Beefalo or buffalo? The purebred push for bison

July was National Bison Month — but not at the Denver Zoo, which set four of the burly brown beasts free earlier this year. No, in January the zoo sent its four critters — one bull and three cows — to the Last Gulch Ranch in southeastern Colorado, where they are living with forty other bison owned by conservationist rancher Robert Alsobrook. But the zoo still owns the bison and plans to build a herd of purebred animals on the ranch so it can study how they interact with the environment compared to bison that have been interbred with cattle, says Rich Reading, conservation biology director at the zoo. Although there are more than half a million bison in the United States, only a small portion of them are genetically pure — including the four zoo animals, the two herds owned by the City of Denver, and the famous animals at Yellowstone National Park. "Bison are a keystone species," Reading says, meaning that their habits, particularly their grazing patterns, can affect living things all around them, including plants, birds and small reptiles and amphibians. And purebred bison graze differently than beefalos...more