A mama fat bear mauled another bear. Here's why.

The livestreamed fat bear cams are delightful. But they also reveal a harsh, competitive bear world.

On July 19, when many bears gathered at the Brooks River in Alaska's Katmai National Park and Preserve to catch big sockeye salmon at a popular ursine fishing spot, a well-known mother bear attacked another, younger bear. The scene, while not bloody, is intense and lurid, so it comes with a graphic warning.

As shown in the YouTube video below, recorded from the explore.org livestream of Katmai's bears (of Fat Bear Week internet fame), a younger bear attempts to steal a fish from bear 128, aka "Grazer." Grazer reacts by using her jaws to violently grab and attack the bear. The event underscores the brutal competitiveness of the bear world.

"This situation highlights the risk and competition that bears experience in order to satisfy their hunger and defend their cubs," Mike Fitz, a former park ranger at Katmai and now a resident naturalist for explore.org, explains in the 14-minute video.

Here's a brief rundown:

Starting at 1:35: The young "teenage" bear, who's around 2.5 years old, successfully steals a fish from Grazer and her two cubs, who are standing atop the waterfall on the left. It's an impressive accomplishment, because Grazer is a particularly defensive, alert bear. "Being able to steal a fish from Grazer is no small feat," noted Fitz.

Starting at 3:05: The small bear, emboldened by its previous success, again approaches the bear family.

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Starting at 3:52 [Graphic warning]:The small bear tries to grab another fish from Grazer, but Grazer clinches the top of the bear's neck and head in her jaws. She holds the bear for some 30 seconds, at times violently twisting and shaking the bear's head.

"For a lack of a better word, she's mauling it," observed Fitz.

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Eventually, Grazer lets go and the young bear retreats. The defeated bear has clearly just been dominated and potentially injured by a larger, older, and more established bear.

But for the younger bear, who needs to gain fat to outlast the long Alaskan winter hibernation (which is essentially an extreme fast), the risk was necessary.

"It's a tough life being a young bear," explained Fitz. "You have to face a lot of competition...to survive winter hibernation."

"It's a tough life being a young bear."

Meanwhile, Grazer also had to fend off competition for calories. She needs to fatten up for winter, too, as do her cubs. The popular, livestreamed bears have about three months left to pack on weight before the winter famine begins.

SEE ALSO: There's a new giant king of the fat bears

For now, the young, skinny, defeated bear certainly needs to get fatter. But perhaps it won't attempt to again steal a 4,500-calorie salmon from Grazer.

"Not all fish are worth such a high price," said Fitz.