June 22 (UPI) -- For the first time in more than 40 years, grizzly bears of Yellowstone National Park are leaving the federal government's protections list for endangered species.
U.S. Interior Secretary Ryan Zinke announced Thursday that the bears in the Greater Yellowstone Ecosystem have recovered to sufficient numbers to warrant a delisting.
"As a kid who grew up in Montana, I can tell you that this is a long time coming and very good news for many communities and advocates in the Yellowstone region," Zinke said in a statement.
The population of the Yellowstone grizzly, a localized class of the North American grizzly, has grown by about 600 in the park since it first appeared on the endangered list in 1975 -- when it numbered fewer than 150. The Interior Department said that today, it has met "all the criteria for delisting."
"This achievement stands as one of America's great conservation successes; the culmination of decades of hard work and dedication on the part of the state, tribal, federal and private partners," Zinke added. "As a Montanan, I'm proud of what we've achieved together."
Officials said multiple factors were considered in the decision to delist the bear, including scientists' belief that it has recovered to the point its population health can be sustained without the continuing aid of the federal list.
"These factors include not only the number and distribution of bears throughout the ecosystem, but also the quantity and quality of the habitat available and the states' commitments to manage the population from now on in a manner that maintains its healthy and secure status," the department said in its news release.
"They now occupy more than 22,500 square miles, an area larger than the states of New Hampshire, Massachusetts and Connecticut combined."
In addition to the removal of federal protections, the delisting will also return oversight and management of the Yellowstone grizzly to the state level -- meaning it could be shot or hunted if it leaves the boundaries of the park and local laws allow it.
However, the animal -- also known as the North American brown bear -- will continue to be covered by the endangered species list outside of the Yellowstone ecosystem, as their populations still do not meet qualifications for delisting.
Conservation and wildlife advocates have opposed removing any grizzly from the endangered species list, and some are promising to sue the government to keep the Yellowstone bear's protections intact.
"As a result of today's announcement, Yellowstone's bears may soon face a trophy hunter firing line once they roam outside the safety of our beloved national parks," WildEarth Guardians advocate Kelly Nokes and Western Environmental Law Center Director Matthew Bishop said in a joint statement Thursday. "Grizzlies in the Greater Yellowstone Ecosystem remain threatened by dwindling food sources, illegal poaching and record-high mortality rates, genetic stress from a lack of connectivity to neighboring sub-populations, and the burgeoning threats of climate change."
Established in 1872, Yellowstone National Park spans into three states -- Wyoming, Montana and Idaho -- and encompasses 2.2 million acres of land. It is home to dozens of animal populations, including some endangered and threatened species.
The final rule to delist the Yellowstone grizzly will next be published to the federal register for public review, and will take effect 30 days later, officials said.