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The various challenges that the cold and snow of winter pose for the animals that live in Yellowstone are explored.

Having been reintroduced to Yellowstone in 1995 after a 70-year absence, wolves have reignited an age-old battle between predator and prey. The Wapiti Pack, the largest in Yellowstone, has earned a reputation for ferocity. Now a young, lone wolf, “Blacktail,” seeks to join their ranks as they master the art of taking down a mighty bison. But wolves aren’t the only force keeping Yellowstone’s herds in check. The endangered Yellowstone grizzly population has made a remarkable comeback, rising from a low point of fewer than 150 bears to more than 700 today. Many are descendants of legendary matriarch “Quad-Mom,” who, at more than 20 years old, is raising two new cubs – perhaps the last of her litters. She must defend the cubs against giant boar grizzlies and teach the cubs to hunt newborn elk. As the family ventures to the high alpine in search of a rare treat, darkness descends on Yellowstone during a total solar eclipse.

Soaring above Old Faithful, the cascading Lower Falls and the brilliant Grand Prismatic Springs, Yellowstone’s winged creatures survey an extraordinary landscape. Winter’s silence is broken only by the song of the American dipper, North America’s only aquatic songbird, which feasts on tiny insects gathered from the river bottom. Spring heralds a dramatic chorus as seasonal migrants flock to the park, nesting in every niche provided by its mosaic of forests, grasslands and wetlands. Breeding sandhill cranes perform their annual courtship dance as they renew lifelong partnerships with their mates. Summer brings opportunities for birds to take advantage of the season’s bounty alongside bears and bison as the park’s wildlife population swells with new arrivals. A pair of bluebirds works feverishly to deliver food to two consecutive broods nestled inside a treehole, while an osprey fends off a peregrine falcon’s attack to defend his catch.

The Yellowstone River moves untamed through its 700-mile journey. In the heart of winter, trumpeter swans congregate at the river’s outlet on Yellowstone Lake’s northern end, sheltering in its geothermally warmed waters. The river’s biggest vertical drop over the iconic Upper and Lower Falls poses a danger for even the strongest swimmers – a family of river otters makes a daring portage down the cliffs to reach fishing grounds at the bottom of the waterfall. Spring’s thaw unleashes millions of gallons of meltwater and transforms the tranquil river into a raging torrent, forcing a sow grizzly and bison herd to ford treacherous rapids while protecting their young. Summer brings an easier flow to the river as it leaves the confines of the park and winds through Paradise Valley. The river leaves the mountains behind and enters the prairie, where new creatures emerge – distant echoes from the muddy Mississippi that grow stronger as the river’s journey nears its end.