A crossbreeding experiment that became a “breed” is the bison-cattle composite called the Beefalo.

HAYDEN VALLEY — Perhaps no other occurrence in Yellowstone National Park has the potential to transport visitors back in time quite like the bison breeding season.

“Those cows continued to produce calves well into their late teens. But it took several generations — breeding them down to about 1/16 bison — to get fertility in the males.

Hormonal attraction is key during mating season, which is why bulls roll around in urine-soaked mud. To a bison cow, that smells like the finest cologne. The bison rut from August to September.

Though people controlled much of the hybridization between bison and cattle, some was likely accidental, or the result of cattle escaping to the wild and breeding. Generally, though the vast ...

A farmyard cow in Poland has chosen freedom this winter, roaming with a herd of bison for three months after escaping its pen.

Mating could also contaminate the endangered bison population's gene pool. In 1927, no European bison remained in the wild, and 54 remained in captivity.

Kowalczyk and others are planning to interrupt this narrative come summer to prevent the cow from mating with a bison. If the cow can be located and approached in the warmer months, she will be ...