In the final episode of this groundbreaking scientific study, Liz Bonnin and a team of scientists reveal the secret language of our cats, the surprising conversations they have when we are asleep, and why they meow to us but not each other. We rig a house with cameras and cat trackers to discover if four cats living under one roof all get on as well as we would like to think. And we find out why living alongside us is making life difficult for our 21st-century cats.
The Namaqua rock fig is known as the rock splitter. It's not just a testament to its ability to withstand the dry conditions, but a literal tribute to its powerful root system, which extends 200 feet into the Earth in search of water. Besides the army of wildlife who rely on it for survival, the rock splitter has a unique relationship with its own species of miniature wasp that help pollinate its tiny flowers. As temperatures soar each passing year, this ultimate survivor reaches deeper to squeeze every drop of water from the parched land.
Marine invertebrates are some of the most bizarre and beautiful animals on the planet, and thrive in the toughest parts of the oceans. Divers swim into a shoal of predatory Humboldt squid as they emerge from the ocean depths to hunt in packs. When cuttlefish gather to mate, their bodies flash in stroboscopic colours. Time-lapse photography reveals thousands of starfish gathering under the Arctic ice to devour a seal carcass. A giant octopus commits suicide for her young. A camera follows her into a cave which she walls up, then she protects her eggs until she starves. The greatest living structures on earth, coral reefs, are created by tiny animals in some of the world's most inhospitable waters.
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.
In the thick of the jungle of Rwanda's Volcanoes National Park, an infant mountain gorilla has been caught in a snare. If the rope is not removed quickly enough, the young gorilla could lose its hand. In order to remove the snare, a team of veterinarians will first need to sedate the infant's mother. But if the infant screams too much, the three 400-pound adult males that form part of this gorilla group will all attack. Everything must go perfectly, or there's no telling what could happen. And being jungle medicine, things rarely go perfectly. The pioneering group of vets performing this medical intervention is known as Gorilla Doctors. Led by Canadian Mike Cranfield, they work in Rwanda, the Democratic Republic of Congo and Uganda, where the world's last Mountain Gorillas can be found.