Every year, thousands of salmon make their way upstream along the nearly 2000-mile-long mighty Yukon River, desperate to reach spawning beds. Eagerly checking their progress is a host of hungry predators, from grizzly bears to bald eagles-all desperate to stock up on protein before the long winter months ahead.
Reptiles and amphibians look like hang-overs from the past. But they overcome their shortcomings through amazing innovation. The pebble toad turns into a rubber ball to roll and bounce from its enemies. Extreme slow-motion shows how a Jesus Christ lizard runs on water, and how a chameleon fires an extendible tongue at its prey with unfailing accuracy. The camera dives with a Niuean sea snake, which must breed on land but avoids predators by swimming to an air bubble at the end of an underwater tunnel. In a TV first, Komodo dragons hunt a huge water-buffalo, biting it to inject venom, then waiting for weeks until it dies. Ten dragons strip the carcass to the bone in four hours.
Can animals count? This is a question that has intrigued and fooled investigators for a long time. Just over 100 years ago, a German horse called Hans was declared a mathematical genius but all was not as it seemed. And strangely, some bamboos around the world flower exactly at the same no matter where they are. Are they counting down the years?
Many of the great rivers of southern Africa start high up in mountain ranges, power their way eastwards across wild forests and grasslands, and eventually empty out into the Indian Ocean. Ride the currents of these powerful bodies of water as they reshape the lives of the wild animals who rely on them.
Fortey travels to Madeira to examine what happens to a volcanic island as it nears the end of its life-cycle and starts sinking back into the sea. Here, in the island's laurisilva forest, he examines the remains of an ancient forest that once carpeted all of Europe, finds island lizards that live to be four times older than their mainland counterparts, and meets a huge wolf spider. With the help of local divers, he also discovers an unexpectedly rich marine habitat populated by whales, dolphins and unusual deep-sea species that have much to tell us about the changing nature of our seas.