Earth is dominated by primates, mainly due to the 7.4 billion humans who live on this planet. However there are hundreds of other primate species and subspecies, many of which are in danger of becoming extinct because of poaching, habitat destruction and the illegal wildlife trade. From the Sumatran orangutan to the Javan slow loris, our closest living relatives are gradually dying out.

Today (1 September) marks International Primate Day, dedicated to the preservation and protection of the animals. It was founded in 2005 by Animal Defenders International (ADI) and is held annually. The day is used by campaigners globally to highlight the many threats to primates.

As of 2014, non-human primates were not protected in law by the United Nations Universal Declaration of Human Rights and by all governments to varying degrees, meaning their interests have no formal recognition of protection. According to ADI, in the US alone over 70,000 monkeys are experimented on each year, while over 2,000 undergo testing in the UK. With the exception of Air France, all major passenger airlines have ceased their involvement in transporting the animals for testing.

Here are ten of the most endangered species of primate, to mark this most important of animal-themed days.