Fat Bear Week 2023 begins at Katmai National Park. Time to vote for your favorites.

One of the biggest competitions of the year is here.

After days of uncertainty over the narrowly averted government shutdown, Fat Bear Week began as scheduled Wednesday at Katmai National Park and Preserve in Alaska.

“Fat Bear Week is always a celebration of the success of the bears,” Naomi Boak, a media ranger at Katmai, told USA TODAY. “Not just the big boys, but the sows with cubs, the young teenage bears, the subadults.”

Only one, however, can be crowned Fat Bear Week champion.

Here’s what fans should know about this year’s competition and contenders.

What is Fat Bear Week at Katmai National Park and Preserve?

Fat Bear Week is a March Madness-style bracket competition that pits some of Katmai’s bulkiest and most beloved bears against each other in the arena of public opinion.

Voting began Wednesday. The bears with the most votes at the end of each day advance to the next round until a champion is crowned Oct. 10.

Over 1 million votes were cast in last year’s competition. Fans can vote for this year's contenders at explore.org/fat-bear-week.

Fat Bear Week is a partnership between Katmai National Park and Preserve, explore.org and Katmai Conservancy.

Who's competing for Fat Bear Week 2023?

The first match-up features two of the youngest bears in this year's competition: Bear 806 Jr., a first-year cub who won last week's Fat Bear Jr. competition, and Bear 428, who is described as a "pudgy 3.5-year-old subadult bear" who navigated the river independently for the first time this year.

The second poll features two mama bears: Bear 402, who has had eight least litters and boasts nearly unrivaled "maternal experience" and Bear 901, a first-time mom who was last year's Fat Bear Week runner-up.

Additional contenders can be found on Fat Bear Week's website.

Why do we celebrate Fat Bear Week?

Fat Bear Week began as Fat Bear Tuesday in 2014 and was expanded into Fat Bear Week in 2015.

It’s a celebration of the bears’ success in bulking up and the unique ecosystem that supports them.

“Without the pristine Brooks River ecosystem to support an abundant salmon run, there would be no Fat Bear champions,” according to Katmai’s press release.

Why are fat bears important?

The bears have to survive off their fat during six months of hibernation, but there are other reasons for piling on the pounds.

Boak explained the biggest, most dominant adult male bears, which are called boars, get their pick of fishing spots and mates. Meanwhile, adult female bears, or sows, need fat to raise cubs or prepare to have them the following year.

“Female bears have delayed implantation, so the eggs that have been fertilized don't implant until the bear is in hibernation and if she is fat enough,” Boak said.

What kind of bears are in Fat Bear Week?

Fat Bear Week’s bears are brown bears.

What happens after Fat Bear Week?

Fans can still watch explore.org bear cam livestreams through October. Each year, 10 million people tune in to see the bears, starting in June.

“They can follow these soap operas over many years and get to know the bears and their personalities,” Boak said. “I mean there are some people on the bear cams who can identify the bears far better than we rangers can because they have eight cameras they’re watching and we can only be in one place at a time.”

She said the bears begin going into hibernation at the end of October and re-emerge in March or April.

What is the controversy with Fat Bear Week?

Last year, spam bots cast thousands of fraudulent votes, but Katmai National Park and Preserve said it easily deciphered which ones were fake and tossed them out.

“We don’t want any scandals,” Boak said. “Just enjoy it with your friends.”

Who won Fat Bear Week 2022?

Bear 747 won Fat Bear Weeks 2022 and 2020.

You can see all the previous winners in explore.org’s Fat Bear Week Hall of Champions.

Is Otis the bear still alive?

Not only is Bear 480 Otis alive, but he's in the running for Fat Bear Week 2023.

He won the very first Fat Bear challenge, Fat Bear Tuesday, in 2014 and went on to win Fat Bear Weeks 2016, 2017 and 2021.

Rangers weren’t sure he’d be back this year because he’d already lived to his late 20s, past the expected age of most brown bears. But he returned in late July.

“He was terribly, terribly skinny, but he's not skinny anymore,” Boak said with a smile. “I mean, his philosophy is eat more, move less. And he is one of the most successful anglers on the river. He will just sit there, and he will catch fish. And the contrast between the beginning of the season and now is just incredible … He’s amazing.”

What about other fan favorites?

“Pay attention to the usual suspects because their body sizes may be different,” Boak said, sharing these updates.

Bear 151 Walker: “He started out as a very kind of shy, smaller bear, and he has grown really big. So now he’s throwing his weight around, testing to see where he can be in the hierarchy on the Brooks River, and sometimes it works, sometimes it doesn't, for him.”

Bear 128 Grazer: “Even though she's a female, (she) is one of the dominant bears on the river, and she's probably the best angler we have. She's huge, just huge.”

Bear 435 Holly: 2019’s Fat Bear Week winner “again is huge.” Boak noted neither 435 Holly nor 128 Grazer had cubs this year, so they’ve been able to easily fatten up without spending extra energy on cubs.

Bear 901: Last year’s runner-up had three cubs this year and lost one. “But she looks terrific. She's not as fat as she was last year, of course, but we have to cheer her on.”

Bear 910's cub and niece: Last season, Bear 909 and Bear 910, who are sisters, raised their cubs together, which Boak said, "We've never seen before. It's highly unusual.” Equally unusual, Boak said when it was time for Bear 909 to “boot out her cub” this year, the cub wasn’t quite ready and was adopted by her aunt, Bear 910, who raised her along with her own cub. Both Bear 910's cub and adopted niece are competing this year.

Teachers can help students learn more about bears with Fat Bear Week in the Classroom.

“I just love it when we hear from kids and from teachers. They get so enthusiastic about the bears,” Boak said. “It's a great way to get connected to nature and understanding about bears in the wild.”

This article originally appeared on USA TODAY: Fat Bear Week begins at Katmai National Park: Meet the contenders