Aug. 5 (Bloomberg) -- Almost half of all primates face extinction due to hunting and destruction of their habitats, a study of 634 species and subspecies found.

Gorillas, lemurs and orangutans are among 303 of the animals that are in danger of extinction, according to the review, carried out by the International Union for Conservation of Nature's Primate Specialist Group. Results of the study were e- mailed today by the IUCN.

``The situation is far more severe than we imagined,'' Russell Mittermeier, chairman of the primate group, said in an e- mailed statement. ``Tropical forest destruction has always been the main cause, but now it appears that hunting is just as serious a threat in some areas, even where the habitat is still quite intact. In many places, primates are quite literally being eaten to extinction.''

The latest findings will be included in October in the IUCN's Red List of endangered species. The study showed the threats to primates, the closest relatives to humans, span the globe, with species in Asia the worst-affected.

In Cambodia, 90 percent of primates may die out, and in Vietnam, Indonesia and Laos, more than 80 percent face extinction, according to the study. In Africa, 11 of 13 types of red colobus monkey are critically endangered or endangered, the two highest degrees of threat.

The 2007 Red List categorizes 39 percent of primate species as threatened with extinction. The jump to 48 percent in the list to be published in October hasn't happened in one year, because the last full assessment of all primates was carried out in 1996, according to the union.

Protecting Forests

Even as dangers rise, conservation measures can rescue species, the union said. Brazil's efforts to protect the black lion tamarin and the golden lion tamarin resulted in both species becoming less endangered in the past five years, it said.

``If you have forests, you can save primates,'' Anthony Rylands, deputy chairman of the primate group, said. ``The work with lion tamarins shows that conserving forest fragments and reforesting to create corridors that connect them is not only vital for primates, but offers the multiple benefits of maintaining healthy ecosystems and water supplies, while reducing greenhouse-gas emissions that cause climate change.''

Researchers also considered reclassifying mountain gorillas to endangered from critically endangered because their population is increasing, the union said. The category wasn't changed because of political turmoil in the Democratic Republic of Congo, Rwanda and Uganda, and the killing last year of eight mountain gorillas in their jungle habitat, the group said.

To contact the reporter on this story: Alex Morales in London at amorales2@bloomberg.net.

Last Updated: August 5, 2008 08:29 EDT