The Sumatran tiger is a population of Panthera tigris sondaica on the Indonesian island of Sumatra. It is the only surviving tiger population in the Sunda Islands, where the Bali and Javan tigers are extinct. Sequences from complete mitochondrial genes of 34 tigers support the hypothesis that Sumatran tigers are diagnostically distinct from mainland subspecies. In 2017, the Cat Classification Task Force of the Cat Specialist Group revised felid taxonomy and recognizes the living and extinct tiger populations in Indonesia as P. t. sondaica. Taxonomy Felis tigris sondaicus was the scientific name proposed by Coenraad Jacob Temminck in 1844 for a tiger specimen from Java. Panthera tigris sumatrae was proposed by Reginald Innes Pocock in 1929, who described a skin and a skull of a tiger zoological specimen from Sumatra. The skull and pelage pattern of tiger specimens from Java and Sumatra do not differ significantly. P. t. sondaica is therefore considered the valid name for the living and extinct tiger populations in Indonesia. Evolution Analysis of DNA is consistent with the hypothesis that Sumatran tigers became isolated from other tiger populations after a rise in sea level that occurred at the Pleistocene to Holocene border about 12,000–6,000 years ago. In agreement with this evolutionary history, the Sumatran tiger is genetically isolated from all living mainland tigers, which form a distinct group closely related to each other. The isolation of the Sumatran tiger from mainland tiger populations is supported by multiple unique characters, including two diagnostic mitochondrial DNA nucleotide sites, ten mitochondrial DNA haplotypes and 11 out of 108 unique microsatellite alleles. The relatively high genetic variability and the phylogenetic distinctiveness of the Sumatran tiger indicates that the gene flow between island and mainland populations was highly restricted. Characteristics The Sumatran tiger was described based on two zoological specimens that differed in skull size and striping pattern from Bengal and Javan tiger specimens. It is darker in fur colour and has broader stripes than the Javan tiger. Stripes tend to dissolve into spots near their ends, and on the back, flanks and hind legs are lines of small, dark spots between the regular stripes. The frequency of stripes is higher than in other subspecies. Males have a prominent ruff, which is especially marked in the Sumatran tiger. The Sumatran tiger is one of the smallest tigers. Males measure between the pegs in head-to-body length, with the greatest skull length of