For the animals in the polar regions, autumn means dramatic battles and epic journeys. Time is running out - the Arctic Ocean is freezing over and the sea ice is advancing at 2.5 miles per day around Antarctica. Polar bears gather in large numbers on the Arctic coast as they wait for the return of the ice. Soon, tempers fray and violent sparring contests break out. Meanwhile 2,000 beluga whales head for one special estuary, a gigantic 'whale spa' where they will thrash their snow-white bodies against the gravel and exfoliate. Inland, the tundra undergoes a dramatic transformation from green to fiery red. Here, musk ox males slam head-first into each other with the force of a 30mph car crash as they struggle to defend their harems. Frisky young caribou males play a game of 'grandma's footsteps' as they try to steal the boss's female. Down in Antarctica, Adelie penguin chicks huddle together in creches. When a parent returns from fishing, it leads its twins on a comical steeplechase - sadly there's only enough for one, so the winner gets the meal. Two months later and the chicks are fully feathered apart from downy Mohican hairdos - they're ready to take their first swim - reluctantly though, as it seems penguins are not born with a love of water! And with good reason - a leopard seal explodes from the sea and pulls one from an ice floe, a hunting manoeuvre that has never been filmed before. As winter approaches and everyone has left, the giant emperor penguin arrives and makes an epic trek inland to breed. The mothers soon return to the sea leaving the fathers to hold the eggs and endure the coldest winter on earth.
Known as "the roof of Africa," the Simien Mountains offer a glimpse at some of the rarest creatures on the continent. Among plunging cliffs that give way to lush greenery and foggy skies, learn how native wildlife like the magnificent walia ibex and cunning Simien wolf have adapted to this remote alpine terrain.
Details coastal environments and the effect of tides, of which the highest can be found in the Bay of Fundy in North America. In places, erosion is causing the land to retreat, while in others — such as the tropics — the expansion of mangroves causes it to advance.
Begins in northern Norway, 500 kilometres north of the Arctic Circle. Here, there is only just enough light for the pine trees to survive, but it is extremely cold during the winter. Pine cone seeds provide one of the few foods available at this time of year, and large herbivores such as the moose must also rely on their fat reserves.