Scientists in Nigeria are warning that twelve species of monkeys are threatened with extinction because they're gradually being deprived of their natural surroundings.

One of Nigeria's leading environmental experts, Adegoke Adegoroye, told a conference in Lagos this was due to over-logging and hunting.

Mr Adegoroye said the endangered animals included the rare drill monkey and the white-throated monkey, which is found only in Nigeria.

He said the authorities were not doing enough to safeguard the country's environment, and that several other animals had already died out in Nigeria, such as the pygmy hippopotamus, the giraffe and the black rhinoceros.