Hunters killed 20 gray wolves in Yellowstone National Park, US, making it the bloodiest season yet.

According to reports, the illegal killings took place over a period of three months this winter. The deaths mark the most since the animals were reintroduced to the region more than two decades ago.

One pack is now considered “eliminated,” The Washington Post reports. Now, less than one hundred remain in the 3,500 square mile park, which spans across Wyoming and into Montana and Idaho.

Hunting is prohibited at Yellowstone, yet park officials fear more bouts are to come as there are months to go in Montana’s hunting season.

Wolves killed by hunters in Yellowstone National Park

Further to the story, The Washington Post reveals that the park’s superintendent is concerned about wolves being killed.

Cam Sholly reportedly said that an “extraordinary number” of Yellowstone wolves had already been killed. And, that Montana’s governor Greg Gianforte should do more to prevent it.

But Gianforte stated that any wolf entering the Montana state lines may be “harvested” under law, the news outlet adds.

Here, hunting is legal and poachers can use bait to lure animals into leghold traps.

A spokesperson for Yellowstone National Park, Morgan Warthin, told The Washington Post: “Allowances for trapping and especially baiting are a major concern, especially if these tactics lure wolves out of the park.”