Rhinoceros horn—the natural, but politically incorrect version of viagra—can now be protected from poachers using DNA technology. Scientists at the National Institute of Immunology in India (NII; New Delhi) have just completed six months of tests on a DNA detection device that has not only been shown to detect rhino horn but also to tell whether the specimen comes from India or elsewhere. "It will be a valuable weapon in the hands of conservationists wanting to track down the source of rhino horn in the illegal market," says Sher Ali, head of NII's molecular genetics laboratory. Ali and his colleagues have discovered a repetitive 906 base pair DNA sequence that is unique to India's one-horned rhinoceros (Rhinoceros unicornis). The sequence is not present in the closely related African double-horned black rhinoceros (Diceros bicornis) or any other species of rhino. "This distinguishing feature will help identify if a particular horn came from India or Africa," says Ali. The great Indian one-horned rhino is an endangered species—currently numbering about 2000—and is confined to three or four protected forests in Assam and West Bengal in eastern India.