Genetics, habitat, cubs and territories



The White tiger is not a separate sub-species of tigers. They are in principle just White Bengal tigers. Sometimes, White tigers are referred to as Snow tigers. However, Snow tigers are White tigers without stripes. White tigers do have visible stripes.

The color of White tigers can be attributed to a special pair of recessive genes on their chromosomes.

White tigers have become quite common in Zoo's in the United States, Europe and Asia. This is due to a single White tiger imported from India. Since then especially private people and a few Zoo's have done a lot of breeding - and inbreeding - to promote the white color gene. They even mixed White Bengal tigers with the larger Siberian tigers to get larger specimens to attract more Zoo visitors.

Inbreeding leads to an increased homozygosity among those individuals affected by it which is harmful to them. Typically inbreeding leads to more unfit individuals. In the case of tigers this is that individuals are much worse at doing things normal (not inbreed) tigers are capable of.

The name Siberian tiger is by the way also a bit misleading, as Siberian tigers do not live in Siberia - they live in the Amur Region of South Eastern Russia close to the Amur and Ussuri River. The best name for the Siberian Tiger would probably be the Amur tiger.

Zoo employee takes care of White tiger cub.


Genetics

In nature, White Bengal tigers arises from the mating of two Bengal tigers with recessive genes for the white color of fur. The gene is recessive has the effect that offspring (cubs / kittens) only become white if they inherit the recessive gene from both parents.

It is the same principle as with brown and blue eyes. The inbreeding producing all these White tigers is neither good nor healthy for the tigers. In nature White tigers have, at least theoretically as there probably arent any, a less chance of surviving than normal colored tigers due to their lack of camouflage compared to the normal Yellow Tigers.

Below is a very simplified illustration (Fig 1) of how the transfer of genes coding for fur color works. Consider to yellow Bengal Tigers mating. If they are both carriers of the recessive gene there's a 25 percent chance that their cubs will be white. If a white and a yellow Bengal tiger mates there's a 50 percent chance that the offspring will be white. The chances of getting more White tigers can be enhanced by letting tigers that are related mate. This is however the definition of inbreeding.

two sweet looking cubs of the white tiger

Fig 1.Illustration of how genes control the color of White tigers.

Sometimes the talk about species and sub-species can be a little bit confusing when it comes to tigers. The distinguishing between species is based on morphology rather than genetics, because the latter wasn't invented when the sub-species were defined. Snow Tiger have never been an independent species - they are "just" a beautiful variation of the Bengal Tiger.

The future of the Bengal Tiger and the White Bengal Tigers does not look very bright. The population of White tigers outside captivity is hard to estimate, since they are not seen very often in their natural habitat. The population of Bengal Tigers is split into several very small groups of tigers, each of them probably too small to sustain a healthy population without inbreeding in the long run.

The number of White tigers among the population of Bengal tigers solely depends on the frequency of the recessive gene within the population. It is however a fact, that inbreeding produces more homozygotes - the relative frequency of either WW or YY homozygotes will increase in a population declining in numbers due to inbreeding.

A male White Bengal tiger normally reaches a weight of 400-500 pounds, while a female normally weights 300-400 pounds. Larger individual have been observed. For more information about the appearance of the White tiger I suggest the video or picture section of this webpage.

Habitat

The White tiger is found in Bangladesh and the Eastern parts of India, Nepal, Himalaya and Burma and the Bay of Bengal. It lives in all sort of environments such as forests in high altitudes, mangroves, arid and swampy areas. It has been said, that the best chance of seeing a White Bengal Tiger is in Himalaya, but this is probably not true anymore.

Winter temperatures in the United States and Europe do not pose any problems to any tigers, so tigers in captivity don't suffer in that respect. Tigers need a large area where they can hunt because they demand large amounts of meat to feed themselves and their cubs.

Cubs

Cubs from White tigers are either white or yellow. It's all random and it's not uncommon to see cubs with different colors in the same litter (Fig 2). The litter size of Bengal Tigers is anywhere from 1 to 4 cubs depending on chance and the availability of prey for the female. The most common litter size is however two kittens.

The pregnancy last for only 15 weeks. The cubs are born blind, just like notmal cat kittens. The cubs stay with there mother for 2-3 years. For the first 8 weeks the cubs only gets milk but from then on they will gradually swift to eating meat and after 6 months they are weaned off.

The father of Bengal Tiger cubs doesn't help in raising the cubs, but he's important in the sense that the female is in his territory. If another male Tiger conquers the territory, the cubs are in danger of being killed by the new male. The advantage of this behavioir is that the strongest male won't have to compete with the offspring of weaker tigers in the future. Furthermore the female tiger will be me more prone of having his cubs in the future.

Fight for territory among Tigers

Males fight for territory in order to impregnate as many females as possible - thereby promoting their own genes. Females fight for territory to sustain and to feed their cubs. There can be several tigers on the same territory. It's also very common, that female offspring stay close to the territory in which they were raised.

Javan tiger

The Javan tiger with the Latin name Panthera tigris sondai lived on the Island of Java, Indonesia. This sub-species of the tiger were extirpated somewhere between 1950 and 1980. Unverified reports tell that a small population of the Javan tiger may thrive deep into the forest of Java.

In the Meru Betiri National Park there's is a large inaccessible area where there might be some few species left, but its very improbable.

Evolution of tigers

There exist 37 different species of cats. Cats evolved around 25,000,000 years ago and have been and are some of the most specialized mammals on the earth. The siberian tiger is the largest cat in the world. the snow tiger is slightly smaller than the siberian tiger. Back in history larger cats have existed, but they were extirpated long time ago.

The last Tasmanian Tiger diet in 1936. It is heartbreaking that such as fine animal is now extinct. Below you can see a video of this beautiful tiger.

In general cats are very alike both in terms of their way of living and their behavior. They are especially adapted to hunt, kill and eat raw meat! All predators are adapted to hunting and eating meat and a special kind of living one could say, but the tigers in general, including the Snow Tiger, is perhaps more adapted than many other predators. Humans for example have relatively flat molars that we use for chewing food.

The main reason why the tiger became extinct was destruction of its habitats. Forest is chopped down for firewood or forest areas are converted into agricultural land.

Javanese farmers didn't like the tiger because it constituted a threat to their livestock animals and chased it a way. At some point the population of tiger became so small that it was impossible to sustain a healthy population of a mix of breeding, old and young tigers and the population slowly decreased.

History of tigers

Historically speaking tigers has inhabitated most of Asia, parts of Russia and the huge areas between the Aral and Caspian Seas. There are eight subspecies of tigers. Unfortunately three of them were eradicated in the last century - the Javan tiger, the Bali tiger and the Caspian tiger.

The different types of tigers or subspecies are usually defined by their body size, the characteristics of their skull and their coloration and striping patterns. This division might prove inadequate compared to DNA analysis since morphological distinctions usually have been based on a few specimens. Research has also revealed, that the variation of some characteristics overlaps between subspecies from time to time making distinctions difficult.

Tigers require quite large land areas for hunting, mating etc. According to both ecological analysis and model predictions of tiger densities, an average density of tigers from 3.2 to 16.8 in 100 km2 is required for a tiger population to sustain. This area is closely related to the density of the tigers prey which of course wary from area to area. The requirement of tiger of large land areas in combination with habitat destruction is one of the main reasons why its difficult to uphold thriving populations.

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