About White Tigers
White tigers are white with black stripes. generally the black stripes are normal, but in some cases they are indistinct. They are a color variant of the Bengal tiger (Panthera tigris tigris). The loss of red and yellow coloring is due to an autosomal recessive trait.
Chinchilla, color dilute, leucistic.
In the Wild
Some sources claim that white tigers never occurred in the wild, and while they were always clearly very rare, this is not the case. White tigers were reported occasionally in the wild in India from the 1500s until the last known example in 1958.
The Maharaja of Rewa (in India) was known to have owned a white tiger captured in the wild as a cub. The tiger, called Mohan, lived from 1951 until 1970. there are ongoing efforts to conserve a line of white tigers in Rewa.
All of the white Bengal tigers in existence now are in captivity. Some breeders select for this trait and maintain it by inbreeding. However if tigers were genetically analyzed it might be possible to perpetuate the trait without excessive inbreeding. The question is, should we be breeding exotic, naturally wild animals for purely cosmetic traits at all?
Breeding for cosmetic traits is counter to the usual conservation goals that justify the keeping of wild animals is zoos. to except this practice in tiger would be to suggest they are now domesticated animals that we can use for decorative and entertainment purposes without consideration for the preservation of the species in the wild.
While distasteful this approach may not be so unreasonable now that only around 4000 tigers live in the wild and 20,000 or more are kept in captivity (around 200 of the white). there is a case to be made for accepting that the tiger is now at least partially a domestic species. And white tiger cubs can mean great publicity (e.g. Tobu Zoo, Japan 2015). White Tiger exhibits are pr of many zoos including New Delhi Zoo in India.
On the other hand most American zoos and many other zoos and refuges around the world prohibit deliberately breeding for white tigers. They are still fully commit to the preservation fo the species in the wild and as a wild type in captivity.
White white coloration is part of the tigers natural range, it can also be considered a defect. The inbreeding associated with maintaining white coloration is probably the cause of many of problems associated with this coloring.
However lack of pigmentation can also have direct effect on various parts of the animal including defects in vision that sometimes lead to them being cross-eyed. This kind of defect is common in reduced-pigments variants of many different animal species--suggesting that full pigmentation is adaptive and "normal" for these animals.
However some researchers (e.g. Xu et al, 2013) assert that the abnormalities in white tigers are purely due to inbreeding, and not the mutation itself.
In 2013 the genetic cause of white tigers was identified. The variant is causes by a single gene related to pigmentation in many animals that is identified as SLC45A2. this recessive gene must be present in both parents and suppresses the production of red and yellow pigments.
The white tiger gene is similar to autosomal recessive genes that are referred to as "chinchilla" in other animal species.
White Tigers in the News
Because white tigers are high profile animals their deaths in zoos are often reported in the news. For example a newly acquired tiger at the Jaipur zoo in India that died within weeks of arrival of an infection (2013). And four tigers that died within a two week period that the Arignar Anna Zoological Park (India, 2013).
White tigers are also as dangerous of any other tiger. In 2016 a tiger in the "White Tiger Show" attacked a trainer leading to her hospitalization.
The white tiger symbolizes one of the four main constellations as represented in China.
Should zoos and parks deliberately breed for the white trait?
It seems part of human nature to see unusual or extreme traits as interesting and beautiful. And any animal, once born, should be respected. But there is ample evidence that reduced pigment is associated with deficits in health and well being, and so it should not be actively selected for in captive tiger populations.
- Bernays, M. E., & Smith, R. (1999). Convergent strabismus in a white Bengal tiger. Australian Veterinary Journal, 77(3), 152-155.
- Guillery, R. W., & Kaas, J. H. (1973). Genetic abnormality of the visual pathways in a" white" tiger. Science, 180(4092), 1287-1289.
- Pazzi, P., Lim, C. K., & Steyl, J. (2014). Tetralogy of Fallot and atrial septal defect in a white Bengal Tiger cub (Panthera tigris tigris). Acta Veterinaria Scandinavica, 56(1), 12.
- Robinson, R. (1969). The white tigers of Rewa and gene homology in the Felidae. Genetica, 40(1), 198-200.
- Thornton, I. W. B. (1978). White tiger genetics–further evidence. Journal of Zoology, 185(3), 389-394.
- Xu, X., Dong, G. X., Hu, X. S., Miao, L., Zhang, X. L., Zhang, D. L., ... & Luo, S. J. (2013). The Genetic Basis of White Tigers. Current Biology.