Only 8,000 remain of the most vulnerable chimpanzee sub-species, the Pan troglodytes vellerosus, which is found predominantly in Nigeria, and it could be extinct within two decades.
The study was presented in Johannesburg at a conference of The Pan African Sanctuaries Alliance (PASA), which cares for orphaned or injured great apes.
"It is believed that the illegal hunting and eating of apes - known as the bushmeat crisis - has had the greatest impact on the rate of decline, along with deforestation, human encroachment and disease," PASA said in a statement.
Norm Rosen, an anthropologist at California State University-Fullerton, who co- ordinated the study, said: "The situation is much more critical than we thought."
The study used the rate of orphans brought by people to sanctuaries to calculate the loss of chimpanzees in the wild. This showed a dramatic increase in the number of baby chimps losing their parents.
Dr Rosen’s study, which estimates that ten chimpanzees in the wild are killed for every orphan that reaches a sanctuary, predicts that the vellerosus subspecies will become extinct in the next 17 to 23 years.
The other three chimpanzee subspecies face slightly better odds, but all are expected to disappear in 41 to 53 years, at their current rates of decline.
"The numbers at the sanctuaries don’t lie. You don’t get the kind of steady stream of orphaned chimpanzees we’re seeing without a devastating drop in the wild population," said Dr Rosen.
Chimpanzees are found in western, central and eastern Africa. The 19 PASA sanctuaries currently care for approximately 670, a number that has risen by more than 50 per cent in the last three years.
The study is the latest to sound the alarm about the fate of the great apes, which consist of chimps, gorillas, bonobos and the orangutans of Asia.
One recent UN study said less than 10 per cent of the forest home of Africa’s great apes will be left relatively undisturbed by 2030 if road building, construction of mining camps and other infrastructure developments continue at current levels.
Nona Gandleman, the director of communications at the internationally renowned Jane Goodall Institute which has been researching chimpanzee behaviour for more than 40 years, said: "Some estimates put the time left for chimpanzees at less than 50 years, so this really is a crisis which needs to be addressed now. Chimpanzees still teach us so much about ourselves, and research still yields information that helps us understand human behaviour."