What, When Is Fat Bear Week? Watch Livestream to Help Choose National Park's Biggest Bear

Wednesday marks the first day of Fat Bear Week—a competition in which the public vote on the fattest bear in Alaska's Katmai National Park.

Each year, bears are tracked around the park by the Park Service and wildlife livestreamers Explore.org, particularly around the salmon-rich Brooks River area.

Staff then assign the bears with numbered names, like 435 Holly or 32 Chunk, so that they can more easily monitor their activity throughout the year.

Around October, the bears have had all summer to gorge on fish and get fat with winter hibernation once again around the corner. And the park makes sure to store the before-and-after photos so we can all see just how fat they've gotten.

The difference is significant. Having come out of hibernation, bears returning to the area from winter may appear thin and gaunt. But by October, some of the animals are almost unrecognizable.

The rules for Fat Bear Week are simple: Voters are presented with the late-summer photos of two bears from this year's lineup of 12 contenders. In what is essentially a knock-out tournament, they then vote on which bear they think is the fattest until only the winner remains.

But there's more to it than that. The Katmai National Park Service (NPS) has already published before-and-after photos of each of this year's bears, so while voters can simply vote on the fattest bear if they like, others might want to take into consideration which bear has gotten fattest relative to its starting weight, even if they didn't end up being the fattest overall.

And it can get even more complicated still. Through observations, the park service has published detailed biographies of each of the bears in this year's lineup, and a read-through reveals that each bear has extenuating circumstances and behavioral traits.

Bear 503, for instance, separated from his mother earlier than usual when he was young and faced what the NPS describes as "significant uncertainties" before being adopted by 435 Holly, who is also in this year's running. Despite his early life, 503 has successfully gotten fat this year, so some voters may want to take that into account.

Others may want to consider how 480 Otis is one of the older bears at Brooks River, missing two canine teeth, and needs to compete with bears who are both younger and larger than he is. He turned up later than usual to Brooks River in 2021, but by September, he'd made use of his short time and gotten fat.

That said, voters can also just vote on the fattest bear if they want. Explore.org states that Fat Bear Week is a subjective competition.

Voters can also tune into a livestream of the Brooks Falls area to observe the bears for further insight, which can be found here.

Voting opens at 9 a.m. PT on Wednesday, September 29 via the Explore.org website and closes on Tuesday, October 5, when this year's Fat Bear Week winner will be decided.

The before-and-after photos and biographies of this year's fat bears can be viewed on the Katmai National Park & Reserve website here.

Brown bear
A stock photo shows an Alaska brown bear fishing in the Brooks River. Fat Bear Week compares several large bears before hibernation. N8tureGrl/Getty