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The Great Migration 3/6

Each year more than one million wildebeest and a quarter of a million zebra and gazelle migrate on Tanzania's Serengeti Plains – one of the most spectacular events in the natural world.

Nature's Great Events tells the story of the epic trek of herds that follow the rains to fresh pastures and the tale of the predators they leave behind.

The crew captures the desperate plight of a single pride of lions over an unprecedented year of filming to reveal a different side to the Serengeti.

Rather than being a predators' paradise – as it is so often portrayed – it's a land in constant change, with wildebeest following the rains and leaving the lions to tough it out.

When filming starts, the pride has seven cubs and is already suffering as the wildebeest leave their territory to find fresh pastures. Unable to follow, the four pride females struggle to find enough food for their hungry offspring.

To add to their struggle, a fire rages through the lions' territory destroying the cover they so desperately need in order to ambush the few prey animals that remain.

As weeks turn to months, the pride members become more emaciated and frailer, and the number of cubs dwindles to just two.

But for Serengeti's cheetahs, who use speed rather than ambush to catch their prey, the fire has created a perfect environment.

As the herds begin to return, the plains reveal one final secret. For the first time since 1967 the Serengeti's only active volcano – Ol Doinyo Lengai – begins to billow ash and smoke.

Using a gyro-stabilised helicopter mount, the team captures the action as lions and wildebeest are caught up in windblown dust and ash.

However, this event also reveals why the herds return each year in order to give birth. Fertilised by the volcanic ash over thousands of years, these short grass plains are among the most productive grasslands in the world.

After months of hardship the pride's tragic story was over as the herds returned providing plentiful food.

The producer is Peter Bassett.

Nature's Great Events Diary – Pride and Peril

When wildlife film-maker Owen Newman began following the Ndutu pride for Nature's Great Events he could not predict the harrowing tale he would be telling.

Despite his 20 years of experience filming big cats in Africa, the appalling condition of the cubs, battling to survive in a particularly harsh dry season, began to affect him more and more deeply.

Two of the youngest cubs had become separated from the pride. Hungry and alone, they lay all day calling for the adults who were too far away to hear.

The youngsters were so malnourished their hip bones jutted out, as well as their ribs; and their fur was falling out. They were painfully thin but their eyes were bright with the will to live.

It seemed almost disrespectful to capture such a scene on camera, so Owen finished filming as soon as he could and left them alone.

The following day he returned to where he had left them and was unable to find them or the rest of the Ndutu pride. He assumed the cubs had died and continued to search for the pride.

With no luck, he returned to the UK to wait until the beginning of the wet season before resuming the quest.

Once again, despite searching high and low, he was still unable to find the pride and assumed that none were left alive.

But finally, after weeks of searching, a local spotter reported a sighting and Owen raced to the scene.

Miraculously, it was the Ndutu pride with two healthy and well-fed cubs – one of which was the cub he thought he had filmed dying.

Episode Four: The Great Tide

As winter arrives along South Africa's east coast the inshore waters cool, drawing hundreds of millions of sardines northwards.

The sardine run is the world's largest marine spectacle, attracting the planet's greatest concentration of predators – an awe inspiring array of ocean hunters.

Super-pods of common dolphins up to 5,000 strong, thousands of sharks and huge Brydes whales feast on the sardines, as gannets rain down from above.

However, in recent years, the sardine run has become less than predictable.

It could be because of the effects of climate change warming the ocean. If the sardine run doesn't happen the lives of animals caught up in the drama hang in the balance.

Pioneering a unique boat stabilised camera mount, the Nature's Great Events crew were able to capture incredible new animal behaviours from the surface, as well as stunning footage of all the action from the air and underwater in HD.

But it required considerable persistence because of the unpredictability of the sardine run.

The story begins in the South African summer, a time when common dolphins and the gannets on the biggest gannet colony in the world – Bird Island – are raising their young.

The dolphins endlessly scour the ocean for fish, while unique footage captures the gannets' dramatic struggle for life as chicks are snatched by Cape fur seals racing on to the land.

A violent winter storm is the trigger for the sardines to begin their desperate dash. They are followed by a super-pod of 5,000 dolphins and further up the coast more predators gather.

A shoal of sardines 15 miles long is pushed into the shallows and thousands of sharks start to encircle them.

The climax to the sardine run is a spectacular feeding frenzy as the dolphins round the sardines up into balls on which all the predators feast.

Filming in super-slow motion captures every detail as gannets plunge into the water, hitting it at speeds of 60 miles an hour.

Aerial, underwater and surface cameras film the high octane action as the dolphins, sharks and Brydes whales' compete for the abundant prey.

The producer is Hugh Pearson.

Nature's Great Events Diary – Life On The Run

Didier Noirot, one of the most experienced underwater cameramen in the world, who worked with Jacques Cousteau for more than a decade, took on the task of filming the bait balls that characterise the sardine run.

The bait balls are incredibly short-lived and hard to find so it turned into a two-year mission for the Frenchman.

As well as the frustrations of no action and poor water visibility, Didier had to hold his nerve in the shark-infested waters.

First, they nipped his fins as he tried some novel in-water sound recording, then the sharks were strangely wary of Didier when he dropped in to film among thousands that were circling the sardine slick.

Undeterred by the sharks, he continued on the trail of the elusive bait ball. And it wasn't until the last week of filming in the second year that he found himself in the perfect position – among a feeding frenzy in ideal filming conditions.

Astonishing footage of Didier in the heart of the action gives a real sense of scale and context, but being that close can be risky.

A 16-foot shark took a lunge at his leg but he was able to fend it off before it took a bite.

"The sharks were too aggressive... we got bumped a few times... and that was a bit serious," he admits.

But he held his nerve to capture unique footage on the penultimate day of the filming.