Going down into these narrow flooded passageways is not for the faint-hearted but, with only an estimated one percent of the caves explored, it is an opportunity for the team to write themselves into cave diving history, by pushing further in than anyone has before. This is a challenge that tests even the most accomplished cave divers. Steve must face the terrors of being lost in an underwater silt cloud in a cave. But there is a bigger issue at stake. All life in the Yucatan depends on the fresh water in this network of caves, but it's being contaminated by human development. With every metre the team maps, it adds to the knowledge of the system, which, in turns, helps protect it for future generations.
The fifth programme explores the alliances formed between the animal and plant worlds. It examines the ways in which plants live together and rely on each other. Whether living together in harmony, relying on each other for homes, protection or food, or living off each other, by strangling or otherwise destroying each other in a bid to survive.
What is it that makes things alive? What if we made robots that could sustain themselves? What if they could mine metals or recycle old robots, reprogram and remake themselves? There's nothing there we would traditional call alive, but they would have at least have the essence of this perpetual rube Goldberg machine.
Professor Richard Fortey investigates the remains of ancient volcanic lake in Germany where stunningly well-preserved fossils of early mammals, giant insects and even perhaps our oldest known ancestor have been found. Among the amazing finds are bats as advanced and sophisticated as anything living today, more than 50-million-years-later; dog-sized 'Dawn' horses, the ancestor of the modern horse; and giant ants as large as a hummingbird.
The Arctic region of Russia is considered the most inhospitable places to live. But polar bears, lemmings, Arctic foxes, and seals - Arctic - simply heaven. In late August, with the onset of the breeding season is going very strong male musk for traditional competitions for the right leadership in the pairing with females. Weight of an adult bull can reach 400 kilograms. In a skirmish with a rival musk ox to deliver a decisive blow running away at 40 miles per hour. Sound from the blow horns fighting males can be heard at a distance of more than one kilometer.
This vibrant new Nature special explores the astonishing survival techniques of butterflies, including their 360 vision, deceptive camouflage, chemical weaponry, and fantastic flight across continents. Through sophisticated macro-filming, viewers get a rare glimpse beyond the butterflies’ bright colours and fragile beauty as they follow them on one of the greatest migrations on Earth. Narrated by Paul Giamatti.