Los Angeles - So how exactly do you save an almost extinct rhinoceros? Turns out, a test tube baby rhino could be the solution, being sought by experts on three continents. But it won't be easy.Keepers at California's world-renowned San Diego Zoo announced this week that Angalifu, one of its two northern white rhinos, had died at the ripe old age of 44.That leaves only five other members of the species in the world: one female in California, one in the Czech Republic, and two females and one male - the sole remaining on the planet - in Kenya.The trouble is, four of the five are already on their last legs - being already into their 40s, for a species with an average age of 43. Only one, a female in Kenya, is still young, having been born in 2000."It is seriously going to be an uphill battle. There is absolutely no doubt about that," Randy Rieches, curator of mammals for the San Diego Zoo Safari Park, told AFP."We're looking at a bunch of different options," he said, which includes in vitro fertilization and artificial insemination, while admitting they were "grasping at straws at this point in time”.The real problem, he said, is in Africa, where rhinos have been hunted for decades. The northern white rhino has been nearly wiped out by poaching for their horns, and by wars, according to the World Wildlife Foundation.Ten years ago there were known to be some 30 animals living wild in the Garamba National Park in the Democratic Republic of the Congo.Aware that they were threatened, conservationists organized for a handful of them to be transported to Kenya - but in the end the DRC authorities blocked the move, saying the animals should be kept in the country."That proved to be a very poor decision, because they weren't able to protect them because of the remoteness of the park”, said Rieches, who has worked with rhinos for over three decades.Poacher problemThe poachers took swift advantage of the decision. "There were gangs coming through at that point in time from several different countries," he said.He added: "Now it has become so horrific with rhino poaching because rhino horn prices [have] gone through the roof. They're doing it now with gunships. The rangers on the ground are so severely outmatched. It's just almost impossible."They are literally putting their lives on the line to try to stop the rhino poaching," he said.Coming back to the current conundrum, he said it was important that the three places with surviving rhinos - San Diego, the Czech Republic's Dvur Kralove Zoo, and Kenya's Ol Pejeta Conservancy - work together.A Czech expert visited the California facility a month ago, while a German expert was recently in Kenya to retrieve semen samples."We're actually in partnership with everyone that still has animals," said the US expert. "So everyone is trying methods on their own, but working together with samples."Specifically, they have frozen samples of semen. The idea would be either to try to fertilize eggs in the laboratory - the test tube rhino scenario - or alternatively to impregnate a southern white rhino, of which there are far more.You would then take female calves from that combination, and combine them with sperm from another northern white. But the best you could hope for would be a 15/16 pure northern white, Rieches said.Long-term projectIn any case, he is not expecting a breakthrough overnight. The gestation period for a northern white rhino is 17 months."So this is a long term project. We're in it for the long haul... it will take time before something comes to fruition, it certainly will be a couple of years," he said.For Rieches, the quest is personal. He has worked for the conservancy group San Diego Zoo Global for 36 years, and is on the board of directors of the International Rhino Foundation.If the last northern white rhino dies, he will be devastated."A large portion of my life has been rhinos... it's going to be a huge, huge thing for me if this happened on my watch, if this happened during my lifetime."