Summer is the season of plenty for most animals, but not polar bears. Unable to hunt seals until the sea freezes over again, they grow hungrier by the day. For other animals summer is when youngsters must learn how to survive.
Intelligence and adaptability allow primates to tackle the many challenges of life, and this is what makes our closest relatives so successful. This resourcefulness has enabled primates to conquer an incredible diversity of habitat. Hamadryas baboons live on the open plains of Ethiopia in groups up to 400 strong. Strength in numbers gives them some protection from potential predators. But, should their path cross with other baboon troops, it can lead to all-out battle, as males try to steal females from one another, and even settle old scores. Japanese macaques are the most northerly-dwelling primates and they experience completely different challenges. Some beat the freezing conditions by having access to a thermal spa in the middle of winter. But this privilege is only for those born of the right female bloodline. For western lowland gorillas, it's the male silverback that leads his family group in the rich forests of the Congo basin. He advertises his status to all with a powerful chest-beating display. Most primates are forest dwellers, and one of the strangest is the tarsier – the only purely carnivorous primate. As it hunts for insects the tarsier leaps from tree to tree in the dead of night, using its huge forward-facing eyes to safely judge each jump. Good communication is essential for success in primate society.
Tanzania's Lake Manyara National Park boasts a number of diverse habitats. From woodland savannas to grassy marshes, the region is a special part of the east African ecosystem and provides a wealth of resources to the wildlife that call it home.
A humpback whale mother and calf embark on an epic journey from tropical coral paradises to storm ravaged polar seas. Newly discovered coral reefs in Indonesia reveal head-butting pygmy seahorses, flashing 'electric' clams and bands of sea kraits, 30-strong, which hunt in packs. Elsewhere plagues of sea urchins fell forests of giant kelp. Huge bull fur seals attack king penguins, who despite their weight disadvantage, put up a spirited defence.
Part two of two. Explorer Benedict Allen is determined to get disabled journalist Frank Gardner into the wilds of Papua New Guinea, despite having to grapple with Frank's wheelchair. As the terrain gets even tougher to negotiate, the pair know they must make an epic journey into the highlands, crossing through two tribal territories to achieve their objective. However, as Frank gets close to realising his dream of seeing wild birds of paradise up-close, his old injuries return to haunt him and the expedition hangs on a knife edge.
Dr Helen Czerski examines the hottest natural phenomena on the planet - lightning. Bolts of lightning five times hotter than the surface of the sun strike our planet over 3 million times every day - and yet we still know little about this deadly force of nature. Now, specialist photography is revealing how lightning travels through the air, high-speed cameras are unlocking the secrets of upward lightning that's triggered by our urban landscapes, and scientific expeditions are capturing rare images of intense electrical discharges over 80 kilometres wide.