An African elephant in Vienna Zoo has been impregnated using frozen sperm from a male living in the wild, in what the Zoo said Monday was a world first. Pregnancy has been achieved before elsewhere using frozen sperm in two cases, once with an African elephant and once with an Asian one, but both times the males were in captivity and the foetuses died, a zoo spokeswoman told AFP. \"If this calf is born it will be the first time worldwide that this works with frozen sperm,\" she said. \"Already this is the first successful insemination using frozen sperm from a wild male. This is something very special.\" Tonga, the 26-year-old elephant, is nine months into her 22-month pregnancy. The sperm came from a wild bull elephant in South Africa. Using sperm from wild elephants is seen as particularly important in order to widen the narrowing gene pool of elephants living in zoos and animal parks around the world caused by a shortage of suitable bulls living in captivity. More information including ultrasound images is due to be presented at a news conference on Tuesday. Artificial insemination using sperm that is frozen and then thawed has worked in other mammals, including rhinos, but with elephants, an endangered species, it has proven problematic. Tiergarten Schoenbrunn or Vienna Zoo, the world\'s oldest, teamed up with the Leibniz Institute for Zoo and Wildlife Research in Germany, Zooparc de Beauval in France and Pittsburgh Zoo in the United States for the project.