Get fat or die.

In the unforgiving Alaskan wilderness, amassing hundreds of pounds over a few months is a necessity. Fat Bear Week — the annual celebration of the success of Alaska's rotund brown bears hosted by Katmai National Park and Preserve — has returned. The bears must outlast the long high latitude winter without eating. And while hibernating, mothers must nurse cubs in their dens, too.

One of the most popular wildlife livestreams on Earth, the explore.org bear cams, beamed back footage of the bears feasting on salmon this summer. Now, you, the voting public, can choose the fattest of the fat bears in a playoff-like single elimination tournament. Don't worry, all the bears are winners. But the contest is an engaging way to recognize the triumph of these hardy omnivores in the protected Katmai wilds.

The park has released the 2023 Fat Bear Week bracket, which you can see below. Voting starts on Oct. 4, and you can look at a comparison of each match-up before clicking on your choice (details below). Some of the bears have returned to Katmai's Brooks River, a waterway teeming with salmon, for around two decades.

SEE ALSO: Park rangers saw something unprecedented in this year's fat bears

In recent years, the watershed that supports Katmai, Alaska's Bristol Bay, has experienced exceptional runs of salmon, including its largest ever historical run of salmon in 2022. Many of these fish swim up a primary river that feeds into Katmai. In 2023, the region's salmon runs ended up being well above average, but of great concern for the bears in Katmai, the runs were a few weeks late, including in the park's Brooks River (where the fat bears feast). Relatively gaunt bears had to wait until late July for big pulses of salmon. That's a significant seasonal change.

"It was challenging compared to recent years."

"It was challenging compared to recent years," Mike Fitz, a former Katmai park ranger and currently a resident naturalist for the wilderness livestreamers at explore.org, told Mashable. "They had to wait around."

The 2023 Fat Bear Week bracket. Credit: Katmai National Park and Preserve / Explore.org / Katmai Conservancy

That made for a trying period for animals evolved to devote much of their summer to eating copious amounts of calorie-rich foods. At Katmai, a large adult bear can eat over two dozen fish in a day. Fitz once watched the colossal bear 747 eat 15 salmon in just a few hours. Ultimately, some bears left the Brooks River for better fishing grounds, but would later return in September.

What's more, higher water levels and accompanying stronger currents this summer made it challenging for younger bears and mothers with cubs to catch fish, Naomi Boak, Katmai National Park and Preserve's media ranger, told Mashable. Yet even if July was largely a bust for the bears, August didn't disappoint. "The salmon were late, but there were plenty of salmon in the river," Boak said.

Many of the competitors in this year's Fat Bear Week are well-known veterans of Katmai's rivers. They've succeeded each year, growing large and well-equipped for their Alaskan hibernation. For example:

- Bear 747: Bear 747 is the largest bear many Katmai park rangers have ever seen. He's a former Fat Bear Week champion. "He seems to be more hippopotamus than bear at times," a ranger once told Mashable.

- Bear 128, "Grazer": Grazer is an especially fierce bear who vigilantly protects her young. She's one of the river's most dominant bears. "Grazer is a particularly defensive mother bear," explore.org explains. "She often preemptively confronts and attacks much larger bears — even large and dominant adult males — in order to ensure her cubs are safe."

- Bear 480, "Otis": Otis, a multiple Fat Bear Week victor, may be the most famous bear on Earth. He's often conspicuous on the livestreamed bear cams, patiently waiting to catch passing salmon. In 2021, he was the champion we all needed. He's now a three-time winner.

The park has posted before-after-after-images of bears, which you can find on Katmai's site. Their transformations, like bear 32 "Chunk" shown below, are impressive:

The 2023 transformation of bear 32, "Chunk." Credit: NPS / K. Moore / F. Jimenez

How to vote in Fat Bear Week

Voting in Fat Bear Week is easy:

• Voting opens on Oct. 4 and runs through the Fat Bear Week finals, on Oct. 10.

• On the day of each vote, visit the explore.org website: https://explore.org/fat-bear-week

• Then, "select your choice by clicking or tapping on your preferred bear photo," the organization explains. "Then enter your email where prompted. Select ‘I am not a robot’ then submit. You know that you have successfully voted if you see the total votes for each bear."

Happy voting. And happy Fat Bear Week.