Brown bears like Beadnose gain hundreds of pounds each autumn to prepare for their winter sleep. Check out the next photo in the gallery to see what she looked like a few months earlier!
Brown bears like Beadnose gain hundreds of pounds each autumn to prepare for their winter sleep. Check out the next photo in the gallery to see what she looked like a few months earlier!
Photograph by NPS Photo / A. Ramos

Fat Bear Week

Get the inside scoop on how these brown bears pack on the pounds to prepare for winter, and see before-and-after pictures of fat bears!

A brown bear named Walker stands patiently on a rock at the top of Brooks Falls in Alaska’s Katmai National Park and Preserve in July. He and about 10 other bears are waiting for sockeye salmon to leap up and over the six-foot-high rocky falls on their way to breeding grounds upstream—and hopefully right into their hungry mouths.

As a fish shoots out of the water, the thousand-pound bear snatches it in his jaws—score! Just below the falls in Brooks River, a bear named 747 stands neck-deep in the choppy waters called the jacuzzi. He face-plants into the frothy river, snapping up a swimmer with ease.

The bears don’t know it, but in summer and fall, they’re being watched … and cheered. As if they’re at a pie-eating contest, people want these bears to gorge on salmon till it looks like their bellies will burst. And during Fat Bear Week, the humans cast their ballots for the biggest, best bear.

On-camera snacking

To survive the coming winter, brown bears must pack on the pounds so they can sleep up to seven months while food is scarce. When they begin their feeding frenzy—usually in July—adult males weigh between 600 and 900 pounds. 

By the time Fat Bear Week rolls around in late September or early October, some brown bears are topping over a thousand pounds. (Adult females weigh about a third less than males.)

Rangers set up cameras around the park to monitor the bears and show people how important the Katmai ecosystem is. In summer and fall, thousands of people tune in to watch the fish-catching.

Then during Fat Bear Week, viewers vote for their favorite burly bear. Soon after, the carnivores will waddle off to sleep for about half a year.

“For these bears, fatness means success,” says Amber Kraft, interpretation and education program manager at Katmai National Park. “Fat Bear Week celebrates that success and the health of their ecosystem.”

Big bears win

Fat Bear Week might sound silly, but it’s all about survival. As the weather turns cold, usually in late October or November, brown bears enter their dens for a period of light hibernation to wait out the winter when food is scarce. To conserve energy, the bear’s body temperature drops by 10 degrees, they breathe just once or twice a minute, and their heart beats just 12 times a minute, says Jennifer Fortin-Noreus, a bear biologist with the U.S. Fish and Wildlife Service. (Deep hibernators enter a rest so intense that it’s almost impossible to revive them. But brown bears often shift positions, and they can easily wake up to react to danger or give birth.)

The bears also won’t eat, drink, or even go to the bathroom during this time. That’s why they have to constantly chow down in the months before their light hibernation so they can survive off the fat stored in their bodies.

“Fat bears are ready for the winter,” Kraft says. “And this is serious business—if a pregnant female doesn’t have enough fat, her cubs won’t survive.”

Fishy feast

Good thing these bears could win any eating contest you entered them in! In late summer and fall, they forage up to 14 hours a day, feasting on grass, berries, rodents, and—of course—nutrient-packed salmon. In June and July, bears catch the salmon as they swim upriver in Katmai to lay their eggs. By September, the fish start to die off. So the bears catch these easy meals as the salmon float back downstream.

“One sockeye salmon in early summer contains about 4,500 calories—that’s about nine cheeseburgers’ worth of energy,” says Mike Fitz, a former National Park Service ranger who created Fat Bear Week. And a bear might eat 40 salmon in a day. This phase of nonstop eating is called hyperphagia (pronounced hi-PER-fay-zhuh), and scientists think that the bears can keep eating because their brains and bodies prevent them from feeling full during this time (compared to how you would feel after eating 360 cheeseburgers).

Luckily, Katmai National Park is like an all-day buffet. Every June, almost a million sockeye salmon leave the Pacific Ocean and swim up the rivers. Because the park has such a healthy number of salmon, more than 2,200 bears can call the park home.

Meet some contestants

Fat Bear Week gets started after rangers select 12 contenders. The bears are chosen based on things like having before-and-after pictures of the skinny spring bear and the fat fall bear, and if the animal has wandered onto the livestream at Brooks Falls that year. (That would increase the chances that people can see the animal during Fat Bear Week.) They also try to choose both males and females of different ages.

When it’s time to vote, it’s not just about which bear packed on the most pounds. Sometimes people root for a mother bear raising her cubs or an older underdog bear with chipped teeth. And it’s also about the journey to jumbo-size.

“Fat Bear Week isn’t just about body size,” Fitz says. “It’s about the different ways bears get fat."

See before-and-after pictures of a few Fat Bear Week winners! 

25-year-old Otis emerged a bit late from hibernation last year in June 2021.
25-year-old Otis emerged a bit late from hibernation last year in June 2021.
Photograph courtesy of N. Boak

Let the voting begin

We’ll have to wait until October to find out which bear won in 2022. But the winner won’t have too long to celebrate: A few weeks after the polls closed, all the bears of Katmai waddled into their hillside dens. Over the next few months, each bear lost up to one-third of its body weight—up to 466 pounds—while they snoozed through the snowy season.

In April, the bears emerged from their dens and went back to normal brown bear life—they usually forage in the morning and evening, then rest during the day. Then this summer, the bears got back to business.

No matter which bear takes home the trophy in 2022, these roly-poly critters are all winners. “It’s like a sporting event,” Kraft says. “Everyone has their favorite bear.”