It had all the hallmarks of an impending ecological disaster: a crippled oil tanker, rough seas and a vulnerable population of sea birds. But when the stricken crude oil carrier, 'The Treasure', was towed and sunk six kilometres from Cape Town harbour, no one could have anticipated the remarkable rescue operation that swung into action to save the world's third biggest colony of African penguins from an oily death.

In 'Rescue', Earth Report follows the story of the disaster and recovery as it happened.

That sinking feeling

In June 2000, an oil tanker carrying 1300 tonnes of crude oil asked to be allowed into South Africa's Cape Town harbour. When it arrived, maritime safety authorities noticed a large tear in its hull. Fearing it might sink, the ship was towed out to sea and sunk - causing oil to spill out. The very next day penguins covered in oil came ashore on Robben Island.

To the rescue

The chief victim of the disaster was the African penguin. Classified as 'vulnerable', the Southern African sea is home to 40,000 of the total world population of 160,000 birds. If rescuers failed to save the two large breeding colonies on Robben Island and Dassen Island - almost one quarter of the world's population of African penguins would be lost.

To save these birds would be a mammoth task. As a preventative action, unoiled penguins would have to be captured and removed from the polluted area whilst oiled birds would need to be removed and taken to a special treatment centre.

Other species under threat were cormorants and black oystercatches. Out of the four species of cormorant on the South African coast, two are extremely rare: the bank and the crown cormorant.

Since the last major oil spill to pollute this part of the South African coast the conservation agencies here have learnt how to capture and care for oiled birds. A major improvement has been the specially designed boxes for transporting captured penguins. During previous spills most mortalities occurred during transportation.

But the real task began when the birds arrived at The South African Foundation for the Conservation of Coastal Birds (SANCCOB) Centre at Reepfly near Cape Town.

The big clean-up

As each bird arrived at the treatment centre, experts assessed them for dehydration before treating them for oil poisoning - which ulcerates the stomach walls causing gastro-anaemia.

Next, the scientists fed a compound of activated charcoal and kaolin into the stomach of each penguin to bind together toxins and line the walls of the stomach and intestines. An injection of iron combatted anaemia.

Each bird was then washed. Washing the oil off is the critical part of the rehabilitation process. Oil destroys a bird's waterproofing by causing it's feathers to clump together - leading to hypothermia in cold seawater. An oiled bird will not hunt but mobilise its fat resources and eventually dehydrate and die.

Washing a penguin can take between 20 - 30 minutes each and, with more than 20,000 penguins waiting to be cleaned, conservationists worked around the clock.

Critical to the success of this operation were the volunteers. Overnight, large sections of the South African population mobilised into action, giving much needed help to the stretched SANCCOB team.

A second crisis

On day six the drama escalated dramatically. Several oil slicks threatened to engulf the biggest single breeding colony of African penguins on Dassen Island - home to close to half of the title world population of penguins. The rescue effort went into top gear.

Now conservationists were facing a terrible dilemma. If they evacuated the penguins as a precaution and the oil never reached the island they would unnecessarily have caused the deaths of thousands of chicks - and that could seriously set back an already vulnerable species.

A decision was made to fence the penguins inside the island so that they couldn't swim into polluted areas, whilst removing as many adult penguins to Port Elizabeth.

With a population of between 50,000 - 60,000 adults and chicks, it was impossible to evacuate the whole colony. As a matter of survival priorities, scientists decided to focus on removing breeding adults, not chicks. As only around 10 - 15% of chicks survive their first year, survival of the colony depended on saving adults - which can breed 2 - 3 times a year for up to 20 years.

In the first three weeks after the oil carrier sank, 21,000 penguins were transported from the two island colonies to Port Elizabeth and released at Cape Rosief, a thousand kilometres away from the oil slicks. Scientists knew that the remarkable homing instinct of penguins would take them back to their breeding colonies - but they would have around 20 days to feed en-route in unpolluted waters. To help them track their progress back to the breeding colonies, three of the penguins, Peter, Pamela and Percy, were fitted with flipper satellite transmitters.

Hundred of thousands of people followed the progress of the three penguins on the internet as they made their way, non-stop, back to the Cape. Twenty days after their journey started, the first penguins arrived back.