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A white tiger is a true enchanter. They are one of the most popular

zoo animals. Sadly, many have started to consider it as a freak or an aberration and not worth conserving at all. But now armed with the latest and precise information about its genetic roots indicating that, white tigers are the result of a rare but naturally occurring genetic variant within the wild Bengal tiger population, the voice to conserve these majestic beasts is gaining ground.

White tigers are extinct in the wild due to trophy hunting and their entire population now survives in captivity.

The jungles of India are the birthplace of the white tigers. The earliest record of white tiger is found in the Akbar Nama. It is recorded by Abul Fazal (accompanied by a painting) in the second volume of his work that in 1561 while Emperor Akbar was returning to his capital Agra from Malwa he encountered a big family of tigers – a tigress and her fi ve sub-adult cubs. Out of the fi ve sub-adult cubs two were white tigers.

A record of a white tiger from Poona (present Pune) was published in the Proceedings of the Zoological Society of London in 1891. From 1891 to 1922 white tigers were shot in Poona (Pune), Upper Assam, Odisha, Bilaspur and in erstwhile princely state of Cooch Behar (West Bengal).

Existence of white tigers has been recorded from Assam from time to time. In March 1889 a white tiger was shot in upper Assam. The Boga Bagh tea estate in upper Assam is named after the two white tigers that were found there in the beginning of the 20th century. In Assamese ‘boga’ stands for white.

In the 1920s and 1930s, fi fteen white tigers were shot in Bihar alone. The prestigious Journal of the Bombay Natural History Society of India (JBNHS) has recorded seventeen cases of white tigers shot in different parts of the country between the years 1907 and 1933. The fi rst instance of an exhibition of a white tiger in any proper organised zoo in the world was at the Calcutta (Alipore) Zoological Gardens in the year 1920.

The white tiger is a sight to behold. With the genetic mystery of the white tigers having been solved recently, the dwindling white tiger population could get a new lease of life.

SHAKUNT PANDEY

A white tiger

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Renowned hunter and later turned conservationist Jim Corbett in his famous work Maneaters of Kumaon has also casually referred to a white tigress whose pictures he had taken during the winters of 1938.

Historically, the area that is most closely associated with the white tigers is the erstwhile princely state of Rewa in Madhya Pradesh. The records of the tiger hunts were meticulously maintained at the Palace. There are nine recorded cases of white tigers from this region. The fi rst photograph of a live white tiger was published in the Journal of the Bombay Natural History Society (JBNHS) volume 27 of 1921. This white tiger was captured by the ex-maharaja of Rewa in 1915. The last white tiger was shot in 1947 by the ex-maharaja Martand Deo Singh. No wild white tigers have been heard of in Rewa since 1951.

However, Martand Deo Singh is also credited with raising the fi rst white tiger in captivity. It is from here that white tiger populations have grown in the zoos of India and other parts of the world.

In May 1951, a nine-month-old white tiger cub, which was later christened ‘Mohan’, was captured by Martand Singh from the forests of Rewa. He was

raised at the king’s Govindgarh palace. On reaching maturity he was mated with a normal coloured tigress christened ‘Begum’ who was also captured from the forests of Rewa. From 1953-56 they had 10 cubs in three litters but none was white coloured like the father. Mohan was then mated with his offspring ‘Radha’ from the second litter and on 30th October 1958 she gave birth to four white tiger cubs – three females and a male. A white tiger cub was born in captivity for the fi rst time ever!

Mohan and Radha had 14 cubs in four litters out of which 11 were white and three orange/normal coloured. Two white cubs of the second litter died within a few days of their birth. Mohan continued to breed for sixteen years and sired 34 cubs out of which 21 were white and rest of normal colour. He was the patriarch of the white tiger clan as the ancestry of many of the white tigers in the world can be traced back to him. He died on 18th December 1969 at the age of 19 years. He was laid to rest with Hindu rites and customs and a memorial was built in his memory at Govindhgarh palace which is visited by many.

The zoos of India and later the United States soon became the hub of captive breeding white tigers. But the

Association of Zoos and Aquariums (AZA) US banned the breeding of white tigers in all its affi liated zoos in the year 2011 thereby pushing the entire existing white tiger population of America in the private domain.

