Nature's Great Events

The summer melt of Arctic ice provides opportunities for millions of animals, but grave dangers for others, including polar bears.

A spectacular natural event takes place in North America every year as hundreds of millions of salmon return from the Pacific Ocean to the mountain streams where they were born. The salmon must overcome fierce torrents and leap over waterfalls as they make their way upstream. The great run not only provides food for bears, but for killer whales, wolves, bald eagles and even for the forest itself. A family of bears is filmed from the air as they make a treacherous journey to the coast to await the return of the salmon.

Each year over a million wildebeest and zebra invade the Serengeti grasslands making it a paradise for the predators that live there. But what happens when the herds move off again? We follow the moving story of one lion family's struggle to survive until the return of the great migration. The Ntudu pride has seven cubs and is already suffering as the wildebeest leave to find fresh pastures. As weeks turn to months, the pride members become more emaciated and frailer. Then finally as the herds begin to return, the plains reveal one final secret.

A mighty army of dolphins, sharks, whales, seals and gannets hunt down billions of sardines along South Africa's east coast each winter. This is the Sardine Run: an underwater armageddon, the greatest gathering of predators anywhere on the planet, and the most spectacular event in the world's oceans. Pioneering a unique boat stabilised camera mount for surface filming, the crew capture all the high octane action as the predators compete for sardines, filmed with aerial, underwater and above water cameras.

The Great Flood in the Okavango turns 4000 square miles of arid plains into a beautiful wetland. Elephant mothers guide their families on an epic trek across the harsh Kalahari desert towards it, using their trunks to siphon fresh water from stagnant pools along the way. Hippos battle for territory, as the magical water draws in thousands of buffalo and birds, and vast clouds of dragonflies. As the flood finally reaches its peak, elephants and buffalo, near the end of their epic trek across the desert, face the final gauntlet of a hungry pride of lions.

Every summer in the seas off Alaska humpback whales, sea lions and killer whales depend on an explosion of plant life, the plankton bloom. It transforms these seas into the richest on Earth. But will these animals survive to enjoy the great feast? Filmed from the surface, underwater and - for the first time - from the air, we reveal how giant the humpback whales can catch a tonne of fish every day.