have ever existed reaching weights of more than . The tigers of the Sunda islands are smaller and less heavy than tigers in mainland Asia, rarely exceeding in weight. Colour variations There are three other colour variants – white, golden and nearly stripeless snow white – that are now virtually non-existent in the wild due to the reduction of wild tiger populations, but continue in captive populations. The white tiger has white fur and sepia-brown stripes. The golden tiger has a pale golden pelage with a blond tone and reddish-brown stripes. The snow white tiger is a morph with extremely faint stripes and a pale reddish-brown ringed tail. Both snow white and golden tigers are homozygous for CORIN gene mutations. The white tiger lacks pheomelanin (which creates the orange colour), and has dark sepia-brown stripes and blue eyes. This altered pigmentation is caused by a mutant gene that is inherited as an autosomal recessive trait, which is determined by a white locus. It is not an albino, as the dark pigments are scarcely affected. The mutation changes a single amino acid in the transporter protein SLC45A2. Both parents need to have the allele for whiteness to have white cubs. Between the early and mid 20th century, white tigers were recorded and shot in the Indian states of Odisha, Bihar, Assam and in the area of Rewa, Madhya Pradesh. The local maharaja started breeding tigers in the early 1950s and kept a white male tiger together with its normal-coloured daughter; they had white cubs. To preserve this recessive trait, only a few white individuals were used in captive breeding, which led to a high degree of inbreeding. Inbreeding depression is the main reason for many health problems of captive white tigers, including strabismus, stillbirth, deformities and premature death. Other physical defects include cleft palate and scoliosis. The Tiger Species Survival Plan has condemned the breeding of white tigers, alleging they are of mixed ancestry and of unknown lineage. The genes responsible for white colouration are represented by 0.001% of the population. The disproportionate growth in numbers of white tigers points to inbreeding among homozygous recessive individuals. This would lead to inbreeding depression and loss of genetic variability. There are also records of pseudo-melanic or black tigers which have thick stripes that merge. In Simlipal National Park, 37% of the tiger population has this condition, which has been linked to isolation and