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.

When bear 856 shows up, other bears notice.

Sometimes they flee.

For nearly a decade, bear 856 has been the most dominant bear of Katmai National Park and Preserve's Brooks River — home to the fat bears. Dominance means bear 856 sits atop the bear hierarchy. His intimidating, aggressive behavior earns him the best fishing spots, and for bears attempting to fatten up for the long, harsh, Alaskan hibernation, 4,500-calorie salmon are everything.

Bear 856 is so dominant that he rarely needs to fight. His presence alone regularly intimidates other bears. When 856 shows up at the river, he often displaces bears, meaning they move off to another fishing spot, or leave the river altogether. If other bears fish nearby 856, it's because he tolerates their presence. Sometimes bear 856 will chase other dominant bears from the river, as seen in 2018 bear cam footage.

There are certainly often other large, menacing bears around. But none have yet to successfully challenge 856. He's been the king of the river, almost continually, since 2011.

"856 remained at the top of the hierarchy this year," said Mike Fitz, the resident naturalist for explore.org and a former park ranger at Katmai. "I was wondering if he would be challenged. It hasn’t happened yet."

"856 is still the big boss," agreed Naomi Boak, the media ranger at Katmai National Park and Preserve.

Like you, bears don't like to unnecessarily subject themselves to the possibility of severe injury. This summer, Fitz didn't spot bear 856 doing any fighting, just intimidating, by facing down or approaching other bears. "Other bears know his reputation and respect him," noted Fitz.

But if necessary, bear 856 will violently dominate other large, powerful bears (as seen in the 2018 clip below).

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Bear 856, however, isn't the fattest or largest bear of the Brooks River. That title goes to the formidable bear 747, who is likely the fattest bear this year. Bear 856 is certainly large, but what he might sometimes lack in size, he makes up for in assertiveness and attitude.

"He has ‘tude like no other bear on the river," said Boak. "It's an impressive run," she said, referencing his consistent dominance since 2011.

Bear 856's lapse in dominance came in 2017. That year, he appeared at the Brooks River with a limp, indicating a leg injury. He lost his assertiveness. He didn't displace other bears from the river. But the next year, bear 856 returned in good health. He proceeded to approach other large, dominant males, scuffle, and displace them.

He's been the dominant bear ever since, even as he ages. Bear 856 is around 20 years old, which is about the life expectancy of Katmai's bears. But he's clearly an exceptionally successful bear, and like Lebron James, may have an impressively sustained run of late-career dominance.

It's unlikely bear 856 will ever win a Fat Bear Week contest. Other bears naturally just appear pudgier come fall, whereas 856 is a bit taller than many bears and doesn't grow as rotund. What's more, bear 856 also devotes considerable time over the summer to pursuing females, explained Fitz. He's not quite as devoted to fishing as the spectacularly fat bear 747 and the legendary Otis, two of the more popular, and plumper, bears.

Bear 856 lost in the first round of Fat Bear Week this year, to the round-bottomed bear 151. But his true legacy continues.

"He's been the most consistently dominant bear at the river since 2011," marveled Fitz. "It's been remarkable to see him remain successful."