Grizzly bears are emerging from their dens roughly a month ahead of schedule, according to Yellowstone park officials who say the spring-like weather is to blame.

The first confirmed report of grizzly activity was on Feb. 9, when a bear was spotted scavenging on a bison carcass.

After months of hibernation, grizzlies are ravenous and typically feed on the carcasses of winter-killed animals like bison, deer and elk.

Park staff even conduct annual surveys to locate such carcasses and designate certain areas of the 2.2-million acre park off-limits to prevent human-bear interaction.

However, this year's survey is incomplete so it's too early to know what the warmer temperatures could mean for the bears' top food source.

"It is certainly possible that a milder winter could have an impact on the number of animals that succumb to the winter cold, and it certainly could have an impact on that food source availability as the grizzlies wake up," Al Nash, a spokesman for the park, told

Park officials are warning visitors to avoid carcasses, carry bear spray, hike in groups and make noise to avoid startling grizzlies, which can react aggressively if interrupted while feeding.

The effects of climate change

Early rising could be part of the new normal for Yellowstone's estimated 600 grizzlies. The past decade has been the hottest on average for the park, and climate models indicate that Yellowstone's temperature will continue to rise over the next century.

"We're getting 40-degree days in February, where we often see 20 below zero," Nash said.

Shorter winters could have a variety of impacts on the park, according to Nash. Animals like bison and elk would move into the park sooner, and predators like wolves and coyotes would follow.

According to a report by the Greater Yellowstone Coalition, milder winters would likely mean that fewer grizzly cubs would survive due to the lack of food sources.

Climate change has already had an impact on Yellowstone's whitebark pines, with higher temperatures enabling bark beetles to destroy more than 95 percent of the region's trees since 2009.

Whitebark pines are a keystone species, and grizzlies and other species depend heavily on the seeds for their diet.

Related on MNN: