At any given time, hundreds of people are tuned into the brown bear livefeeds streaming from Explore.org, which show the most famous residents of Alaska’s Katmai National Park and Reserve in their natural habitat. Viewers may see bears playing with each other or eating salmon at Brooks Falls, but many come to the site to check one thing in particular: How fat the bears have gotten since their last viewing session.

The obsession over the brown bears’ bulk is the basis of Fat Bear Week, an annual online event organized by Katmai National Park. “Working on the webcam—and even prior to that, just being a ranger at Katmai and talking to people when they were watching the bears—I knew that bears were very charismatic creatures,” Mike Fitz, resident naturalist for Explore.org and the founder of Fat Bear Week, tells Mental Floss. “I knew that people are very curious about [the bears'] lives and how they make a living, and the point of Fat Bear Week is to make some of those stories more accessible to people and do it in a fun way.”

What originally began in 2014 as a one-day event (Fat Bear Tuesday) has since grown into a much-anticipated international event. About 55,000 voters participated in Fat Bear Week 2018. In 2019, that number grew to 250,000, and in 2020 it ballooned to 650,000. Already, 2021's event—which takes place from September 29 through October 5, 2021—promises to be even chunkier thanks to one gigantic bruin ready to defend his Fat Bear title and a fun, new (and totally adorable) twist.

A Substantial Idea

Bear 128, a.k.a. Grazer—a Fat Bear Week fan favorite.Katmai National Park and Reserve via Flickr

For people who would rather watch wildlife webcams than sports, Fat Bear Week is basically March Madness. For one week in late September and early October, Katmai posts brackets of the park’s biggest bears on the internet. Members of the public pick which bear they think is fattest (whether they judge that by literal size, the amount of weight gained since spring, or how well the bear flaunts its flab is up to them), and the corpulent contestants with the most votes move ahead in the competition. At the end of the week, the bear that wins the final match-up is named that year’s fattest.

“It’s celebrating something we normally don’t get to celebrate, which is fatness, and fatness as something good and positive, because the bears survive on their fat,” Katmai National Park’s media ranger Naomi Boak tells Mental Floss.

Mike Fitz found the inspiration for Fat Bear Tuesday while browsing livestream comments during his days as a ranger for Katmai National Park. “Somebody in the comments watching the webcam had a picture of a bear in July and also in September, and they were like, ‘wow, look at the difference!’”

He shared the comment with his colleagues, and together they brainstormed ways to turn the fun observation into an opportunity for public engagement. They came up with a smaller, one-day version of the fat bear competition, and when they posted their first-ever brackets on the Katmai Facebook page, the response was encouraging. Though the park didn’t have the largest social media presence at the time, their existing followers were enthusiastic about the campaign.

"Otis, he's enormous! I'm a little afraid that he might explode," one commenter said of that year's winner leading up to the event.

"What a difference a little (a lot) of salmon can make!" another follower wrote when the bracket went live.

Fat Bear Tuesday was a success.

“It was a great way to communicate the different ways that bears get fat and why they get fat and what that means for their survival, so we decided to expand it into a whole week to give more a people an opportunity to participate,” Fitz says. Katmai kicked off its first official Fat Bear Week the following year, and its reach has grown exponentially in the years since.

“I kind of had an idea based on my interactions with the public in the past that people would enjoy it, but I had no idea that it would grow as large as it is today," Fitz says. "It really has exceeded expectations.”

Behind the Brackets

Bears gathering to eat salmon at Brooks Falls in Katmai National Park and Reserve.Katmai National Park and Reserve via Flickr

The event is no longer the casual social media engagement experiment it was seven years ago. To get the brackets ready for late September, Boak begins planning months in advance. “I start as soon as I get [to the park] in May taking pictures of skinny bears,” she says. “Because in Fat Bear Week, we juxtapose a skinny picture with the fattest picture we can get at the end of the season, so people can see really what a great accomplishment it is for the bears to get fat to survive six months of famine.”

Though Fat Bear Week is a digital campaign, much of the work required to put it together takes place in the field. To get her pictures, Boak spends weeks skulking around areas where the bears are known to frequent, such as Brooks Falls. A good photograph can boost a contestant’s chances of winning, and snapping the perfect shot is often easier said than done. The best time to take a bear’s “after” picture is in September, when they’re close to achieving their hibernation bod, but this is also when they spend most of their time in the water gorging on salmon. This makes it hard to capture their full silhouette in all its glory on camera—though it’s not impossible.

“We essentially stalk bears for a couple of weeks,” Boak says. “With 747, our winner last year, I literally stalked him for two weeks to get good enough light that wasn’t in the fog and to see him out of the water. I had to go to the falls at different hours, I had to look around the park." In the meantime, visitors are taking their own amateur bear photographs. To widen the pool of pictures they have to choose from, the park turns to its guests, and many are willing to share their shots for Fat Bear Week.

Learning to recognize the bears is a skill in itself. After watching them for months—or years, in many cases—Boak and her colleagues start to recognize the physical and behavioral characteristics that make them unique. (Behavior becomes especially important as the bears begin their pre-hibernation transformations.) Katmai also has bear monitors whose job it is to watch individual specimens for hours at a time and note their identifiable traits, including energy levels, sleep habits, and relationships to other bears.

All that hard work pays off come autumn. Fat Bear Week is one of Katmai National Park’s most-anticipated annual events, and it’s one of the best examples of how national parks can use technology to raise awareness of what goes on within their borders. Katmai is one of the few places on Earth where the ecosystem is functioning at its full potential. The park saw a record-breaking salmon run last year, and the life-giving fat the brown bears gained as a result is a wonder of nature. By highlighting such a pristine environment, the people involved with Fat Bear Week hope to remind the public what’s at stake as environmental threats worsen.

“The phenomenon we enjoy at Brooks Falls of bears fishing there is completely dependent on a healthy salmon run, and with climate change and other threats to salmon, like large-scale development and mining, I think the more people that are aware of this healthy, productive ecosystem, the better,” Fitz says.

The conservation message underlies the campaign, but above all, Fat Bear Week is a chance for the people putting it together and the fans voting from home to have fun. “I think it’s a great relief, a happy time, and a happy, fun event to stop thinking about fires, hurricanes, and pandemics,” Boak says.

Stiff Competition

Cub of bear 435 ahead of the 2020 hibernation season.Katmai National Park and Reserve via Flickr

Fat Bear Week 2021 will be a little different from years past. For the second year in a row, the contest will be held on Explore.org to open it up to participants without a Facebook account. And for the first time ever, voters will be able to choose their favorite chubby bear cubs in addition to the mature fat bears.

Fat Bear Jr. takes place from September 23 to September 24, and the winning cub of that competition will get to go head-to-head with the big guys and ladies when the official Fat Bear Week kicks off on September 29. After a week of voting, the winner of Fat Bear Week 2021 will be determined on October 5.

Katmai’s bears are still in the process of bulking up for winter, but fans who have been watching the bears all year already know which contenders to keep an eye on. “I’m looking forward to seeing whether or not 747 can defend his title,” Fitz says. “He’s a giant bear, he’s the largest bear I've ever seen. Last year he was about 1400 pounds, so I’d be surprised if he’s any smaller this year.”

Boak agrees that 747 is the bear to beat: “I think the current champ is highly competitive. His belly is already touching the ground.” But part of the fun of Fat Bear Week is its unpredictability. Until the final votes are cast in October, no one—not even the experts who follow the bears in the park—knows who will claim the title.

“Sometimes there are really tense moments for us, where we're thinking this bear is going to win, then all of a sudden a dark horse—or a dark bear—appears as the fan favorite,” Boak says. “It’s going to be very competitive, so who knows—because the public decides, not us.”