A new report has found that 60 per cent of all primates are now at risk of extinction.
The research, which assessed the conservation status of 504 species of nonhuman primates, found that three quarters of the world's primate species are undergoing an "alarming" population decline.
Dr Alejandro Estrada, a senior research scientist at the Institute of Biology, National Autonomous University of Mexico, said:
It was surprising to learn that the rate of decline was so high.
This is of great concern as the figures suggest that we may be reaching a tipping point -- or perhaps we are already there.
The study found that all of the current threats to primates were driven by human activity.
The destruction of habitat extinguishes resources such as shelter, food and water, divides social groups, and also leaves primates open to the risk of predation and contamination from pathogens.