Just five northern white rhinoceroses remain on the entire planet after a male died in a United States zoo. Angalifu, who was about 44 years old and being treated for age-related conditions, died at the San Diego Zoo Safari Park. The only known remaining northern white rhinos are an elderly female still at the Safari Park, one at a zoo in the Czech Republic and three in Africa. "Angalifu's death is a tremendous loss to all of us," said Randy Rieches, curator of mammals for the zoo. "Not only because he was well beloved here at the Park but also because his death brings this wonderful species one step closer to extinction." Northern white rhinos have been nearly eliminated because of severe poaching in Africa. None of those remaining are reproductive. Rieches said there were only about 30,000 rhinos of all types left in the world, with one of the majestic creatures killed by poachers every eight hours. Semen and testicular tissue from the male northern white rhino have been stored in San Diego with the hope new reproductive technologies will one day allow recovery. It is possible semen from northern white rhinos could be used to impregnate southern white rhinos, to eventually produce an almost pure northern white variety. But Rieches said there were various difficulties to overcome, including the complex problem of artificial insemination.