Sir David Attenborough narrates this 46:59 documentary and second in the acclaimed series. All the main mountain ranges are explored with extensive aerial photography. Ethiopia's Erta Ale is the longest continually erupting volcano — for over 100 years. On the nearby highlands, geladas (the only primate whose diet is almost entirely of grass) inhabit precipitous slopes nearly three miles up, in troops that are 800-strong: the most numerous of their kind. Alongside them live the critically endangered walia ibex, and both species take turns to act as lookout for predatory Ethiopian wolves. The Andes have the most volatile weather and guanacos are shown enduring a flash blizzard, along with an exceptional group sighting of the normally solitary puma. The Alpine summits are always snow-covered, apart from that of the Matterhorn, which is too sheer to allow it to settle. Grizzly bear cubs emerge from their den for the first time in the Rockies, while Himalayan inhabitants include rutting markhor, golden eagles that hunt migrating demoiselle cranes, and the rare snow leopard. At the eastern end of the range, the giant panda cannot hibernate due to its poor nutriment of bamboo and one of them cradles its week-old cub. Also shown is the Earth's biggest mountain glacier: the Baltoro in Pakistan, which is 43 miles long and visible from space. Planet Earth Diaries demonstrates the difficulty of obtaining the first ever close-up footage of the snow leopards: a process which took over a year.