The final showdown of Alaska's Fat Bear Week comes down to heavyweights Bear 910 and Backpack

After a week of fierce competition, Bear 910 and Backpack have emerged as the final contenders to be named the heftiest bear of Alaska's Katmai National Park and Preserve.

There can only be one winner of Fat Bear Week , and it's up to the voters to decide Tuesday.

The contest, which is in its 12th year , celebrates the resilience of the 2,200 brown bears that live in the preserve on the Alaska Peninsula, which extends from the state’s southwest corner toward the Aleutian Islands. Fat Bear Week was started in 2014 as an interactive way to inform the public about brown bears, the coastal cousins of grizzlies.

Last year’s winner, Chunk — known officially as Bear 32 — clinched his victory at an estimated 1,200 pounds. He was handily defeated in the first round of competition this year by Bucky, who went on to lose a faceoff against Backpack, known officially as Bear 89.

The event this year featured 16 bears vying for the heavyweight title in a single-elimination, bracket-style tournament. All voting is done online at www.fatbearweek.org , and a winner will be declared Tuesday evening after the final poll closes. The public can watch the bears on explore.org’s livestream cameras before deciding on their favorite.

“Fat bears are successful bears,” the nonprofit says on its website. This group gorges itself on the abundant salmon that return to the Brooks River starting in late June. It's there that they can stuff themselves to accumulate the fat reserves they'll need to survive the winter. To be featured in the contest, the bears must frequent the area around the river.

Adult male brown bears typically weigh 600 to 900 pounds (about 270 to 410 kilograms) in midsummer. By the time they are ready to hibernate after feasting on migrating and spawning salmon, large males can weigh well over 1,000 pounds (454 kilograms). Females are about one-third smaller. The bears may each eat as many as 30 fish a day this time of year, working hard to eat a year’s worth of food in about six months.

During winter hibernation, the bears do not eat or drink and lose one-third of their body weight.

Fat Bear Week's contestants also include five bear families, in recognition of the record high number of families and cubs at the river this summer. A mother must feed and protect her cubs while also eating enough calories to sustain herself through hibernation. Cubs often face the risk of attack by other bears due to territorialism or food scarcity.

Bear 132 and her three spring cubs advanced to the semifinals, but lost out to Bear 910.

Bear 132 has become one of the largest and most experienced mother bears at Brooks River, according to the nonprofit's contestant profiles. In mid-July, one of her cubs became separated from the family for several days, wandering the river corridor alone. They were reunited a few days later. ___

Jamie Stengle contributed from Dallas.