In India the captive white tiger population continues to thrive in its zoos. It is estimated that there are around 200 white tigers surviving in the world and half of these are in our country.

The Nandankanan Zoological Park of Odisha holds the Guinness book of world record for having the largest captive population of white tigers which is pegged at 34. Now there are plans afoot

Hunt of tigers (Two white tigers can be seen) by Akbar recorded in Akbar Nama

Ex-King of erstwhile Rewa princely state Martand Deo Singh – the man behind captive

breeding of white tigers

The fi rst live white tiger in captivity which was captured in 1915 in Rewa (Picture credit: JBNHS Volume 27, Year 1921)

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to establish a white tiger breeding centre at Mukundpur Zoo in Satna district of Rewa division in Madhya Pradesh.

The habits and behaviour of a normal coloured tiger and white tigers are more or less similar but fi ndings particularly in the US reveal that due to poor eyesight a white tiger tends to be more aggressive than the normal coloured tiger. There is no difference in their breeding season, litter size, gestation period and mating behaviour. The average life span is also similar varying from 16 to 20 years.

The colour of the coat of white tigers varies from white to off-white to cream with light brown to ash-grey stripes. They have mottled grey-pink nose pad instead of the pure pink colour as in normal coloured tigers; their eyes are ice blue or pale blue in colour.

On an average they are slightly larger and heavier than the normal coloured tigers. The average length and weight of a white tiger cub at birth is 53 cm and 1.37 kg respectively as compared to 50 cm length and 1.25 kg weight of a normal coloured tiger cub. An adult white tiger weighs 120 to 130 kg while the weight of a normal coloured tiger ranges from 105 to 120 kg (The White Tiger, JH Desai and AK Malhotra)

White tigers are not albinos. Albinism means lacking total colour pigment in the hair and the skin; even eyes lack pigmentation which gives a pink or reddish appearance. There is only one recorded instance of true albinism in tigers. It is reported in the Journal of Bombay Natural History Society Volume No. 28 that in the year 1922 in the erstwhile princely state of Cooch behar in a family of man-eating tigers consisting of a tigress and her four cubs, two cubs (a male and a female) were albinos with light colour coats and pink eyes. They were found in a very bad condition and they trotted around like big dogs before being shot. They also had long necks.

In mammals, fur colour is determined by the pigment melanin. There are two types of melanin – eumelanin (black to brown) and pheomelanin (red to yellow). The amount, ratio and distribution of eumelanin and pheomelanin in hair determine the coat colour of an animal. The white tiger is a rare colour morph of the Royal Bengal Tiger. Contrary to their orange coloured brethren the white tigers lack pheomelanin, with minor (or no) change in eumelanin, and have white fur interspersed with sepia-brown stripes.

Given sporadic but consistent

observation of white tigers in the wild over centuries of records, it is reasonable to speculate that the white tiger colouration is likely a stable genetic trait in a recessive manner. Data from white tiger captive breeding (The white tiger of Rewa and gene homology in the Felidae. R. Robinson, Genetica, 1969) has confi rmed that the striped white coat colour is inherited as an autosomal recessive trait.

The white tigers are considered to be leucistic and regarded to carry the recessive “Chinchilla” allele. This allele is known as the “inhibitor” allele because it inhibits pigment production.

Two pioneering research works by a team of Chinese scientists with the Peking University, Beijing, has removed the genetic mystery about the white coat of the white tigers – why the white tiger has lost its colour but has kept its stripes.

R. Robinson ibid in his work had postulated that white tigers arose because of a recessive allele at the chinchilla locus currently known as the tyrosinase gene. Xu et al tested Robinson’s hypothesis by sequencing the TYR (tyrosinase) gene along with other key coat-colour-associated genes MC1R (melanocortin 1 receptor), ASIP (agouti signalling protein), TYRP1 (Tyrosinase-related protein 1) and SLC7A11 (solute carrier family 7, member 11) in both white and orange tigers. No genetic association was detected among these genes, suggesting a different mechanism entirely.

