The macaques are critically endangered, according to the IUCN Red List of Threatened Species.

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Its evidence will inform the IUCN Red List of threatened and endangered species.

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One penultimate index of health, or lack thereof, is the IUCN Red List, which elucidates those many species that are vulnerable, rare and endangered throughout the world.

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This is the first time that a species which was once Extinct in the Wild has improved in status by three full categories on the IUCN Red List.

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The latest update to the IUCN Red List of Threatened Species reviews more than 60, 000 species, concluding that 25% of mammals on the list are at risk of extinction.

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If one looks at the IUCN Red List, the global authority on threatened species, the concentrations are much higher, with 83% of the most threatened birds, 82% of the most threatened mammals, and 90% of the most threatened amphibians concentrated in the Hotspots.

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The species are listed on the International Union for Conservation of Nature (IUCN) Red List - a comprehensive source of information on the status of wild species facing a high risk of global extinction - as being 'vulnerable'.

BBC: Newquay bred Owston's civets flown to Vietnam

The species, Eulemur cinereiceps, is listed as critically endangered on the International Union for Conservation of Nature (IUCN) Red List.

BBC: Linton Zoo celebrates rare white-collared lemur birth

The species, native to South Africa and Namibia, is classified as endangered on the International Union for Conservation of Nature (IUCN) Red List.

BBC: Endangered penguin chicks hand-reared at Whipsnade Zoo