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.

Sumatran orangutan
Sumatran orangutans are critically endangered. Their habitats have been destroyed by logging and palm-oil plantations. Reuters
Philippine tarsier
The Philippine tarsier is under threat as it is heavily harvested as food and sold for the pet trade IStock
golden snub nosed monkey
The golden snub nosed monkey, found in the forests of central and southwest China, is endangered because of habitat loss IStock
Roloway monkey
The Roloway monkey, which was once found in Guinea, Ghana and Ivory Coast, is now nearly extinct IStock
Kashmir grey langur
Kashmir grey langurs are endangered, largely because of human agricultural practices and development IStock
Javan slow loris
Populations of the Javan slow loris are under threat because of the illegal exotic pet trade IStock
colombian brown spider monkey
The Colombian brown spider monkey is critically threatened because of deforestation and unsustainable logging practices IStock
Red ruffed lemur
The red ruffed lemur, native to Madagascar, is critically threatened because of the pet trade, burning of land and hunting IStock
Eastern lowland gorilla
A subspecies of eastern gorilla, the eastern lowland gorilla is found only in the rainforests of eastern Democratic Republic of the Congo IStock
Red colobus monkey
All species of red colobuses - except the Central African red colobus - are assessed by the IUCN as endangered or critically endangered IStock