Nature Shock Season 3

Exploring the life of the killer whale. Streamlined and cunning, killer whales have many hunting techniques. They live and hunt together in cooperative pods much like a pack of wolves, and work together as they hunt. Groups of orcas cooperate to herd fish into a compact area so that they're easier to eat. They will also slap their tails onto the water's surface, causing a wave to wash prey off ice floes and into the water. A pod will also surround a much larger animal, chasing, biting and wearing it down until it becomes a meal. They’ve also been seen playing with a meal, subjecting the poor victim to torment before eventually eating it - isolated, outnumbered and overwhelmed, their prey stands no chance.

This instalment details how a strange series of seal mutilations baffled experts for over a decade. The shocking discovery of the unlikely culprit turned marine biology on its head.

This instalment tells the story of how a dramatic decline in the vulture population has caused ecological disaster in India. The shrinking number of vultures has damaged the country's fragile ecosystem, and has kick-started a shocking chain of events, including an explosion in rabies cases and a marked increase in fatal leopard attacks.

This instalment profiles the shocking advance of the Humboldt squid. Since 2002, these fearsome predators have colonised the seas at an alarming rate, destroying ecosystems and disrupting fisheries. Researchers around the globe are racing against time to find ways of halting this devastating invasion.

On August 21, 1986, nearly 2,000 people living near Lake Nyos in north-west Cameroon dropped dead, severely depleting the populations of three lakeside villages. The documentary examines the circumstances surrounding the tragedy, questioning whether the eruption of carbon dioxide pockets at the bottom of the lake could have produced an odourless toxic cloud deadly enough to suffocate the locals

An examination of the media uproar that surrounded the deaths of five elephants near a Bengali village in May 2007. Intensive investigations concluded the creatures were killed by a lightning strike during a fierce electrical storm, but some experts remained unconvinced. This programme explores allegations of foul play by the Indian state's Forest Department, and questions whether the animals could have been poisoned

Examination of the spate of deaths among Ugandan hippos that occurred in 2004. Though tests quickly confirmed they were being poisoned by anthrax, how it was spread astounded vets - noting that unusually no other species were affected by the outbreak, it became evident the creatures were catching the illness by eating the corpses of their kind as drought destroyed their regular sources of nutrition

In 1997, tourists on a whale-watching boat 27 miles west of San Francisco were stunned to see a great white shark being attacked, killed and eaten by an orca, effectively deposing the former as the marine world's most feared predator. Using footage from the incident, experts provide their theories as to how the killer whale was able to overpower its adversary, and question whether this event warrants a reconsideration of the ocean's food chain