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Welcome toFat Bear Week 2019! Katmai National Park's 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 Oct. 2 and Oct. 8), and Mashable will be following the ursine activity. 

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Bear 503 should have been dead.

The now seven-year-old young adult male bear, who grew fat enough this summer for Katmai National Park rangers to include him in the 2019 Fat Bear Week competition, found himself in dire straits in the summer of 2014. As a cub, he clung to a tree and wailed into Alaska's tranquil, boundless air. He was helpless, motherless, and abandoned.

Unable to catch fish by himself, park biologists almost certainly expected him to starve to death, or worse.

But then, the unexpected happened.

Bear 503 was adopted. And he was adopted by Bear 435, "Holly," who, interestingly, might very well be the fattest of all the fat bears this year.

"I watched 503 when he was a newly emancipated yearling in 2014," said Mike Fitz, a former park ranger at Katmai National Park and currently a resident naturalist for explore.org. "He looked small and vulnerable in those weeks before he was adopted by Holly. Looking at him now, it's like I'm watching a different bear."

Bear 503 in September 2019.Credit: NPS Photo / B.Lutes

As a year-and-a-half old cub, it's not clear why 503's mother, Bear 402, abandoned him. But there's a compelling hypothesis: She was forced to.

You see, the river's most dominant male began to follow Bear 402, as she had gone into estrus. It's dangerous for cubs to hang around big, aggressive males, so Bear 503 likely embarked on his own when the courtship began, explained Fitz.

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But 503 was quickly in dire straits. After spending a day howling in a spruce tree near the famous explore.org bear cams, he wandered the shores of a lake alone. He was skinny and directionless.

But a couple of days later, 503 appeared at the river with Holly and her biological cub. And he wasn't just tagging along.

SEE ALSO:This is the fattest bear

"He was treated like one of her biological offspring. He nursed alongside Holly’s spring cub," noted Fitz. "He was given the same care and guidance as her spring cub. He was a full member of the family."

Documentation of such bear "adoptions" are profoundly rare, and Holly's rationale will remain unknown. Her adoption could have been inspired by something we humans might interpret as altruism — if such a thing truly exists. Or it could have had a more pragmatic justification, like three bodies in a winter den is warmer than just two.

But what is certain is that, five years after 503's abandonment, the bear with long legs and dark rings around his eyes has matured into a healthy, successful animal.

"I’m eager to follow 503’s story as he grows into a fully grown adult," said Fitz. "He is quite tall, especially for a bear that isn't quite seven years old, and he's become very skilled at fishing the most productive fishing spots at Brooks Falls."

In 2014, Bear 503 wandered alone in Katmai National Park.Credit: nps

503's Fat Bear Week match-up is Saturday, Oct. 5. With older, larger, and significantly fatter bears in the bracket, it's exceedingly unlikely that he'll be a victor, or even close to a victor, in this year's competition.

Though, of course, he's already a victor, having survived what amounts to a life-threatening abandonment at an early age.

Perhaps he'll be a great force to reckon with in the coming years. He's an increasingly formidable young adult in a world teeming with fish. He's survived numerous, harsh winter hibernations alone. He's proven.

In a few year's time, 503 might not just be a success story. Maybe he'll vie to be king of the river.

TopicsAnimals

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