One Slight Genetic Tweak Gave White Tigers Their Pale Coats

A single change in a pigment gene is responsible for white tigers’ famous snowy coats, LiveScience reports. Zookeepers have inbred captive white tigers for decades in order to preserve their unique coat, but until now scientists did not know the genetic basis of the felines’ striking white fur.

The researchers mapped 16 related tiger genomes, which included animals with both white and orange fur. They found that one gene, called SLC45A2, turned up in a slightly altered version in the white tigers. It acts to inhibit yellow and red coloring but doesn’t impact black. That same gene change also affects some fish, chickens, horses and even European humans. The mutation itself does not appear to be detrimental to the animals’ health, the BBC reports.

A number of the white tigers found in zoos have health issues, such as eyesight problems and some deformities.

However, Luo and colleagues say these deficiencies are a consequence of inbreeding by humans and that the white coats are in no way indicative of a more general weakness in the Bengal variant.

Though white tigers populate zoos around the world and are often one of their most crowd-pleasing attractions, the animals are rarer than those displays let on. In fact, researchers think white tigers are now extinct in the wild. LiveScience elaborates: 

Records of white tigers in India date back to the 1500s, Luo and colleagues say. They appear able to survive in the wild, as their primary prey, such as deer, are probably colorblind. The animals were widely hunted, and the last known free-ranging white tiger was shot in 1958. Habitat destruction probably contributed to the cats’ decline.

More from Smithsonian.com:

The Fight to Save the Tiger 
Tiger Tracks 

Rachel Nuwer | | READ MORE

Rachel Nuwer is a freelance science writer based in Brooklyn.