White tigers

White tigers are not extinct because they are not a subspecies of tiger.
Charles Darwin discovered that nature has a "nature selection". And Mendel discovered that there are some features that predominate over the others (recessive) and pass to the next generation. For example: a female white tiger crosses an orange tiger and they have 3 orange cubs. And when these 3 cubs grow-up and have 3 cubs each, this next generation of 9 animals is likely to consist of 8 orange and one white cub.
Everybody loves white tigers, they act on stages but they are not healthy. The healthy tigers are supposed to be orange and black. The white ones can have problems like not seeing things well and they don't have camouflage that a normal tiger must have. It wouldn't live in the wild it would give to much attention to it's meal. And when they are cubs they are easy targets for predators such as leopards, wild dogs and bears.

For more information check out this video: