PUKE

Two journalists traverse the Grand Canyon by foot, hoping this 750-mile walk will help them better understand one of America's most revered landscapes and the threats poised to alter it forever.

The grasslands of Africa are a banquet spread for feline predators. Explore the hunting and nurturing habits of lions, leopards, and cheetahs of the African savannah, as well as the overlooked grasses that lay the foundation for the amazing array of wildlife flourishing among its leaves.

This documentary examines the threatened habitats and the three great predators: the jaguar, the leopard and the cheetah, of the great South American jungle, the Masai Mara grasslands of Kenya and the bushland of South Africa.

A dive inside a wild land where nature hides some of her greatest secrets: The Alps. Steep slopes, wind swept cutting edge rocks. An air desperately lacking of oxygen. A biting cold. How do living beings adapt to those extreme conditions?

A group of scientists are thinking outside the box for ways to reverse the effects of global warming. And who better to save the earth than National Geographic Channel's host of the World's Toughest Fixes, Sean Riley? He'll join these experts in the labs and in the field to see what wacky new technologies are being developed, like sending mirrors into space and reducing the greenhouse emissions chickens produce.

In 2009 a team of British cavers went on an expedition deep within the jungle of central Vietnam. To their amazement they discovered an enormous cave which they believe to be the biggest in the world. The team, the first humans ever to enter the cave, traveled 6 kilometers underground until their way was blocked by a gigantic rock face they dubbed 'The Great Wall of Vietnam'. Now they have returned, but this time with the right equipment to climb the wall and with a geologist and zoologist to discover if this is indeed the Biggest Cave in the World and what secrets lie deep within?

See the world's first MRI scan of a great white shark as Ultimate Shark reveals the extreme engineering and predatory abilities of one of nature's most near perfect predators. Hear firsthand accounts of people who survived harrowing encounters, including a surfer who was bitten on the arm and leg, towed by the surfboard ankle strap and miraculously escaped only with minor injuries. National Geographic demystifies the true motives and power behind their behavior.

Peter Gimbel and a team of photographers set out on an expedition to find and film, for the very first time, Carcharodon carcharias—the Great White Shark. The expedition lasted over nine months and took the team from Durban, South Africa, across the Indian Ocean, and finally to southern Australia.