The giraffe is not one species, but four separate ones - according to the most inclusive genetic analysis that could have significant conservation implications for the world's tallest mammal. Up until now, scientists had only recognised a single species of giraffe made up of several subspecies. The unexpected findings highlight the urgent need for further study of the four genetically isolated species and for greater conservation efforts for the animal, researchers said. "We were extremely surprised, because the morphological and coat pattern differences between giraffe are limited," said Axel Janke, a geneticist at Goethe University in Germany. Giraffes are also assumed to have similar ecological requirements across their range but no one really knows, because this megafauna has been largely overlooked by science," he said. Giraffes are in dramatic decline across their range in Africa. Their numbers have dropped substantially over the last three decades, from more than 150,000 individuals to fewer than 100,000, researchers said. Despite that there has been relatively little research done on giraffes in comparison to other large animals, such as elephants, rhinoceroses, gorillas and lions, they said. About five years ago, Julian Fennessy of Giraffe Conservation Foundation in Namibia approached Janke to ask for help with genetic testing of the giraffe. Fennessy wanted to know how similar (or not) giraffes living in different parts of Africa were to each other, whether past translocations of giraffe individuals had inadvertently "mixed" different species or subspecies, and, if so, what should be done in future translocations of giraffes into parks or other protected areas. In the new study, Janke and his research group examined the DNA evidence taken from skin biopsies of 190 giraffes collected by Fennessy and team all across Africa. The extensive sampling includes populations from all nine previously recognised giraffe subspecies. The genetic analysis shows that there are four highly distinct groups of giraffe, which apparently do not mate with each other in the wild. As a result, they say, giraffes should be recognised as four distinct species. These four species include: southern giraffe, Masai giraffe, reticulated giraffe and northern giraffe, which includes the Nubian giraffe as a distinct subspecies. The discovery has significant conservation implications, the researchers said. "With now four distinct species, the conservation status of each of these can be better defined and in turn added to the International Union for Conservation of Nature and Natural Resources (IUCN) Red List," Fennessy said. The research was published in the journal Current Biology.