Next, a genome-wide association study (GWAS) was conducted in a two-generation family of 16 tigers segregating at the white colour trait based on whole

Mohan, the patriarch of the surviving white tiger family (Picture credit: JBNHS, 1959, Volume 56)

Radha with her cubs – the birth of the fi rst white tigers in captivity (Picture Credit: JBNHS, 1959, Volume 56)

Mohan and Radha had 14 cubs in four litters out of which 11 were white and three orange/normal coloured. Two white cubs of the second litter died within a few days of their birth. Mohan continued to breed for sixteen years and sired 34 cubs out of which 21 were white and rest of normal colour.

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genome sequencing and restriction site associated DNA sequencing (RAD-seq). The approach mapped the white tiger colour coat colour trait to the gene SLC45A2 (solute carrier family 45 member 2). Further, an alanine to valine substitution (A477V) was identifi ed in SLC45A2 and found to be co-segregated with the white coat colour trait. This A477V mutation in SLC45A2 was validated in an additional 130 unrelated tiger individuals. A477V is located in the evolutionary conserved amino acid residue site, and predicted to affect the function of the SLC45A2 protein by three dimensional protein structure simulation. Xu Xiao et al. concluded that white tigers are caused by the A477V mutation in the SLC45A2 gene (The genetic basis of white tigers, Current Biology, 2013)

A recent study on felid coat pattern formation has identifi ed a key gene Edn3. This gene expression is increased in

dark-coloured regions compared to light-coloured regions. The pattern-sustaining mechanism is most likely to be conserved among felids, and perhaps tigers have preserved the region-specifi c expression pattern of Edn3 in the striped area. The scientists suggest that the A477V mutation in SLC45A2 may diminish melanin biosynthesis over the entire coat in white tigers, but the high expression of Edn3 sustains eumelanogenesis in some regions according to pattern specifying mechanisms, resulting in white tiger’s iconic sepia brown stripes (How the White tiger lost its color, but kept its stripes, XU Xiao et al. Science China Volume 57 October 2014).

Although deliberate inbreeding of white tigers has maintained their recessive colouration, it has also led to a host of health problems. It has resulted in sterility or reduced fecundity, shortened lifespan, vision abnormalities, shortening of limbs, twisted necks, crooked tails, kidney deformities, weakened immune systems, poor lactation in females and numerous still births.

Further, in the United States some white tigers of the North American line of white tigers suffered from a facial deformity known as bull-dog face, which is a distortion of the head, lacking bone development in the middle facial and upper jaw portion. The condition is characterised by a snubbed nose, domed head, jutting jaw, and wide set eyes with an indentation between the eyes. White tigers cannot see as well as normal tigers and suffer from photophobia. White tigers

A white tigress with her cub (Picture credit: Nandankanan Zoo, Odisha)

The habits and behaviour of a normal coloured tiger and white tigers are more or less similar but fi ndings particularly in the US reveal that due to poor eyesight a white tiger tends to be more aggressive than the normal coloured tiger.

with crossed eyes are not always born that way; they may develop the condition later in life. Parkinson’s syndrome has also been observed in white tigers.

The white tiger’s distinguishing characteristics arise from a single mutation, the substitution of one amino acid for another – valine for alanine – in the “solute carrier” protein geneticists call SLC45A2. Its job is to basically transfer specifi c molecules across cellular barriers. Similar variations in SLC45A2 have been observed in other vertebrate species ranging from humans to chickens. With rare exceptions the swap’s only effect on the animal is of external pigmentation.

The Chinese researchers who solved the genetic mystery of the white tigers say that since the crucial mutation in white tigers has been identifi ed it will be possible to identify and crossbreed pairs of Royal Bengal tigers, each one possessing a single copy of the recessive gene. Basic Mendelian rules give a 25% probability that any given pregnancy will produce white tiger offspring while signifi cantly expanding the gene pools of healthy animals.

Once wiped out due to the greed for trophy hunting, it is time we made sure that the roar of this majestic creature does not fall silent forever.

Mr Shakunt Pandey is a freelance journalist based in Kolkata. Address:-‘Lake Utsav’, P-331 Parnashree Pally, Flat No. 3A, 3rd Floor, Kolkata-700060; Email: shakuntpan33@gmail.com/shakunt_soumya@rediffmail.com