The Asian small-clawed otter (Aonyx cinereus), also known as the oriental small-clawed otter and the small-clawed otter, is an otter species native to South and Southeast Asia. It has short claws that do not extend beyond the pads of its webbed digits. With a total body length of , it is the smallest otter species in the world. The Asian small-clawed otter lives in riverine habitats, freshwater wetlands and mangrove swamps. It feeds on molluscs, crabs and other small aquatic animals. It lives in pairs, but was also observed in family groups with up to 12 individuals. It is listed as Vulnerable on the IUCN Red List, and is threatened by habitat loss, pollution, and in some areas also by hunting. Taxonomy Lutra cinerea was the scientific name proposed by Johann Karl Wilhelm Illiger in 1815 for an otter collected in Batavia. In the 19th and 20th centuries, several zoological specimens were described: Lutra concolor proposed by Constantine Samuel Rafinesque in 1832 was a uniform coloured otter from Assam. Rafinesque also proposed Amblonyx as name for a subgenus for otters with short, obtuse claws. Lutra leptonyx proposed by Thomas Horsfield in 1824 were two adult small-clawed otters collected in Java. It was subordinated to the genus Aonyx by John Edward Gray in 1843. Amblonyx cinerea nirnai proposed by Reginald Innes Pocock in 1940 was a dark brown small-clawed otter from Virajpet in South India. Phylogeny Results of a mitochondrial cytochrome B analysis published in 1998 indicated that it should be subordinated to the genus Aonyx. Results of a molecular study published in 2008 showed that the Asian small-clawed otter is a sister taxon of Lutrogale, lending support to retaining the genus Amblonyx or expanding Aonyx to make it monophyletic. They genetically diverged about . The Asian small-clawed otter groups with the African clawless otter (Aonyx capensis) and the smooth-coated otter (Lutrogale perspicillata) into a sister clade with the genus Lutra. Hybridisation of Asian small-clawed otter females with smooth-coated otter males occurred in Singapore. The resulting offspring and their descendants bred back into the smooth-coated otter population, but maintained the genes of their small-clawed otter ancestors. Today, a population of at least 60 hybrid otters are present in Singapore. Characteristics The Asian small-clawed otter has deep brown fur with some rufous tinge on the back, but paler below. Its underfur is lighter near the base. The sides of the neck and