This Fat Bear Week mom adopted and raised an abandoned cub

Welcome to Fat Bear Week at Mashable! Each fall, Katmai National Park holds a competition as Alaska’s brown bears finish fattening up for their long winter hibernation. This year, Mashable is getting in on the salmon-munching action. Check back with us all week as we follow the fat bear face-offs each day, and remember to get your votes in for each round. Happy fishing!

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In July 2014, a stranded bear cub spent the night clinging to the upper reaches of a spruce tree along the banks of the Brooks River in Katmai National Park, Alaska. 

After spending at least 24 hours curled up amid the branches, the young, largely helpless bear likely succumbed to thirst and hunger, and crawled down.

The 1.5 year-old bear was motherless and alone. Rangers in Katmai watched as a dominant male had begun to pursue and soon mate with the cub’s mother, Bear 402, forcing the female bear to either abandon the cub or push it out on its own earlier than expected.

Hungry and distraught, the cub wandered the pumice-covered shores of frigid Naknek Lake. Things appeared dire for the little bear, who was ill-equipped to catch fish on its own. 

The stranded bear cub.

But by the end of July, something surprising happened. 

The cub was seen trailing Bear 435, Holly, a popular bear cam bear and competitor in this year’s Fat Bear Week contest to pick the fattest bear at the Brooks River. 

As the summer advanced, it appeared Holly (who already had her own biological cub in tow) had “adopted” this stranded bear, which rangers soon gave the identifying number “503.”

Four years later, Bear 503 is a successful young adult bear. So successful, in fact, that he too is squaring off in the Fat Bear Week bracket. 

But without the aid of Holly, it’s unlikely he would have survived. Around two out of three brown bear cubs die even under good circumstances. 

“He was a full member of the family”

“Looking back, I understand now how rare of an opportunity it was to witness Holly, her biological cub, and 503 together,” Mike Fitz, a former Katmai ranger who documented the adoption event, said over email. 

“We saw that 503 wasn’t just tolerated by Holly,” said Fitz. “He was treated like one of her biological offspring. He nursed alongside Holly’s spring cub. He was given the same care and guidance as her spring cub. He was a full member of the family.”

Holly and her cubs at the mouth of the Brooks River.

The family group, now three, was spotted everywhere together, as they napped, nursed, and fed. As summer waned, they also grew fat together. Eventually, they hibernated together. 

Such a wild adoption event appears to be quite rare, but it’s not altogether unprecedented. After digging through the bear research literature, Fitz found scientists had mentioned it occurring before, but the researchers didn’t document the rich details of such an adoption. 

“The research didn’t describe how mothers cared for adopted cubs or how the cubs interacted with their new siblings,” said Fitz.

It will always be uncertain exactly why Holly adopted 503. 

As Fitz speculated that summer, it could have been altruism, or something approximating altruism. But maybe that’s just what, we — the human viewers — wanted it to be. 

Bear 435

And even if pure altruism does exist in the animal world, the adoption might have actually been a strategic survival technique: The Alaskan winter is long, relentless, and harsh.

“Will an extra warm body in the den benefit her and her genetic cub during hibernation?” Fitz wondered.

Abandoned, or set free?

The somewhat forgotten story, overshadowed by the adoption, is why Bear 402 — 503’s biological mother — abandoned him.

The most sensible reason is that, after being pursued by a massive male bear that wanted to mate with 402, she was forced to abandon 503.

But, 503 might not actually have been abandoned. 

In 2014, Holly’s spring cub on left, with bear 503 on the right.

“I no longer think that is an accurate description of what happened,” said Fitz. “He was emancipated.”

In Fitz’s view, Bear 402 did not ditch her young offspring. Instead, she “freed” 503 a bit earlier than is typical. 

Bear 402, rangers soon observed, had entered estrus and was physiologically prepared to mate again. A large male, Bear 856, took notice.

Normally, a mother bear will defend her cubs from approaching males, as they’ve been known to threaten and kill cubs.

A beefed-up Bear 503 in September 2017.

But in July 2014, Bear 402 began to let the large, intimidating male approach. Eventually, said Fitz, this was likely the cub’s signal to get going — on his own.

He did, and landed in a new family group captained and protected by Holly. From all appearances, that adoption served 503 tremendous benefit. He’s now a Fat Bear Week competitor, after all.

“503 is growing fast and he’s already quite large for his age,” said Fitz. 

“More than any other brown bear story at Brooks River, his demonstrates perseverance against the odds and (so far) success in a tough landscape.”