The long-standing king of Alaska's Brooks River, Bear 856, killed a recently born cub along the river bank on July 3.。

The killing of the cub happened beyond view of the bear cams situated near the river's waterfall, where salmon collect and bears congregate, so streamed footage of the lurid event wasn't captured. However, the killing was photographed and confirmed by rangers as well as former Katmai National Park ranger Mike Fitz, who has returned to the river to report on bear activity for explore.org, which operates the wildlife cameras. 。

"Cubs face significant risks, and they are especially vulnerable in their first summer," Fitz said over email. "For me, this event is a powerful reminder of nature's harsh realities." 。

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Global viewers of the bear cam most often watch bears catching fish, sleeping, or exploring the river with their cubs. The bear world, however, can be quite violent, and infanticide events are not unknown — there have been 13 documented cases in 35 years at the Brooks River. In recent years, the killings have been witnessed by rangers, who've heard the yelps of a dying cub. 。

It's not fully understood why large males sometimes kill cubs, though there are compelling theories, detailed below. In this case, the event began when rangers watched Bear 856 assert his dominance by chasing another male bear (Bear 634) out of the river, as shown below. 。

Credit: explore.org/nps 。

Bear 856 then continued his pursuit downriver. A few minutes later, beyond the bear cams, violence unfolded when Bear 856 encountered, apparently by chance, a mother and her cubs.。

"The mother (132) tried to defend her cub, but 856 overpowered her and pinned her on her back," said Fitz. "856 saw vulnerability in the cub and the mother couldn't overpower the much larger bear."。

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With plenty of fish in the river, Bear 856 likely wasn't looking for an easy meal. 
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"The attack didn't seem motivated by hunger, either, as 856 didn't eat the cub," said Fitz, who believes "it was a product of chance more than anything else." 。

Bear 856's motivation won't ever be known, but at times, bears probably do have killing motives.
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There are three leading theories, detailed by Katmai National Park. The first is that a male bear's killing of a female's cub or cubs will force her back into heat, whereby she might be receptive to mating again. A nursing female, with newly born and helpless spring cubs, won't go into heat. Forcing a female back into heat may give that male bear more mating opportunities, and accordingly, increased opportunities to spread his genes.。

Bear 132 and her remaining cub, on July 5.Credit: explore.org / nps  。

The second possibility (strongly discounted in this case) is that bears aren't just the consummate omnivores, but they can be cannibals, too. Bears will do what it takes to fatten up for the long, cold winter hibernation. And sometimes, bears will kill and eat other bears. In some instances, cubs might be easy calories.。

Last, killing a cub reduces a bear's future competition — for females, fish, and territory. 。

Much of the bear world remains mysterious, to bear experts and bear cam viewers alike. But infanticide, above all, may be most perplexing. As the summer's salmon run is just ramping up, this is a stark early season reminder that, beyond the view of the bear cams — like the well-known waterfall and riffles cameras — there's an incessantly grim, competitive world.。

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"The cub's body was still lying in the grass near the riffles platform when I looked this morning," said Fitz.。

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"The cub's body was still lying in the grass near the riffles platform when I looked this morning," said Fitz. 。

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