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Welcome toFat Bear Weekat Mashable! Each fall,Watch Internal Affairs Online Katmai National Park holds a competition as Alaska’s brown bears finish fattening up for their long winter hibernation. This year, Mashable is getting in on the salmon-munching action. Check back with us all week as we follow the fat bear face-offs each day, and remember to get your votes in for each round. Happy fishing!

Fat bear aficionados, it's time to meet your final four.

In an upset that won't soon be forgotten, Bear 32 Chunk took down the most dominant bear at the river this summer, Bear 856. Bear 856's fat just couldn't cut it.

In Saturday's second matchup, Bear 747 -- a beloved fat bear by watchers of the river's drama -- also advanced to the final four beating out the smaller, Bear 719.

The week's mayhem has been leading to this first matchup of the final four between two big beauties of the Brooks River: Divot and Beadnose.

Divot is most known for the time she was rescued by Katmai National Park rangers after she was caught in a snare some years ago. You can still see the mark left by that snare in the form of a scar around her neck.

Beadnose is now a full-fledged internet celebrity after a photo of her sitting on the river bank in all her fat glory was shared on Twitter alongside an image of her more svelte self from earlier in the summer.

"Fat is a sign of a successful bear and these bears need enough to survive up to six months of hibernation," Katmai wrote on its Facebook page opening up the voting.

"In this round: metabolic magician 409 Beadnose goes up against no stranger to the gallery of calories, 854 Divot. Whose salmon-sourced cellulite supersedes?"

You can vote for whichever bear you think has fattened up the most on Katmai's Facebook page by hitting the "Like" button on the bear you think is most deserving of the first spot in the final. Voting will remain open until 10:00 p.m. ET on Sunday.

Beadnose or Divot will then go on to face either Bear 747 or Chunk, depending on the results of their match on Monday.

While Fat Bear Week is fun and games for everyone watching, it's literally a matter of life and death for the bears themselves.

Brown bears fatten up during Alaska's summer months in order to make it through hibernation during the long, dark, and cold winters.

The fattest bears have the best chance of living off those fat stores -- built of calorie dense salmon -- and emerging relatively unscathed as the seasons change again.