Some guest grazers are gracing Zollman Zoo.

Three bison cows from Minneopa State Park in Mankato arrived in November as part of a program to increase the population of the animals in the state.

This year, Zollman Zoo joined the Minnesota Bison Conservation Herd. The Olmsted County zoo, in Byron, is the fourth organization to join the herd, which has about 130 head of bison throughout the state.

Zollman Zoo has had bison since the mid-1980s. However, the zoo had to wait for recent genetic test results to join Blue Mounds State Park Luverne, Minneopa State Park and the Minnesota Zoo in Apple Valley as part of the statewide herd initiative.

While only up to five or six of those bison will ever live at Zollman Zoo at any given time, the zoo’s role in conserving and growing the state’s bison population will still help create genetic diversity within the conservation herd.

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Two female bison from Zollman were moved to the Minnesota Zoo to breed with bison there. One resident cow and the three females on loan to Zollman will have a chance to breed with the zoo’s resident bull.

“Having four here at the park doesn’t seem like it would be a lot,” said Jaide Ryks, Zollman Zoo naturalist. “If you think of it like your family tree, you’re going to get a lot of offspring — four different family lines — from those four bison alone.”

The genetic testing of the Zollman bison found no indications that the bison had cross-bred with cattle. That makes them good candidates to help grow the state conservation herd. Genetic tests also show the state conservation herd doesn’t have traces of cattle DNA, according to the Minnesota Department of Natural Resources.

The long-term goal, set by the DNR and the Minnesota Zoological Garden, is to grow the state herd to 500 bison so that the population here can be sustained.

The DNR and the Minnesota Zoological Garden are coordinating the conservation herd partnership.

An estimated 50 million American plains bison used to roam the Upper Midwest before hunting dwindled their numbers down to fewer than 1,000. Ryks said she's excited to be part of an effort to thoughtfully increase the number of bison.

“We’re not just a zoo that keeps animals in cages,” she said.

Most of the zoo animals are rehabilitated animals that wouldn’t survive in the wild, she added. Once at the zoo, animals there usually play a role in conservation and education efforts.

The female bison are adjusting to their new temporary surroundings, Ryks said.

Initially used to grazing as their sole source of food and wary of zoo staff, they’ve adjusted to their supplemental feed.

As for their other task, bison don’t breed until late summer or early autumn. However, they don’t seem to mind the bull’s company.

“They like to hang out with him,” Ryks said.

That’s a good start.

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John Molseed is a tree-hugging Minnesota transplant making his way through his state parks passport. This column is a space for stories of people doing their part (and more) to keep Minnesota green. Send questions, comments and suggestions to life@postbulletin.com.