According to the Save the Tiger Fund, there are ~5,000 tigers in the wild. There are certainly not 4,000 white tigers in the wild, as this article says, and, of course, the white tiger is not an "endangered species".
(Tunisia) - Like all other rare and endangered non-domesticated animals, baby White Tigers require extremely species-specific nutrition and care. They, require feeding every 2 hours, 24 hours a day for the first 3 weeks of their life.
The mother of these tiger cubs in El-Mahdia, Tunisia refuses to feed them or doesn't have enough milk. Local veterinary authorities came up with the idea of entrusting a dog with the delicate mission. Leaving only one cub to its mother, two cubs were introduced to a local dog. The dog responded and soon took the cubs as her own.
The Bengal Tiger or Royal Bengal Tiger (Panthera tigris tigris) is a subspecies of tiger primarily found in Bangladesh and India and also in Nepal, Bhutan, Myanmar and in the south of Tibet. It is the most common tiger subspecies, and lives in a variety of habitats, including grasslands, subtropical and tropical rainforests, scrub forests, wet and dry deciduous forests and mangroves. Its fur is orange-brown with black stripes, although there is a mutation that sometimes produces white tigers. It is the national animal of both Bangladesh and India.
There are only 4000 white tigers in their natural habitat and 200 in captivity.