For Fermilab’s bison farm, a surprise times five

One of the five newborn bison calves stays close to its mother. Photo: Joseph Piergrossi

Four weeks ago, Cleo Garcia, Fermilab’s resident bison herdsman, noticed a few bison cows had unusually full udders. Within the span of the past two weeks, those cows have given Fermilab five new calves.

The new arrivals come as a big surprise. In 2010, Garcia and the farm’s veterinarians believed the timing of the cows’ breeding cycles would not allow them to reproduce. In early October last fall, Garcia separated three young bulls from the herd, and the farm sold off the oldest one.

“Evidently, before that, the youngest bull decided to leave its mark,” Garcia said.

The farm controls when the bulls interact with the cows to avoid calves being born during winter or summer, when temperatures are too extreme. In April, the farm received two new bulls from a ranch in Wisconsin in hopes of breeding calves for next year, thinking this year there would be no new offspring. Then came this month’s surprises.

The first calf was born on May 30, with another three arriving between June 5 and 6 and the most recent on June 9. All of the calves – and their mothers – are in good health. A sixth calf may be on the way.

After the birth of the fourth calf, Garcia drove his truck into the field of tall grass, where the bison were calmly eating and rolling in the dusty dirt. The new mothers backed away, protecting their brood.

“Who knows, we might have another beyond the sixth one,” Garcia said, pointing to another cow that was starting to show signs she was expecting. “I think it’s wonderful. It’s always good when the herd can grow.”

Joseph Piergrossi