The white tigers are a genetic variant, product of the mutation of a transporter protein, of the species Panthera tigris. This white variant has amazed mankind since its discovery centuries ago in populations located in the Indian subcontinent.
Specifically, the variant occurs only in populations of the subspecies Panthera tigris tigris, also known as the Bengal tiger. Although some specimens of the subspecies have been noted Panthera tigris altaica (Siberian tiger) that are probably the result of crosses between the two subspecies, mediated by man.
At present, all known white specimens and other known coloration variations of this subspecies are only known in captive animals, as their wild counterparts have disappeared or current records in the wild are not known..
In nature there are few sightings that occur, as they are quite elusive animals due to how disadvantaged they are with respect to their camouflage in contrast to those individuals that have a typical orange coloration.
The oldest sightings date from the year 1500 in the populations of Panthera tigris present in India. Most of the populations of Panthera tigris tigris in the Indian subcontinent they are severely fragmented.
The last specimen known in nature was hunted in 1958 and it is unknown if there are still wild populations with the genetic characteristics that allow the birth of tigers with this mutation..
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White tigers are characterized by the absence of the typical orange color of Bengal tigers. Like the orange tigers, the black spots and stripes remain unaltered unlike other coloration variants such as the completely white tiger or the golden tiger.
The white tiger was long thought to be albino, however, although pheomelanin (responsible for the reddish or yellow coloration) is largely absent, eumelanin is still present in stingrays' fur and eyes..
Some white specimens may also present some degree of strabismus due to the decrease of the pigment in the epithelium of the retina and the iris during the development of the eye. In addition, white tigers are usually slightly larger than tigers of typical coloration..
The stripes on the body are usually dark brown or sepia-colored, the eyes are blue and the nose is pink along with the pads of the feet..
The white coat of the tiger is an autosomal recessive trait determined by a white locus (W) whose genotype is (w / w). The genetic basis of the heritability of the coat remains even with very little data.
Recent research indicates that the white variety, although atypical, is viable in nature because this mutation is not accompanied by any significant physiological abnormality that affects the survival of tigers in the wild..
The mutation in the transporter protein SLC45A2 due to a simple change in the amino acid sequence (A477V) is the cause of the acquisition of said coloration in the coat..
Three-dimensional homology models suggest that this change in the amino acid sequence of the protein may partially block the transporter channel, which may affect melanogenesis..
So far, other genes that determine the color of mammals have also been evaluated, both in white tigers and in those with typical coloration. The MC1R, ASIP, TYR (albino gene), TYRP1 and SLC7A11 genes were evaluated without observing variations associated with the coloration of the white tiger..
Mutation in the SLC45A2 gene affects only pheomelanin pigmentation in the tiger.
The species Panthera tigris It is in "danger of extinction" (EN) according to the international union for the conservation of nature. Of the nine subspecies that existed, three are now officially extinct.
Populations of the subspecies Panthera tigris tigris have decreased rapidly due to illegal hunting, the disappearance and destruction of their habitats, as well as the decrease in the populations of the prey that consume.
Currently the Bengal tigers have little more than 1 million kmtwo to inhabit. Their populations have decreased by more than 40% in the last two decades and it is expected that in the next three generations of tigers (approximately 21 years) the population trend will continue to decrease..
Many tiger populations are found outside of protected areas, making them more susceptible and fragile. Another of the criteria used to categorize tigers in danger of extinction is the decrease in the number of mature individuals, estimating between 2000 and 3000 reproductive adults in the wild..
Although many places with the presence of tigers are known, there is little evidence that they constitute stable reproductive populations.
The totality of individuals of white tigers that exist today are in captivity and are highly inbred in order to "preserve the recessive coloration trait". However, this brings with it a series of diseases such as premature death, the unviability of the litters and the appearance of deformities and frequent occurrence of tumors..
This set of diseases has led to speculation that the white variant of the tiger is nothing more than a genetic abnormality or deformity. However, the death of several white tigers in the wild as a result of poaching shows that the coloration does not greatly affect the survival of the individuals..
The last specimen of white tiger in the wild was hunted in 1958. There are no recent records of this coloration variant in India and the frequency of the recessive gene that causes the appearance of this phenotype in the wild is not known..
Probably the pressures that this variant suffered in the past were the same that currently exist for normal individuals: uncontrolled hunting, intervention of habitats and their fragmentation.
Panthera tigris it is a species with a wide distribution. Originally they extended from Turkey in the west, to the eastern coast of Russia. However, in the last century they have disappeared from much of central Asia, some Indonesian islands, and large areas of Southwest and East Asia..
Recently they only occupy 6% of their original territory. Breeding populations exist only in Bangladesh, Bhutan, India, Indonesia, Malaysia, Nepal, Russia, and Thailand. There are also poor and unconfirmed reproductive data in China, Myanmar and North Korea..
Panthera tigris it currently has six subspecies distinguished on the basis of molecular markers. Three other subspecies previously established based on taxonomic characteristics are extinct.
Much of the areas where tigers are found suffer anthropic pressure due to land use and poaching.
White tigers originate when the specimens that reproduce are carriers of the recessive gene (w) are heterozygous or homozygous. These tigers are highly sought after in zoos and exotic animal exhibits.
Due to this, and the non-existence of this variety in nature, a large part of the specimens that are known today are the product of inbreeding..
The reproductive characteristics are similar to that of tigers in the wild. In general they can reproduce throughout the year. The minimum age for reproduction in females is around four years and in males up to 5 years. Litters can vary between 2 and 4 puppies.
Puppies have a high mortality rate, (up to 50%), however, life expectancy increases as puppies grow older. High cub mortality rates, often attributed to human activities, pose a great risk to conservation activities in most tiger ranges..
Similarly, in the case of the white tiger, the mortality of litters resulting from inbreeding puts the conservation of the variety at risk..
These cats are clearly carnivores. In their range they feed on buffaloes, impalas, wild boars and wild pigs, primates such as langurs and deer. They can even consume other predators such as the sloth bear but to a lesser extent and juvenile elephants..
Tigers prefer to consume large prey with an average weight of between 100 and 114 kilograms. Tigers generally choose and defend territories with a high availability of prey up to 100 animals per kmtwo. Knowing this, those areas with high availability of dams are strategic points for conservation.
On the other hand, when food is scarce they can consume a wide variety of small prey such as amphibians, small rodents and rabbits. Because the dams present variations in their populations in the areas of distribution of Panthera tigris, the frequency and hunting preference of one prey or another depends on its local abundance.
In areas close to human settlements, they frequently feed on farm animals, constituting up to 10% of their diet. However, the latter results in the selective hunting of "harmful" tigers..
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