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Bison are a big draw for visitors to Yellowstone National Park. And the park wants to grow its herd by about 15%. But that's a problem for Yellowstone's neighbor, the state of Montana, which is threatening to sue. Here's Olivia Weitz of Wyoming Public Radio.
OLIVIA WEITZ, BYLINE: Stopped along a trail just past some of Yellowstone National Park's bubbling mud pots, Maren Powell and her 4-year-old son, Makai, say they came here hoping to see bison.
MAREN POWELL: This is our first trip. It's the second trip for the grandparents, though.
MAKAI: The babies don't have the biggest horns. Their horns are only, like, a little big.
WEITZ: The newborn calves and their mothers, lazily sunbathing on warm sand nearby, are some of the last remaining wild bison in America. The park helped save them from extinction more than a century ago. The park is now home to about 5,200 bison. A new management plan allows for up to 6,000 animals. But the state of Montana wants to cut the herd size in half, threatening a lawsuit to protect cattle ranchers if it grows. Raylee Honeycutt, with the ranching industry group Montana Stockgrowers Association, says park bison are a threat to their livelihood because in the winter, bison often look for food on public and private land outside the park.
RAYLEE HONEYCUTT: The increase in the bison population increases the likelihood of bison migration to go out of the park, which increases the likelihood of brucellosis transmission.
WEITZ: Brucellosis is a reproductive disease some Yellowstone bison carry, which can also infect cattle. If it's found in a single Montana cow, entire herds could be quarantined there, devastating its beef industry.
HONEYCUTT: Obviously, we're disappointed in the decision in the move to increase the bison herd.
WEITZ: Back in 1995, Montana sued over ranchers' concerns. A court-mediated settlement to reduce the population each year has been in place since then. Yellowstone Park superintendent Cam Sholly says he doesn't get why the state would sue now.
CAM SHOLLY: I don't understand the logic. We haven't had a brucellosis transmission between bison and cattle.
WEITZ: While there hasn't been a confirmed transmission from bison to cattle, a study shows elk have infected cattle dozens of times since 1998, and cattle ranchers aren't demanding elk be restricted to the park. Only bison are mostly constrained to park boundaries. A previous Montana governor created tolerance zones where bison are allowed, adjacent to the park. Sholly says they work.
SHOLLY: The question is why? Why would you change the tolerance zones? That's the question for the state.
WEITZ: Yellowstone does kill some bison infected with brucellosis. And in recent years, it's reduced its herd size by shipping more than 400 animals to Native American tribes, which are eager to get them.
JASON BALDES: My vision is thousands of buffalo on tens to hundreds of thousands of acres.
WEITZ: Jason Baldes' Eastern Shoshone Tribe has received 15 bison from the park to help build its herd in Wyoming. The Shoshone and others hope to get more in the future.
BALDES: The number of population in Yellowstone is directly related to the number of animals that we can restore to tribes.
WEITZ: For now, Montana's threat to sue to reduce Yellowstone bison numbers is just that. And the park's plan to grow its herd is still just a plan. What happens will likely depend on which party wins the White House and control the National Park Service come November.
For NPR News, I'm Olivia Weitz in Cody, Wyo.
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