Planeta Tierra es una aclamada serie de documentales creada por la BBC que nos muestra, en 11 episodios escritos por el prestigioso naturalista David Attenborough, la belleza de nuestro enorme planeta con imágenes nunca antes vistas. 7. "Great Plains" UK broadcast 12 November 2006, 6.72 million viewers (24% audience share);[25] 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. Over Africa's savanna, a swarm of 1.5 billion Red-billed Queleas are caught on camera, the largest flock of birds ever depicted.[32] 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 African bush 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.