broken Kettle Grasslands Preserve, are the first to be born in Iowa in more than 150 years.

"They look healthy. They are moving well with the herd," Moats said. "They are playing."

The 28-member herd freely roams the 500-acre pasture inside the preserve in the Loess Hills in western Plymouth County, which means getting a peek at the new arrivals is hit and miss.

Some days the herd can be seen from 234th Street and other times the animals are out of sight depending on where they are grazing in the pasture.

The calves born and those expected fall into line with Moats' estimate that 75 percent of the 12 mature cows were bred. Two of the cows are still nursing late calves from last year.

"Bison on their own don't necessarily breed every year," Moats said. "So if they already have a calf they probably won't breed because it will be too much stress on her system."

Many of the bison cows will wean their calves at about 8 months of age because the cows will be pregnant and it will mean too much stress on their bodies, Moats said.

However it is up to the individual cow, he added.

"We still have our calf from last year still nursing on the cow. He's almost two-thirds the size of the cow," Moats said. "That's where the individual cow's decision to cut them loose comes in."

He expects the bison will start breeding in mid-July for next year's calf crop.

Each year's calves are important as they help move forward the conservancy's plan to build a 250-adult bison herd.

Moats said the pasture condition looks good right now and he expects the herd will be in good shape throughout the summer and coming into the winter.

"There's plenty of grass out there," Moats said. "I would anticipate having plenty of forage to support them throughout the winter."