Correction : 9/19/2013 This story was updated to remove that the men pleaded guilty to Hunting After Legal Hours. They were arrested on suspicion of that, but it was not part of the plea deal.
Joseph Nevling, James Cole, George Plummer, and Michael Courtney, all from the Pee Dee area of South Carolina, were caught using poison arrows to hunt near Collbran in Colorado on September 7, Mike Porras with Colorado Parks and Wildlife in Grand Junction, Colorado said.
Porras says a concerned hunter called in a tip to Operation Game Thief back in 2012.
"Our officers contacted two of these individuals last year at their hunt camp and the following year, this hunting season, the investigators were looking for them and they returned to the area and during the surveillance, we observed them committing these crimes," said Porras.
Plummer and Nevling, both of Timmonsville, Courtney, of Florence, and Cole, of Sumter, all pleaded guilty on Tuesday to Illegal taking of Wildlife and Illegal Use of Toxins in Hunting.
"They will also be facing a hearing for a Colorado Parks and Wildlife hearing commissioner that will further determine whether they'll be able to hunt in Colorado and 38 other wildlife violator compact states. One of those states includes South Carolina," said Porras.
Authorities say Plummer used poison arrows to hunt deer, elk and bears. Authorities say Plummer told them he'd been using the illegal equipment in Colorado for at least 20 years.
Porras said one of the men admitted to using the poison as a form of insurance .
"They were guaranteeing themselves a kill by the use of a toxicant and certainly that's not what we consider to be ethical and fair hunting and doesn't fall into the tenants of what we call fair chase," Porras said.
The four men did have licenses to hunt in Colorado.
All four were ordered to pay several thousands of dollars in fines and court costs.
The men also agreed not to hunt in Colorado over the next four years, Porras added.
According to the South Carolina Department of Natural Resources, using poisonous archery equipment is illegal on public lands and is illegal to possess because it's a federally controlled substance.
The Associated Press contributed to this report.