Welcome toFat Bear Week 2020! Katmai National Park and Preserve’s brown bears spent the summer gorging on 4,500-calorie salmon, and they've transformed into rotund giants, some over 1,000 pounds. The park is holding its annual playoff-like competition for the fattest of the fat bears (you can vote onlinebetween Sept. 30 and Oct. 6). Mashable will be following all the ursine activity.

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He is colossal.

Bear 747 — a bear who really grew into a usually mundane number assigned by Park Service biologists — is often the biggest bear at Katmai National Park and Preserve's Brooks River, home to the livestreaming bear cams. In recent years, bear experts say he's weighed well over 1,000 pounds. He's never, however, won the Fat Bear Week contest.

But has 747 been the fattest?It's fair to say 747 has been just as fat, if not fatter, than the fat bear champs over the last four or so years. But Fat Bear Week, a lighthearted celebration of these thriving wild animals, is a subjective competition. The public votes, and ultimately other impressively fat bears have finished first.

In 2020, the votes will fall as they may. But there's a truly immense bear romping around Katmai National Park and Preserve, all the fatter after an immense 2020 salmon run. 747 is the biggest, and almost certainly the fattest bear this year.

"If Fat Bear Week were based on size alone, it would likely be no contest," said Mike Fitz, a former Katmai park ranger and currently a resident naturalist for explore.org. "747 appears to be at least as massive as last year when he was estimated to weigh more than 1,400 pounds, and I would not be surprised if he is even heavier this year."

"He's the fattest and largest bear I've ever seen," added Fitz, who has spent years professionally observing bears. "I feel a special bit of privilege to witness a bear as big as he."

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Bear 747, like all the bears at Katmai's Brooks River this year, benefited from a record-breaking run of salmon swimming up a major river that feeds into Katmai. "In July, it was just phenomenal to see how many salmon were coming up the river,"said Naomi Boak, the media ranger at Katmai National Park and Preserve. At some points, she said, so many fish crowded the river beneath the Brooks River waterfall that some salmon were pushed out of the river, onto the banks.

Rangers spotted 747 devouring fish nearly every day in July. It paid off.

"There's no dispute he’s the biggest bear at the river," said Boak, who noted she's not endorsing any bear.

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Bear 747 fishing the Brooks River in Sept. 2020.Credit: nps

What's more, bear 747 benefited from excellent efficiency this year. He didn't need to expel much energy to catch fish. Salmon were everywhere. 747 merely showed up. "Once the salmon arrived he spent a lot of time at the falls without having to expend much effort to secure his meals," explained Fitz.

The greater story, beyond the profoundly fat bears this year, is what happens when a natural ecosystem is allowed to thrive. Katmai is a protected land, and the state of Alaska ensures the salmon entering this region aren't overfished. "This is a story about a very healthy ecosystem," said Boak. (Alaska stands in sharp contrast to once thriving, but now collapsed fisheries, like the Atlantic cod. "It's all about the salmon at Brooks," Boak added.

"He's the fattest and largest bear I've ever seen."

Katmai is part of the Bristol Bay watershed, home to the largest run of sockeye salmon on Earth. While flourishing today, the Trump administration has restarted a process to potentially allow a giant, unprecedented, copper and gold mineto open in the watershed. Ecologists emphasize that such a mining district would have unacceptably adverse impacts to the fishery. The thriving salmon run exists, in large part, because salmon have unimpeded, unpolluted access to all the region's rivers and streams, where the fish breed and develop.

The fat bears are a testament to the success of this natural system. Everyone's fat this year, no matter who wins. All these bears are well-endowed to survive the long, harsh, Alaskan hibernation.

"Each bear in the 'competition' has found success in its own way," said Fitz.