(Reuters) - Grizzly bears at Yellowstone National Park are emerging from winter hibernation weeks earlier than normal because of the arrival of spring-like weather, with warmer-than-usual temperatures and rain instead of snow, a park spokesman said on Tuesday.

Yellowstone on Monday confirmed the first report of a grizzly roaming the central part of the park, where it was seen scavenging on a bison carcass, according to spokesman Al Nash.

Nash said the emergence of grizzlies comes roughly a month earlier than in recent years, with the first sightings of the bears from 2012 to 2014 happening between March 4 and March 14.

Grizzlies are ravenous after periods of hibernation that can span months and in which eating and other activities are suspended, Nash said. The outsized, hump-shouldered bruins typically feed on the carcasses of winter-killed animals like bison, elk and deer for the quick intake of needed calories, he said.

The 2.2-million-acre (890,000-hectare) park that spans parts of Wyoming, Montana and Idaho is warning visitors to be on the lookout for the bears since they are not usually active during February, a month at the park that sees many fewer visitors than at the height of tourist season in the summer, Nash said.

“It’s important to make sure visitors during this period are aware that they already need to be thinking about proper actions in bear country,” he said.

That includes avoiding carcasses if seen, carrying bear spray, hiking in groups of at least three people and making noise to avoid startling bears and causing them to act defensively.

Grizzly bears in the lower 48 states were listed as threatened under the U.S. Endangered Species Act in 1975 after hunting, trapping and poisoning reduced their numbers to roughly 1,000 from about 100,000.

The Yellowstone area contains an estimated 600 grizzlies, or the bulk of such bears that still roam the lower 48 states.

A government panel that oversees Yellowstone-area grizzlies has said the population has recovered and should be stripped of federal protections, opening the way for hunting.