The first episode illustrates a ‘journey’ around the globe and reveals the effect of gradual climatic change and seasonal transitions en route. During Antarctica’s winter, emperor penguins endure four months of darkness, with no food, in temperatures of –70°C. Meanwhile, as spring arrives in the Arctic, polar bear cubs take their first steps into a world of rapidly thawing ice. In northern Canada, the longest overland migration of any animal over 2000 miles is that of three million caribou, which are hunted by wolves, and one such pursuit is shown. The forests of eastern Russia are home to the Amur leopard: with a population of just 40 individuals, it is now the world’s rarest cat. This is primarily because of the destruction of its habitat, and Attenborough states that it “symbolises the fragility of our natural heritage.” However, in the tropics, the jungle that covers 3% of the planet’s surface supports 50% of its animals. Also depicted is the one-second strike of a great white shark as it pounces on a seal, slowed down forty times. Other species shown include New Guinea’s birds of paradise, African hunting dogs in their efficient pursuit of impala, elephants in Africa migrating towards the waters of the Okavango Delta, a seasonal bloom of life in the otherwise arid Kalahari Desert, and 300,000 migrating Baikal teal, containing the world’s entire population of the species in one flock. The Planet Earth Diaries segment shows how the wild dog hunt was filmed unobtrusively with the aid of the Heligimbal: a powerful, gyro-stabilised camera mounted beneath a helicopter.
 
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