The hypnotic sex videolivestream of Alaska's fat bears is unfiltered. It can be brutal.

On July 27, one of the largest and most dominant bears of Katmai National Park and Preserve's Brooks River attacked a cub, to the dread of web onlookers. The cub looked seriously injured, appeared to slightly improve over a couple of days, but ultimately died in the river. It's an event that reveals the bears' natural world in its full, wild spectrum.

"We get to see their moments of joy," Mike Fitz, a former Katmai park ranger and currently a resident naturalist for the bear cam livestreamers explore.org, said in an online live chat. "However, the webcams are live, the footage is uncensored. We also see bears face hardship, hunger, injury, pain, and even death."

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These bears, living remote lives on the Alaskan Peninsula where visitors arrive aboard small floatplanes, are beamed to the world with the aid of radio transmitters. Katmai's bears have grown internet-famous in the park's annual Fat Bear Week contest, an event celebrating the success of these persevering animals in the harsh wilderness. They must devour salmon throughout the summer to build enough fat stores to outlast the long winter famine, when they hibernate. That's why a fat bear is a healthy bear.

In July, bears congregate in the park's Brooks River to capitalize on these prodigious runs of salmon — bringing the often solitary animals in crowded, close proximity. It's here where the attack occurred.

The well-known mother bear Grazer — who was last year's Fat Bear Week champion — was fishing atop a waterfall with her two spring cubs (meaning they were just born this year). This was a somewhat risky endeavor, because the current is strong. Soon enough, both young bears fell over the falls, and one passed near the large male bear 32, "Chunk," an animal in his prime whose dominance affords him the most productive fishing spots. For reasons unknown, Chunk went after and attacked the cub, as shown in the screenshot below. He clenched the small bear in his jaws.

But the drama didn't end there. Grazer sprinted to defend her cub.

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In this screenshot from the livestream, the cub appears to be in Chunk's jaws, while Grazer (on left) aggressively seeks to intimidate Chunk. Credit: NPS / explore.org

Grazer is a particularly aggressive bear, who has previously charged bears that came close to her cubs, and even mauled a bear that attempted to steal a fish. It's this fearless aggression, against a dominant bear hundreds of pounds larger than her, that likely spared the cub an abrupt fatal injury. Numerous times, Grazer forced Chunk to back off.

"She's courageous — she's defensive."

"She continued to fight back," Naomi Boak, who covers the bears for the Katmai Conservancy, an organization supporting the national park, said during the live chat. "She's courageous — she's defensive."

You can watch the encounter below, from 12:20 to 14:30.

Although the cub appeared severely injured following the attack — bawling, licking its paw, and moving little — the young bear persevered in the aftermath, though it eventually succumbed to injuries. On August 2, webcam watchers saw the dead cub float over the waterfall. The lifeless animal passed directly in front of Grazer.

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Even so, the cub gave an ardent effort to live. It survived the encounter and made it to the relative safety of the riverbank, where it attempted to convalesce. "Cubs are tough," Fitz told Mashable over email. Katmai cubs face many threats — attacks, illness, drowning, insufficient nutrients — and have about a 34 percent survival rate at Katmai.

"Cubs are tough."

We'll never know why Chunk opportunistically attacked the cub. Prior to the cubs falling, Chunk expressed no interest in Grazer's family; rather, he was focused on capturing 4,500-calorie sockeye salmon. Large males have killed bears on the livestream before. It could simply have been an instinctual reaction. It's possible, as in other cases of bear infanticide, Chunk intended to send a potentially cub-less Grazer back into estrus, a form of sexual selection (though this doesn't add up when considering his previous disinterest in the family group). Chunk might have felt he was competing with Grazer's family for food. Or perhaps it's a reason our species can't understand or imagine.

The Katmai bears will continue fighting for survival on the bear cams. It's a dynamic view into a largely untrammeled realm. It's a world that is at once beautiful and ruthless.

"National parks such as Katmai exist to protect and preserve wild landscapes and ecosystem processes," Fitz said. "This includes the grand spectacles such as bears fishing at Brooks Falls and nature's harsh realities."

UPDATE: Aug. 5, 2024, 12:19 p.m. EDT This story was originally published on Aug. 3, 2024 and updated to add new details about the death of the bear cub. Mark Kaufman contributed to this update.