By Charles Colville
There are only thirteen northern white rhinos left in the world. The species is hovering on the brink of extinction. But three men are pushing forward the frontiers of science to try to save them.
The northern white rhino is under threat in the wild
Thomas Hildebrandt and his team, from the Berlin Institute of Zoo and Wildlife Research, are world leaders in using artificial reproduction to breed rare elephants, rhinos and even komodo dragons.
Their work has never been more urgent. Throughout the history of Earth, 99% of all species which ever existed have disappeared. It is called the natural rate of extinction.
But now scientists think human activity is causing species to disappear at up to 10,000 times this rate. Many claim the last time this happened was 65 million years ago, when the dinosaurs died out.
The great conservationist Richard Leakey has called it "the Sixth Mass Extinction".
Only one northern white rhino baby has been born in the last six years. Now, the Berlin team is working with six captive animals, at the Dvur Kralove Safari Park, 110km (70 miles) north-east of Prague, in the Czech Republic.
Last summer, they inseminated Fatu, one of only two fertile females in captivity.
She had not been ovulating and needed hormone injections to get her cycle started. Months later, the results came in and unfortunately she did not get pregnant.
"Despite the setback, we have to continue and we are very determined," says Dr Hildebrandt. "We know that the work that we do is very important."
Dr Hildebrandt is now convinced that artificial insemination alone will not save the species, so he is developing a ground-breaking IVF technique.
Captive breeding programmes will reduce dependence on wild animals
Working with an international team from the Netherlands, Australia and China, he has already successful collected an oocyte, or egg, from a female of the more numerous southern white rhino species, at Western Plains Zoo, in New South Wales.
The egg was fertilised in vitro, in a test tube, to produce an IVF rhino embryo.
"Reproduction technology is increasingly important for saving species," says Dr Hildebrandt, who knows that time is running out.
Later this year, the team will start to harvest eggs from the northern white rhino in the Czech Republic, and if all goes well, create baby northern whites. With so few northern white rhinos remaining, the researchers hope to use southern white rhinos as surrogate mothers.
Dr Hildebrandt and his colleague Frank Goeritz were brought up in the former East Germany. They both suffered under the former communist regime and were initially not allowed to attend university, because of their middle-class background.
Instead, they had to work as porters in an agricultural vet college. However, Dr Hildebrandt persuaded the head of the institute to allow him to study for a degree. That is when he started work on artificially inseminating cattle.
Within a few years, the zoologist was working with wild animals. Such was his passion for the subject that when the Berlin wall came down in 1989, he was too busy inseminating rare animals at the East Berlin Zoo to join the millions of his compatriots crossing to the West.
Since then, the team has travelled ceaselessly across the world. Zoos and conservation projects from Australia to California have requested their services to boost breeding programmes.
However, the German scientists often confront unexpected obstacles on their travels.
Last October Dr Hildebrandt collected semen from a male elephant at Pittsburgh Zoo, to use for inseminating a female elephant 3,000km away in Salt Lake City.
The semen had to be placed in carry-on baggage, to avoid it being exposed to extreme temperatures or cosmic rays.
Captive breeding of rhinos is far from a straightforward business
At the time, liquids could not be transported on American planes, following the attempted terrorist attacks on transatlantic planes in August 2006.
Initially, airport security refused to give the go ahead and the project appeared doomed. Only after the intervention of the head of Pittsburgh Zoo did airport security officials relent, and allow Dr Hildebrandt and his elephant semen on board the plane.
But even then, Dr Hildebrandt, and the elephant semen, had to be escorted by a bodyguard through the airport. Happily, the semen arrived within the eight-hour deadline, just in time to inseminate Christy, the female elephant at Salt Lake City Zoo.
So far, Dr Hildebrandt and fellow zoologists, Frank Goeritz and Robert Hermes, have successfully created 19 successful elephant calves. They are helping to create a captive breeding programme so that zoos will not be dependent on animals captured from the wild.
But their biggest challenge is the northern white rhino where the stakes are far higher. It is the second largest land mammal and has lived on Earth for 50 million years, but is now dependent on Dr Hildebrandt's team for its survival.
Horizon: The Elephant's Guide to Sex is on Tuesday, 20 March 2007, at 2100 GMT on BBC Two.