She knows more than 2,000 words, has friends in high places and loves cats and old films. But in her 40th year, Koko the 'talking' gorilla seeks a new challenge - a baby. Koko ... was taught American sign language when she was about a year old. Now 40, she apparently has a working vocabulary of more than 1,000 signs and understands around 2,000 words of spoken English. Forty years on, the Gorilla Foundation's Koko project has become the longest continuous inter-species communications programme of its kind anywhere in the world. Over the years Koko has inadvertently become a poster child for the gorilla conservation movement. There are several subspecies of gorilla, and today, according to the International Union for Conservation of Nature, all are either endangered or critically endangered. There are thought to be more than 700 mountain gorillas left in the wild; just under 17,000 eastern lowland gorillas, 10,000 western lowland gorillas, and only 200-or-so Cross River gorillas. All are in sub-Saharan Africa and are threatened by either the illegal trade in bushmeat, loss of habitat due to logging and agricultural expansion, or disease. Some conservationists believe stories like Koko's ... could be the answer.