RACHEL MARTIN, HOST:
In northeastern Oklahoma, there's a stretch of tallgrass prairie where bison still roam. And once a year the herd is weighed, tagged and counted to make sure it's healthy. Joe Wertz from StateImpact grabbed his microphone and headed out on Oklahoma's annual bison roundup.
JOE WERTZ: For 11 months out of the year, the 2,500 bison on the Tallgrass Prairie Preserve live the quiet life. The windswept scene looks and sounds like it did when this endangered ecosystem spanned much of the Great Plains. No traffic, no humans, just endless horizons and grass. But come November, things get busy and noisy. Metal clangs, hooves stomp and ranch hands holler.
UNIDENTIFIED MAN #1: Hey.
WERTZ: The roundup starts with the herding of hundreds of bison out of the wide-open prairie. From there, they're coaxed one by one into a narrow chute. The tall steel wall keeps the hooves and horns away from Nature Conservancy workers like Kim Elkin. She's in the middle of the line and stationed above the action on a catwalk. Elkin is the gatekeeper.
KIM ELKIN: We open and close the gates and then kind of let them through and process, so that they can go down the line and get the shots that they need to maintain their health.
WERTZ: The bison are poked and prodded in line. They respond by bucking, stomping and grunting.
ELKIN: The moms and their babies don't want to be separated, so you can hear them snorting.
BOB HAMILTON: So this is the last stop in their trip right here at the squeeze chute.
WERTZ: That's Bob Hamilton, the preserve's director. At the end of the line, the rowdy bison are vaccinated with a gun-like syringe and given a mouthful of deworming medicine. The squeeze chute also has a scale. Workers yell out the bison's weight.
UNIDENTIFIED MAN #2: Nine, two, zero.
WERTZ: Nine hundred twenty pounds - that number is recorded in a database and analyzed later in the year. To keep the herd in balance, some bison will be sold off.
UNIDENTIFIED MAN #3: Seller cow.
WERTZ: Others are keepers.
UNIDENTIFIED MAN #4: Keeper cow.
HAMILTON: All this process, running them through the corral, is ultimately to get them individually into that squeeze chute to where then we can identify them, reach in and scan their tag with the electronic wands and bring up their computer record.
WERTZ: Those computer records of weight, calf births and other observations are key to keeping the herd healthy. When European explorers landed in North America, 30 million bison roamed the continent. By the turn of the 19th century, that number had plummeted into the hundreds. Hamilton says conservation efforts like these have fueled a big bison comeback. Today, the U.S. is home to more than 160,000 bison, according to the latest report from the USDA.
HAMILTON: It's kind of the hands-on part of restoring nature. Somebody's got to do it so...
WERTZ: And he says it's a fun job. For NPR News, I'm Joe Wertz in Pawhuska, Okla.
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