In this photo taken on 13 March 2012, an African rhinoceros is seen at a private zoo of Bao Son Paradise Park in Hanoi, Vietnam, which has 24-hour security to protect against potential poachers. Wildlife conservationists warn that Vietnam's surging demand for rhino horn, which is believed to treat everything from hangovers to cancer, is threatening to wipe out the world's remaining rhino populations. Illegal killings in Africa hit a record high in 2011 and are expected to worsen this year. (AP Photo/Na Son Nguyen)