Dialogue One
Kid: Mummy, who is my daddy?
Mummy: Forget about daddy, dear child. You have to learn how to be strong and independent, and I am going to teach you how.
Kid: But all the other animals have their daddies… (looks sad)
Mummy: Listen kid, daddy doesn’t really know and care who you are. He has left us to fend for ourselves. One day, you might even have to fight against him...
Kid: But why would daddy want to fight me? Doesn’t he love us anymore...? (tears start to well up in his eyes)
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Fig. 1 Tiger Cubs at Amersfoort Zoo 1
Tigers are generally solitary animals. They live alone, hunt alone, do everything alone (there are however two exceptions), and only come together during mating seasons. After they mate, they go their separate ways (of course they don't in the zoo :P), and the female, who becomes impregnated (not 100% but highly probable) with a child/children, will have to hunt for food all on her own, for herself as well as her future little cubs.
So when are tigers seen together? The first is pretty obvious - it is during the mating season. According to the website Tiger Territory 2, there is "temporary fidelity in tigers" 3; the tigers are seen hunting together and they remain monogamous to each other. However, this only lasts through the mating season.
The second scenario in which tigers are seen together is when a tigress hunts for food together with her children. As the tigress is solely responsible for the upbringing of her children (due to the extreme irresponsibility of the father of the cubs, in my opinion that is :X), she has to teach her cubs how to hunt for food, so that they would not die of hunger once they mature and become independent.
Usually the tigress will move to a new area when impregnated, if she is unsuccessful in driving away juveniles from her range. She does this to seek a "solitary and safe area for the cubs" 4. This reduces the threat to her cubs and it also reduces competition for food.
What I think:
Here, I believe, is a result of natural selection. Over time, the tigress realises that there will be less food for everyone in the same territory if more tiger cubs joined in. In addition, the territory of a tigress is three times smaller than that of a tiger 4.
A tigress' care for her cubs may seem to be unusual, as opposed to other big cats like the lions. It is known that the lion cubs are being cared for in a pride, and therefore the job of raising cubs does not fall on the lioness' shoulders alone. In addition, the lions will feed on their meal first before the cubs get to eat, and in fact, they are also known to feed on their own offspring at times. However, if we think about it, unlike the lions, a tigress is the sole breadwinner of her litter. If she does not care for her cubs, by natural selection, her cubs will certainly lose out to the other bigger cats out in the wild. It seems then, that her care for her cubs is probably to ensure a higher survival rate.
There are probably other times where the tigress reunites with her older cubs, as well as the tiger who mated with her, but this only occurs if they do not pose a threat to her offspring.
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Dialogue Two
Kid: Mummy, why are my cousins white? Are they different from me?
Mummy: Why, no, dear. They just have different colouration.
Kid: But why? They have white coats, blue eyes, pink noses and pink paw pads... they look so different from me! (Looks puzzled with bright inquisitive eyes)
Mummy: Well you know, it's the same with the dark-haired and blonde humans out there. Having a white coat is coded for by a certain mutated gene ('allele' to be exact, but Mummy is trying to avoid being overly specific), and it is only expressed if the child gets this gene from both parents. That is, this is a recessive mutated gene. (Mummy tried her best to be less scientific but seems like it is not working)
Kid: Huh? (Looks even more puzzled than ever)
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The limelight of this post is really on the Bengal Tigers, also known as Panthera Tigris Tigris in the scientific community.
Fig. 2 A "Golden Tabby" - another colour variation of Bengal Tigers. 6
Among the Bengal Tigers, the White Bengal Tigers are highly popular among visitors of zoos who house these tigers. Contrary to popular belief, these white tigers are not subspecies of tigers. They simply have slightly different genes but they still belong to the Bengal Tiger species. As illustrated in dialogue two above, the white colouration, blue eyes, pink noses and pink paw pads are results of a recessive mutated allele, and are only expressed if the child inherits this recessive allele from both parents. This means that both parents are carriers of this mutated gene, although they need not express this allele since it is recessive.
