Scientists are investigating a horrific new venereal disease which is affecting baboons in Tanzania.
This is not the first venereal disease to hit baboons
The disease first appeared about a month ago and has infected an estimated 200 animals, reports the New Scientist magazine.
Male baboons are particularly badly hit by the new disease, says Elibariki Mtui from the African Wildlife Foundation in Arusha.
"The genitals kind of rot away, then they just drop off," he said.
Some of the infected males have died.
So far, the disease has only been found in the Lake Manyara National Park but there are fears that it could spread.
Male baboons move between different troops and so sexually transmitted diseases could spread quickly.
However, Dee Carey, from the Southwest National Primate Research Centre in San Antonio, Texas, US, says that with so little information on the disease, it is difficult to evaluate the risks.
Scientists from the Tanzania Wildlife Research Institute have gone to Lake Manyara to take samples from infected baboons and identify the new disease.
They are working with the Institute of Primate Research from neighbouring Kenya.
This is not the first case of venereal diseases in baboons, Dr Carey says.
He suggests that the deaths may have been caused by subsequent infections, rather than the new disease.