Polar bear cub's agonizing struggle in Netflix's 'Our Planet II' is telling 'heartbreaker'

Netflix's "Our Planet II" nature series is filled with stunning moments of Earth's wildlife on the move.

The four-part follow-up to 2019's "Our Planet" explores the mystery of animal migration and the impact of climate change, highlighting wild elephants trekking on an arduous two-year journey into China, Biblical swarms of continent-crossing locusts and a massive nesting turtle event on Escobilla Beach in Mexico.

But it was the scenes of a desperate hunt by a polar bear family ― and one eight-month-old cub's plaintive travails ― that pulled on the heartstrings of narrator Sir David Attenborough when the wildlife documentary legend saw the footage.

He "singled that out, saying the polar bear scenes were a real heartbreaker, and that it would capture people's imaginations," says field producer Ed Charles. "This was a family on the edge. It was very emotional to watch in person. And it's an important story."

Here's the tumultuous polar bear cub saga from "Our Planet II" (now streaming).

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Charles and his team found the polar bear family at the end of a nearly fruitless three-week search in the Arctic Ocean island chain of Svalbard. During the mother's increasingly desperate search for scarce food, the starving family was forced to use precious energy swimming between rocky islands due to melting sea ice.

NASA scientists have determined through satellite imagery that summer Arctic sea ice is shrinking by 12.6% each decade as a result of global warming.

"This mother and her cubs should have been hunting on the ice, even broken ice. That's where they're supremely adapted to be," says Charles. "But we found them in water that was open for as far as the eye could see. That's the reality of the world they live in today. Nature can be brutal. But to see this family with the cub, struggling due to no fault of their own, it makes it very hard."

The second, weaker cub labors trying to keep up in the hours the crew filmed by boat, cut down to minutes in "Our Planet II." The scene came to an emotional climax on a craggy island as the cub strained to pull itself ashore and then labored up the rock face.

"Everyone watched with their hearts in their mouths," says Charles, adding that even experienced crew members became more distressed when the exhausted cub panicked after losing sight of its mother. "I mean, it was really screaming. You could hear it coming across the water."

But the cub rallied to join its family.

"Somehow it got a foothold and pushed to another and another, screaming the whole time," says Charles. "And when it finally made it up, the whole boat erupted, punching the air and weeping."

The joy was short-lived, as the cubs discovered the island lacked prey. The starving family was forced to immediately return to the water to swim and seek another location for food. The still-weakened cub was last seen working to keep up with its mother in the water.

"When we film something poignant, sometimes upsetting, we don't have the answers of what happened next," says producer Keith Scholey. "That sort of uncertainty can be comforting for viewers."

But the scenes resonate because they demonstrate the role of global warming caused by humans, says producer Huw Cordey.

"It's a sign of the times," he says. "This is an emotional story that's partly of our own making."

This article originally appeared on USA TODAY: Netflix's 'Our Planet II' reveals polar bear cub's emotional struggle