In the wild, the tiger's fur is very classic - orange stripes. This kind of fur is very beneficial to tigers. They are ambush hunters, and this "dress" is a very good camouflage color. However, in captivity, the fur colors of tigers have become very diverse. Here are the fur colors of 6 species of captive tigers:
The most unique and popular of them all is the first white-furred tiger on the right.
White tigers, many people may subconsciously think that this is an ordinary animal albino, but if you look carefully at the characteristics of a white tiger, you will find that it is different from the albino of other animals.
White tigers have black stripes on their bodies, which means they do not lack melanin like albinism. In addition, white tigers' eyes are blue, and they are not red like albinism.
In short, the white tigers we see in the zoo are not ordinary albino.
What’s even more interesting is that most of the white tigers in the zoo arebengal tiger,And they are basically the descendants of a male white Bengal tiger that was captured a long time ago.
So, the interesting question is, what are these unique white tigers all about?
First of all, white tigers do exist in the wild, and there are records of white tigers around the world since ancient times.
These tigers are different, so they are often very powerful in legends. For example, the Chinese regard the white tiger as one of the four spirits, while in Indian mythology, the white tiger is regarded as the mount of the god of war or guardian spirit.
However, white tigers are very rare in the wild, and there are even fewer records of white tiger captures. It is believed that the first white tiger was captured in India in 1915. The specific subspecies of this tiger is unknown today.
However, in 1951, King Rewa of IndiaMartand SinghAnother male white tiger has been captured in the Mukundpur forest in Siddi district.bengal tiger(There are two subspecies of tigers living in India, and one is the Indochinese tiger).
△ Mohan and his descendants
This white Bengal tiger was namedMohan,The white tigers we see in the zoo now are basically his descendants.
Why does a white tiger have white fur and black stripes?
In the past, scientists generally believed that white tigers were caused by mutations in the tyrosinase (TYR) gene, which caused the animals to be unable to producepheomelanin(produces red and yellow pigments) oreumelanin(produces black and brown pigments), causing albinism in many species of animals.
Therefore, in the past, white tigers were also considered to be a form of albinism, but their albinoness was not complete.
However, the results of the whole genome sequencing of white tigers show that there is no abnormality in the TYR gene of white tigers. The real cause of white tigers losing their orange fur is a mutation in their SLC45A2 transporter gene.
This gene is the basis for the pigmentation of tiger fur. However, due to a genetic mutation in white tigers, the expression of pheomelanin in the fur is blocked through some unknown means, so orange fur cannot appear.
©Free.riders
but,This mutation does not affect the expression of eumelanin, so the black stripes of white tigers still exist, the eyes still have color, instead of being red due to a complete lack of pigment.
This genetic mutation occurs naturally in wild Bengal tigers, but it is a recessive trait, which means that both parents need to carry the mutated gene to have a white tiger.
It is believed that in the wild,The probability of a Bengal tiger giving birth to a white tiger is one in 10,000!
What needs to be pointed out here is that under normal circumstances,There is no problem with the health status of this white tiger, they are very rare in the wild and verypossibleThis is because their camouflage ability is poor and it is difficult for them to survive.
△ Disguised tiger
The reason why it is said to be "possible" is because the camouflage of a tiger is related to both its skin color and its stripes, while the stripes of a white tiger are not affected.
In addition, the white tiger actually has some advantages in its body.They are usually larger, the size of a male white Bengal tiger is between 200-300 kilograms, while the weight of an ordinary male Bengal tiger is only between 135-230 kilograms;
White Bengal tigers also mature faster——It only takes 2-3 years to reach full adulthood, while ordinary Bengal tigers take 3-4 years to fully mature.
Therefore, there may be other reasons why white tigers are rare in the wild.
△ A white tiger with almost no stripes, ©Averette
What happened to the other white tigers?
In the picture we opened with, there are two other types of white tigers, a whiter one (the second one on the left) whose black stripes have almost completely disappeared, and a white tiger whose black stripes are very obvious (the third one on the right).
Stripeless white tigers are even rarer than ordinary white tigers. They are actually caused by some genetic mutations that cause stripes to disappear, and these stripeless genes are likely to come fromsiberian tiger(i.e. Siberian tiger).
In captivity, people cross-bred white Bengal tigers with other subspecies of tigers in order to obtain white tigers of different subspecies, which eventually led to this genetic exchange.
In the case of unstriped white tigers, their white fur genes come from white Bengal tigers, while the unstriped genes may come from Siberian tigers.
In 2004, in a zoo in Spain, two normal-colored Bengal tigers gave birth to a white tiger cub with blue eyes and no stripes.
It can be seen that in a captive environment, the tiger's genes have been completely messed up.
△ A pseudo-black white tiger
There is another kind of white tiger with very obvious black stripes. This is actually a melanization phenomenon that can happen to all animals. It is just that the melanized individuals are white tigers, so their stripes only become extremely obvious.
at last
We mentioned earlier that people are trying to create white tigers of different subspecies through crossbreeding in order to make profits. In fact, since white tigers are recessive traits, the most effective way to obtain white tigers is to continuously inbreed to obtain homozygotes.
Most of the white tigers in existing zoos come from this way, and most of them are related to Mohan, the first white Bengal tiger to be successfully domesticated.
But what needs to be pointed out here is that theNot as rumored - all white tigers in captivity come from Mohan, because the relevant genes exist naturally in the wild.
In any case, it is a fact that most of the currently domesticated white tigers are the product of inbreeding, so they usually have serious health problems (because other recessive genetic diseases have also been expressed).
Many white tigers kept in captivity today look fine, but in fact they have defects in their vision, intelligence, immune system, etc.
The white Bengal tiger above is called Kenny. It is one of the victims of white tiger breeding. It has a short nose, a wide face, and obvious defects in its teeth. It can be seen from its appearance that it is not a normal tiger.
Fortunately, people are now aware of this problem, and in many parts of the world, the practice of breeding white tigers through inbreeding has been banned.
However, as long as people still prefer white tigers, this business will probably never stop.