11 Endangered Primates on the Brink of Extinction

Like its lemur cousins, the silky sifaka is restricted entirely to the island of Madagascar. The name sifaka is an imitation of their alarm call, which should be resounding frequently, since fewer than 1,000 are thought to exist in the wilds of northeastern Madagascar. A chaste species, they mate just one day a year and eat a wholly vegetarian diet; young ride clinging to their mother's stomach or back for weeks after birth.

Read more about Madagascar:
> Madagascar Tortoise Crisis (PHOTOS)
> Madagascar Featured at the Bronx Zoo

This nocturnal tree-nesting lemur is so rarely seen in the isolated dry forests of northern Madagascar that scientists believe as few as 100 remain alive, though total population estimates are not available. Local villagers cut their forest habitat for charcoal, and also hunt them for meat.

Read more about Madagascar:
> Madagascar Tortoise Crisis (PHOTOS)
> Madagascar Featured at the Bronx Zoo

Occupying habitat only the size of midtown Manhattan on Siau Island, its extremely small home range is a huge threat. That locals eat them as snacks does not help, and though this species was only recently described by science, it's thought that at most a few thousand live in the wild.

The locals have a much more elegant name for this species, the simakobu, which is one of four endangered primate species living in the Pagai Islands, off the west coast of Sumatra. There are believed to be fewer than 3,500 simakobus, fewer than 1,050 Kloss's gibbons, fewer than 1,600 leaf monkeys, and fewer than 8,000 pig-tailed macaques on the Pagai Islands. While some habitat is protected in the Siberut National Park, much of the native forest is being lost to logging, particularly as the forest is replaced with palm oil plantations, and other development.

Hoolock gibbon populations in India, Bangldesh and Myanmar have declined 80% in a generation, and now stand at just 5,000 individuals, with many so scattered in forest fragments that they could be doomed. It is one of two critically endangered gibbons on the list (the other is the Eastern black-crested gibbon living along the border of China and Vietnam, with about 110 alive today).

Native to the forests of Northwestern Colombia, and loss of forests is the main reason they are considered critically endangered. Every two years, Colombia loses enough forest enough to cover Rhode Island, according to the United Nations, and even so-called protected areas are subject to intense illegal logging; three parks with cotton-top tamarin habitat have lost 42% to 70% of their forests since being designated protected areas, according to the IUCN, the U.N. organization responsible for protecting wildlife. For the cotton-top tamarin, clearing forests for palm oil plantations, and the swamping of forests for hydroelectric power along the Pacific Coast represent big threats. (Deforestation threatens much more than the cotton-top tamarin, as Colombia is one of the most biologically diverse nations on Earth.) For years, they were also captured for medical research; as many as 40,000 were exported to U.S. labs – a number that seems even more shocking when you consider that only an estimated 6,000 remain in the wild today.

To help, as consumers, you can choose products that were not tested on animals, and do not contain palm oil.

Read more about Colombia
> 10 New Species of Amphibians Discovered in Colombia (PHOTOS)

Also known as the blue-eyed black lemur, Sclater's black lemur is so rarely seen that it was "rediscovered" in 1983 after a century without a sighting. It inhabits a portion of Madagascar roughly the size of Rhode Island and there are thought to be fewer than 7,000 alive today, after suffering an 80% decline in population over 25 years. Deforestation and hunting are the major threats to its existence. The Mullhouse Zoo in France has a captive breeding program for the species.

Read more about Madagascar:
> Madagascar Tortoise Crisis (PHOTOS)
> Madagascar Featured at the Bronx Zoo

Constrained to isolated forests in an area not much bigger than New York City in southeastern Madagascar, gray-headed lemurs number no more than 9,500 – few enough that scientists worry about its ability to maintain a healthy genetic diversity. A vegetarian, the gray-headed lemur is particularly fond of flowers. Hunting and deforestation are the biggest threats, but strong cyclones have also swept through, killing many.

Read more about Madagascar:
> Madagascar Tortoise Crisis (PHOTOS)
> Madagascar Featured at the Bronx Zoo

The two subspecies of the variegated spider monkey (also known as the brown spider monkey) are both critically endangered and inhabit small areas of Colombia and Venezuela, where deforestation and hunting (for food and for pets) are major threats. Population estimates are not available.

Read more about Colombia
> 10 New Species of Amphibians Discovered in Colombia (PHOTOS)

Isolated to cloud forests in the tropical Andes of Peru, the yellow-tailed woolly monkey is so little-studied that scientists haven't estimated its population. But as its numbers dwindle in the face of hunting for its meat and fur (it's trusting nature has not served it well), and deforestation of its cloud forest, researchers believe it is in imminent danger of extinction.

Read more about Peru
> 4 New Species Discovered in Peru
> The World's Most Bizarre (and Wonderful) Hummingbird (VIDEO)