UK broadcast 12 November 2006, 6.72 million viewers (24% audience share); US broadcast 8 April 2007
This episode deals with savanna, steppe, tundra, prairie, and looks at the importance and resilience of grasses in such treeless ecosystems. Their vast expanses contain the largest concentration of animal life. In Outer Mongolia, a herd of Mongolian gazelle flee a bush fire and has to move on to new grazing, but grass can repair itself rapidly and soon reappears. On the Arctic tundra during spring, millions of migratory snow geese arrive to breed and their young are preyed on by Arctic foxes. Meanwhile, time-lapse photography depicts moving herds of caribou as a calf is brought down by a chasing wolf. On the North American prairie, bison engage in the ritual to establish the dominant males. The Tibetan Plateau is the highest of the plains and despite its relative lack of grass, animals do survive there, including yak and wild ass. However, the area's most numerous resident is the pika, whose nemesis is the Tibetan fox. In tropical India, the tall grasses hide some of the largest creatures and also the smallest, such as the pygmy hog. The final sequence depicts the African savannah and elephants that are forced to share a waterhole with a pride of thirty lions. The insufficient water makes it an uneasy alliance and the latter gain the upper hand during the night when their hunger drives them to hunt and eventually kill one of the pachyderms. Planet Earth Diaries explains how the lion hunt was filmed in darkness using infrared light
A Costa Rican tree frog
UK broadcast 19 November 2006, 7.04 million viewers (26% audience share); US broadcast 15 April 2007
The next instalment examines jungles and tropical rainforests. These environments occupy only 3% of the land yet are home to over half of the world's species. New Guinea is inhabited by almost 40 kinds of birds of paradise, which avoid conflict with each other by living in different parts of the island. Some of their elaborate courtship displays are shown. Within the dense forest canopy, sunlight is prized, and the death of a tree triggers a race by saplings to fill the vacant space. Figs are a widespread and popular food, and as many as 44 types of bird and monkey have been observed picking from a single tree. The sounds of the jungle throughout the day are explored, from the early morning calls of siamangs and orangutans to the nocturnal cacophony of courting tree frogs. The importance of fungi to the rainforest is illustrated by a sequence of them fruiting, including a parasite called cordyceps. The mutual benefits of the relationship between carnivorous pitcher plants and red crab spiders is also discussed. In the Congo, roaming forest elephants are shown reaching a clearing to feed on essential clay minerals within the mud. Finally, chimpanzees are one of the few jungle animals able to traverse both the forest floor and the canopy in search of food. In Uganda, members of a 150-strong community of the primates mount a raid into neighbouring territory in order to gain control of it. Planet Earth Diaries looks at filming displaying birds of paradise, focusing mainly on the filming of the six-plumed bird of paradise
9. "Shallow Seas"
UK broadcast 26 November 2006, 7.32 million viewers (28% audience share); US broadcast 8 April 2007
This programme is devoted to the shallow seas that fringe the world's continents. Although they constitute 8% of the oceans, they contain most marine life. As humpback whales return to breeding grounds in the tropics, a mother and its calf are followed. While the latter takes in up to 500 litres of milk a day, its parent will starve until it travels back to the poles to feed — and it must do this while it still has sufficient energy left for the journey. The coral reefs of Indonesia are home to the biggest variety of ocean dwellers. Examples include banded sea kraits, which ally themselves with goatfish and trevally in order to hunt. In Western Australia, dolphins 'hydroplane' in the shallowest waters to catch a meal, while in Bahrain, 100,000 Socotra cormorants rely on shamals that blow sand grains into the nearby Persian Gulf, transforming it into a rich fishing ground. The appearance of algae in the spring starts a food chain that leads to an abundant harvest, and sea lions and dusky dolphins are among those taking advantage of it. In Southern Africa, as chokka squid are preyed on by short-tail stingray, the Cape fur seals that share the waters are hunted by the world's largest predatory fish: the great white shark. On Marion Island in the Indian Ocean, a group of king penguins must cross a beach occupied by fur seals that do not hesitate to attack them. Planet Earth Diaries shows the difficulties of filming the one-second strike of a great white shark, filmed by Simon King