For the first time in 150 years, bison have been born on native prairie in Iowa within a herd established exclusively for conservation.

Bison help native grasslands to thrive. But most bison herds today aren’t pure — they’ve been bred with cattle. Only two herds exist in the United States that show no evidence of cattle genes. These herds are serving as “source” herds for efforts to reintroduce pure bison to other prairie locations, such as Iowa’s Broken Kettle Grasslands Preserve.

Which explains why the birth of several calves has generated so much excitement. Twenty-eight “pure” bison were introduced to Broken Kettle in October 2008. If the herd can continue to grow, it will help with large-scale prairie restoration efforts in the state.

Nature.org spoke with Scott Moats, director of stewardship at Broken Kettle, to find out more about the bison reintroductions and what it means for the prairie.

Nature.org: Congratulations on the first bison calves born at Broken Kettle Grasslands Preserve! What does this tell you about the condition of the prairie and the herd?

Scott Moats: It tells me that our prairie is healthy and diverse enough to support our bison herd, to meet their demands in terms of forage abundance, availability and quality.

We moved them from South Dakota last year and we had a pretty tough winter here in Iowa. That they’re able to calve tells me the forage is adequate and everything they need is here. They should be able to thrive and do what we want them to do ecologically.

Nature.org: Since the prairie is providing sustainable habitat for the herd, do you expect more calves to be born this year?

Scott Moats: We expect up to 9 calves to be born at Broken Kettle this year.

Nature.org: Is it rare for bison to successfully reproduce in the wild?

Scott Moats: It is not rare for bison to successfully reproduce in the wild. If it were a rare occurrence, we would have never amassed the herds that historically roamed the grasslands.

But these are the first bison born on native prairie in Iowa in more than a century and a half, at least within a herd established strictly for conservation. It’s no coincidence this occurred at Broken Kettle — this preserve represents the largest contiguous native prairie in Iowa.

Nature.org: The bison at Broken Kettle are considered genetically valuable. What does that mean?

Scott Moats: This herd shows no signs of cattle introgression, which makes it valuable in terms of genetic conservation of the species. There are only two known herds that show no signs of cattle genes — those herds are at Wind Cave National Park and Yellowstone.

Nature.org: Why is The Nature Conservancy in the business of managing bison herds anyway?

Scott Moats: The Nature Conservancy utilizes bison as a management tool to produce a “disturbance” on the landscape that helps create a healthier and more diverse prairie. Now that we’ve returned this rare population of bison to Iowa’s premier prairie, we expect native grasses and wildflowers will do even better. And species like prairie rattlesnake, grassland birds and insects will benefit, too.

Nature.org: What’s next? Will more bison be reintroduced, or do you have enough to recreate a viable population?

Scott Moats: More bison will be introduced to the Broken Kettle herd in the next few years to help increase the population. We eventually want to maintain a herd of 200 animals.

(May 2009)

Photo credits (top to bottom, left to right): Eric Robley/TNC (bison calf at Broken Kettle Grasslands Preserve); Photo courtesy of Scott Moats; Elizabeth Niven/TNC (bison arrive at Broken Kettle Grasslands Preserve); Eric Robley/TNC (bison calf at Broken Kettle Grasslands Preserve)