Fat Bear Week has returned, and with it comes one of the quirkiest yet most fascinating wildlife competitions on the planet. Starting September 23, 2025, the bears of Katmai National Park and Preserve in Alaska will once again compete for the unofficial title of “fattest bear,” as millions of fans across the globe cast their votes online.

But beneath the humor and memes lies a story about survival, ecosystems, and the deep connection between bears, salmon, and people. Here’s everything you need to know about Fat Bear Week 2025, from how to participate to why bulking up is a matter of life and death for these animals.

What is Fat Bear Week?

Fat Bear Week is an annual event organized by Katmai National Park, Explore.org, and the Katmai Conservancy. It works like a March Madness-style bracket, where fans vote daily for their favorite bears until a single champion is crowned.

The competition celebrates how brown bears transform over the summer. Starting lean after hibernation, they gorge on salmon, berries, and other food until they balloon into round, lumbering giants by fall.

Voting runs daily from September 23 to September 30, 2025, between noon and 9 p.m. ET. Last year, more than 1 million votes were cast, turning this once-niche event into a global sensation.

Which bears are competing this year?

This year’s contenders include a mix of veteran competitors and promising newcomers spotted along the Brooks River. Rangers hint that fans can expect to see returning favorites such as:

Bear 128, Grazer, Last year’s champion and one of Katmai’s most skilled anglers. Grazer is also notable for being the first female to win while actively raising cubs.

Bear 32, Chunk – A perennial finalist, Chunk overcame a jaw injury this year, yet still managed to pack on weight.

Alongside these stars are several fresh faces, young bears whose stories are still unfolding but who have already impressed with their size and tenacity.

Why do the bears get so fat?

The answer is survival. Brown bears at Katmai face long, harsh winters where they enter hibernation and live entirely off their fat reserves. To endure months without food, they must gain hundreds of pounds during the summer.

Right now, the bears are in a biological state called hyperphagia. Their hormones switch off the ability to feel full, allowing them to eat almost nonstop. This is especially important for females (sows):

A fertilized egg won’t implant unless the mother has enough fat reserves.

Heavier sows are more likely to survive the winter and successfully raise cubs.

Rangers note that several large, single females are in excellent condition this year, which could mean a cub boom next spring.

Why is Brooks River the perfect feeding ground?

Not all bears in Katmai bulk up equally, and Brooks River gives Fat Bear Week contestants a special advantage.

The river’s famous waterfalls, Brooks Falls, serve as a salmon buffet. Sockeye salmon gather there during spawning runs, practically lining up for the bears. This abundance allows multiple bears—often solitary animals—to fish in the same spot with relatively little conflict.

This year, the salmon run has been particularly strong, leading to unusual behavior: older adult males, or boars, have been seen playing in the water, a rare sight in the wild.

What role do salmon and Indigenous knowledge play?

The health of Katmai’s bears is inseparable from the health of its salmon. Rangers emphasize that the region hosts one of the most sustainable sockeye salmon runs in the world, thanks to centuries of stewardship by Indigenous communities.

Unlike many places where ecosystems were bent to human needs, Katmai’s ecosystems remain largely intact. This balance allows both salmon and bears to thrive together—an increasingly rare reality in modern conservation.

Who won Fat Bear Week in the past?

2023 & 2024 Champion: Grazer (Bear 128). Known for her fierceness, she made history by winning while raising cubs.

Other fan favorites: Chunk, Otis, and Holly have all made deep runs in past competitions.

Fat Bear Week’s past champions have become internet celebrities, each with their own quirks, legends, and devoted fan bases.

How can you watch Fat Bear Week 2025?

Fans don’t need to travel to Alaska to experience the spectacle. Explore.org streams live footage from Brooks Falls, where viewers can see bears fishing, splashing, and sometimes squaring off.

Live cam: Explore.org’s “Bear Cam” offers 24/7 views.

Voting: Cast ballots directly on the official Fat Bear Week website each day.

Why does Fat Bear Week matter?

While the competition is lighthearted, it serves a serious purpose: raising awareness about conservation, healthy ecosystems, and the delicate ties between wildlife and climate.

It also provides a rare chance for people to connect with nature from afar, giving millions of viewers a stake in the survival of Alaska’s brown bears.

As Katmai ranger Sarah Bruce puts it: “Bears are just the tip of the iceberg. There’s so much more to learn about this place.”

TL;DR

Fat Bear Week 2025 runs from September 23 to September 30. Fans worldwide can vote online for their favorite bears as they show off their summer gains. The competition celebrates survival, conservation, and the extraordinary bond between Katmai’s brown bears and the salmon that sustain them.