By Laura Zuckerman
SALMON, Idaho (Reuters) - Montana authorities are examining the remains of a bison from Yellowstone National Park found dead from suspicious circumstances on Thursday after at least two other buffalo were illegally shot to death in the area.
The killings come just over a week after the state and federal agencies that oversee the nation's last pure-bred herd of wild buffalo struck a deal to allow the animals to roam into some parts of Montana without facing capture or slaughter.
The buffalo, or bison, have for decades been barred from making their historic winter migration into Montana when food is scarce in the park's snow-covered high country.
Ranchers are outraged by the free-roaming plan because some Yellowstone bison carry brucellosis, a bacterial infection that can cause pregnant cows to spontaneously abort. Wildlife advocates have hailed the agreement for ushering in a new era of tolerance for the famed herd.
In recent days, tensions over the agreement have escalated in Gardiner, the Montana town near Yellowstone's north entrance, where some have taken exception to the roaming bison.
Last Friday, state game wardens were called to the area to investigate a mass shooting of a group of bison bulls that ultimately left two of the animals dead.
Some of the animals were struck by dozens of gunshots from a small-caliber firearm not intended for large game.
On Thursday, the investigation took a new twist when the carcass of another bison was uncovered by officers for Montana's wildlife agency in what wardens said appears to be unrelated to the shootings last Friday.
Sam Sheppard, state warden captain, said the killings are all but unprecedented, adding: "This is not something we want to see happen."
It is unlawful to shoot Yellowstone bison in the park and illegal to shoot them in Montana outside of a licensed hunt.
Findings from the probe of the first incident were expected to be delivered next week to a local prosecutor, who ultimately must decide if poaching or other charges will be brought.
Wildlife advocates said the crimes underscore the need to protect Yellowstone's bison.
"These animals were shot numerous times with a small gun, which prolonged their pain and terror," said Buffalo Field Campaign head Dan Brister.
Roughly 700 of the 3,700 Yellowstone bison herd have been captured and corralled this winter for migrating into Montana.
A legal furor that erupted over plans to slaughter those bison that tested positive for brucellosis ended when Montana Governor Brian Schweitzer in February granting the captured animals a stay of execution.
(Editing by Dan Whitcomb and Steve Gorman)