As these White Bengal Tigers are extremely rare, it is highly prized among humans. Whatever the reason is, some humans have been breeding these white tigers together to obtain yet more white tigers.
However, this is extremely cruel to these tigers. Inbreeding, over long periods of time, results in deformities of the digestive tract, organs, skeleton, as well as eyes. Such deformities include crossed eyes, twisted necks and cleft palates 7. In addition, there's limited variation to their gene pool, which makes them highly susceptible to environmental changes. There's also high infant mortality rate as a result of inbreeding.
Fig. 3 White Tiger Cubs 8
What I think:
Again, I believe that this is a rather good example of natural selection - of why it is better to have a diverse variation in one's gene pool.
One should note that in the wild, there's no preference for white tigers to mate with white tigers. In fact, the white colouration is very disadvantageous to the tiger as it is harder for white tigers to camouflage in a jungle setting. Tigers need camouflage for hunting, to get nearer to their prey in order to catch them. That's because their prey are usually fast in escaping, and the weight of tigers makes it impossible to sustain high speeds for long periods of time. It seems logical then that a white tiger would prefer mating with another tiger of a different colour, to ensure a higher survival rate of her offsprings. It is speculated that the rarity of a white tiger is not solely because of the rare frequency of the mutated allele for the white colouration, but rather, due to the white tiger's inability to hunt as effectively as its orange peers (due to its magnificent snow-white colour), resulting in starvation and ultimately, death in its early years (before maturing and mating, which is essential for passing down its genes).
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Here's a poem for you to enjoy! :)
The Tiger
1757-1827
TIGER, tiger, burning bright
In the forests of the night,
What immortal hand or eye
Could frame thy fearful symmetry?
In what distant deeps or skies
Burnt the fire of thine eyes?
On what wings dare he aspire?
What the hand dare seize the fire?
And what shoulder and what art
Could twist the sinews of thy heart?
And when thy heart began to beat,
What dread hand and what dread feet?
What the hammer? what the chain?
In what furnace was thy brain?
What the anvil? What dread grasp
Dare its deadly terrors clasp?
When the stars threw down their spears,
And water'd heaven with their tears,
Did He smile His work to see?
Did He who made the lamb make thee?
Tiger, tiger, burning bright
In the forests of the night,
What immortal hand or eye
Dare frame thy fearful symmetry?
___________________________________________________________________________________________
Footnotes
1 Courtesy of Dear Kitty. Some Blog http://dearkitty.blogsome.com/2006/05/19/tiger-cubs-born-see-video/
2 Tiger Territory http://www.lairweb.org.nz/tiger/
3 Tiger Territory - Habits of the Tiger - Mating - Copulation (page 4) http://www.lairweb.org.nz/tiger/mating4.html
4 Tiger Territory - Habits of the Tiger - Raising Cubs - Learning to Hunt (page 5) http://www.lairweb.org.nz/tiger/family5.html
5 Tiger Territory - Habits of the Tiger - Mating - Fighting for a Female (page 2) http://www.lairweb.org.nz/tiger/mating2.html
6 Courtesy of The Nature Sanctuary Gallery http://www.naturesanctuary.org/gallery.html
7 White Tigers - Inbreeding Depression & Genetic Anomalies http://www.messybeast.com/genetics/tigers-inbreeding.htm & Big Cat Rescue - White Tiger Fraud http://www.bigcatrescue.org/cats/wild/white_tigers.htm
8 Courtesy of Musings of the Hearth http://scv.bu.edu/~aarondf/hearth/archives/cat_links.html
References and Bibliography
1. Tiger Territory. http://www.lairweb.org.nz/tiger/mating4.html
2. Bengal Tigers. http://www.bengal-tigers.org/bengal-tigers-facts.htm
3. White Tigers. http://www.natureobservers.com/snowtiger/
4. White Tigers - Inbreeding Depression & Genetic Anomalies. http://www.messybeast.com/genetics/tigers-inbreeding.htm
5. Big Cat Rescue. White Tiger Fraud. http://www.bigcatrescue.org/cats/wild/white_tigers.htm