BADLANDS NATIONAL PARK, S.D. — The Big Pig Dig is just about dug.

The fossil field formally known as the Pig Wallow Site at Badlands National Park will close for good at the end of this summer, 15 years after student paleontologists started unearthing prehistoric remains.

"The main research of the site is to better understand how fossils are preserved and how bones accumulate in a particular setting. And the site is very unique here at the Badlands. We've never found a site like it in the White River Badlands," said Rachel Benton, park paleontologist.

Excavation started in June 1993 after two visitors found a large backbone sticking out of the ground near the Conata Picnic Area in what researchers think was a watering hole that trapped animals in mud.

Since then, 5,000 to 10,000 visitors have stopped by every summer to see National Park Service staff and students from the South Dakota School of Mines & Technology in Rapid City remove sediment that covers the fossils.

Work at the Pig Dig happens under a shelter just off the Badlands Loop Scenic Byway, so it's easy to watch.

The Badlands park doesn't have any dinosaur bones, but the area is rich in fossils of other creatures.

The dig name stems from the first fossil that was initially thought to be the remains of an ancient pig-like mammal called Archaeotherium. Though fossils of that creature have been found at the site, researchers later determined the initial bone was from a hornless rhinoceros called a Subhyracodon.

Eighteen other species have been found at the dig, including ancient three-toed horses, tiny deer-like creatures, turtles and a bobcat-sized saber-tooth cat. More than 10,000 bones have been excavated from the site for research purposes, Benton said.

After this summer, the focus will shift to comparing the findings to other fossil accumulations, she said.

Since the 1993 discovery of the Pig Dig, technology has helped park staff find other sites reported by visitors, said Matt Weiler, a former School of Mines student who worked on the site and now is a paleontology technician with the National Park Service.

Badlands National Park is free range, which means visitors can go anywhere inside the boundaries.

Because more people use GPS units, they're able to provide park staff with more accurate locations of fossils they find, he said.

"You can just plug it right into ours and navigate to the spot. It makes it easier for us and for the visitor because they've got the specific coordinates" and don't have to rely on remembering landmarks, Weiler said. "We're having a much higher success rate finding the stuff they reported."

Park staffers stress with visitors the importance of leaving alone anything they find and just reporting the location to a park ranger or the visitor center so the site remains undisturbed.

Stealing fossils brings a large fine.

"There is no collecting allowed in the park without a signed research permit from the superintendent," Benton said.

The combination of student research and visitor education has worked well at The Big Pig Dig, so the park staff hopes to get funding to do the same thing at one of the other potential sites on the park in the future, Benton said.