The white tiger is, in reality, a Bengal tiger that has a genetic mutation. With their white fur, brown or black stripes, and blue eyes, these tigers are not albinos, but are leucistic (their lack of pigment cells doesn’t result in total depigmentation).
The tiger has 19 pairs of chromosomes (one pair being its sex chromosomes); that is to say, it has a total of 38 chromosomes, containing all of the individual’s genes (their genotype). One of these genes, carried on a pair of chromosomes, is responsible for producing the characteristics of a “classic” coat; when this pair contains a certain mutation, it results in a “white” (leucistic) coat.
Few white tigers are born in the wild, notably because their mutation is recessive. For a white tiger to be born, both of its parents must be a carrier of this mutated gene, and have passed on this gene during reproduction. Therefore a tiger that doesn’t carry the mutated gene and a white tiger will produce “normal” cubs, which nonetheless carry the mutated gene. Two white tigers will have white cubs. Finally, a “classic” tiger that carries the mutated gene and a white tiger have a 50% chance of producing white cubs.
Whilst this big cat has distinctive characteristics, they don’t make it unwell or mean that it can’t survive. In fact, individuals that have been captured have reached adulthood, having been able to adapt to their environment. Furthermore, data from over four centuries ago describes the presence of these white-furred big cats in the forests of India. The threats facing all of the subspecies — notably trophy hunting that targets individuals with remarkable morphological characteristics — have led to the disappearance of the white tiger. The last wild tiger was seen in 1958, and was killed in the same year.
It is understood that all captive specimens have descended from one single white tiger that was captured in 1951. This explains the small size of these tigers’ gene pool, which can result in serious health problems. In order to avoid problems of inbreeding (handicaps, eye disorders…), international tiger-breeding programmes regulate births and select authorised pairs of tigers for reproduction. This also ensures the continuity of their remarkable genetic heritage, preserving it as it was already present in the natural environment.
Although the white tiger no longer exists in the wild, the Bengal tiger and five other subspecies have survived, in spite of the threats they face.