DENVER (CBS4)– The wild west returned to Colorado on Tuesday when wildlife officers conducted a bison roundup on the Rocky Mountain Arsenal National Wildlife Refuge. The roundup is to ensure the animals are healthy.

It was the fourth year for the roundup where the herd of bison is pushed into a corral where U.S. Fish & Wildlife Service agents can gather data.

(credit: CBS)

(credit: CBS)

One of the most important elements of the roundup is implanting a chip in the yearlings where data is collected. The chip has a number associated with it and that number corresponds to medical records.

PHOTO GALLERY: Rocky Mountain Arsenal National Wildlife Refuge Bison Roundup

The checkups aren’t the hard part but the roundup can get tricky because bison are large and aggressive.

Bison rounded up at the Rocky Mountain Arsenal (credit: CBS)

Bison rounded up at the Rocky Mountain Arsenal (credit: CBS)

Two pickups force the bison onto a path that leads into the corral. Once the bison are ushered into the corral the medical work begins. Hair and blood samples are taken, weight is measured and some of the bison are chipped.

“It’s something that is very unique to Denver, it’s a great opportunity to be able to drive five minutes outside of downtown Denver and see a bison herd like this, it’s pretty spectacular with the mountains in the background,” said  Rocky Mountain Wildlife Refuge Assistant Manger Nick Kaczor. “We’re pretty proud of this herd and we hope the public comes out and enjoys it as well.”

The bison roundup at the Rocky Mountain Arsenal (credit: CBS)

The bison roundup at the Rocky Mountain Arsenal (credit: CBS)

The Rocky Mountain Arsenal National Wildlife Refuge is located at 6550 Gateway Road in Commerce City and spens nearly 17,000 acres, making it one of the largest urban wildlife refuges in the United States. It consists of open lakes, wetlands, prairie grasslands, and woodlands.

(credit: CBS)

(credit: CBS)