THESE HAPPEN TO BE BENGAL TIGERS.

White Tigers

by Ronald L. Tilson

Coordinator, CBSG Tiger Global Conservation Strategy (GCS)

Tigers are an Asian species, found from the frozen tundra of the Soviet Far East, south to the humid jungles of Malaya and Indonesia, and west to the hot, hardwood forests of India. There are five living subspecies; three others are already extinct. Current estimates put the world population of wild tigers at about 5,000-7,000, the most numerous race being the Bengal race, distributed among some 18 tiger reserves and sanctuaries of India (and a half-dozen in Nepal and Bangladesh), accounting for over two-thirds of all wild tigers.

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Every once in a great while, a white tiger appears in the wild. White tigers differ from ordinary orange tigers (if a tiger can be referred to as ordinary) in having ice-blue eyes, a pink nose, and creamy white fur with chocolate stripes. White tigers are not albinos; their color is caused by a double recessive allele. A Bengal tiger with two normal alleles or one normal and one white allele is colored orange. Only a double dose of the mutant allele results in white tigers.

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How frequently do white tigers appear in nature? No one knows. But we do know that in the last 100 years, only about a dozen such white tigers have been seen in India (white forms have never been reported for any of the other subspecies). During this same century, the Bengal tiger population has dropped from 40,000 to a low of 1,800 tigers, and approximately 100,000 have lived and died, suggesting that as few as one in every 10,000 tigers is white.

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The white tiger collection in North American zoos traces its ancestry to a single white male known as Mohan, captured in 1951 in central India. It did not take long for the Maharajah who captured him to figure out that the only way to produce additional white tiger cubs was to breed Mohan back to his daughter, who gave birth to the first generation of captive-born white tigers in this century. One of these granddaughters, Mohini, was bred with her uncle and half-brother, an orange male called Sampson. It was through Mohini that the white tiger line came to the United States through the National Zoo in Washington D.C., From there, two of Mohini's offspring, a brother and sister, were bred at the Cincinnati Zoo and their daughter, Kesari, founded the Cincinnati white tiger line.

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In Cincinnati, the inbreeding continued. Bhim, a white son of Kesari, was mated to his sisters Kamala and Sumita, and so on. Altogether, the average inbreeding coefficeint of the white tiger lineages is much higher that that of either Sumatran of Siberian tigers managed by the tiger SSP which is methodically working towards minimizing the average inbreeding coefficient of its captive population. This translates into a healthier population and decreases the probability of a number of reproductive and disease problems associated with inbreeding.

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An SSP is a breeding strategy followed by participating zoos that is designed to maintain small self-sustaining populations of endangered species in captivity. Every breeding recommendation is designed to minimize the average inbreeding coeffcient of the population and to equalize the genetic representation of each wild-caught animal ("founders" of the captive population). With some 63 such species blueprints in hand, zoos are increasingly becoming last-ditch refuges for endangered species, as a kind of biological (rather than biblical) Noah's ark. Already on board are several species now extinct in the wild that survive only in zoos, including Pere David's deer and Asian wild horses, and three additional species, the California condor, Arabian oryx, and black-footed ferret, are currently making their way back into the wild thanks to captive breeding.

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The white tiger controversy among zoos is a small part ethics and a large part economics. For example, the tiger SSP has condemned breeding white tigers because of their mixed ancestry (most have been hybridized with other subspecies or are of unknown lineage) and because they serve no conservation purpose. Owners of white tigers say white tigers are popular exhibit animals and help increase zoo attendance and, at $60,000 each, revenues as well. The same story can be applied to the selective propagation of melanistic leopards, white lions, king cheetahs, and other phenotypic aberrations.

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However, there is an unspoken issue that shames the very integrity of zoos, their conservation programs, and their message to the visiting public. To produce white tigers or any other phenotypic curiosity, directors of zoos and facilities must continuously inbreed, father to daughter, to granddaughter, and so on. At issue is a contradiction of fundamental genetic principles upon which all SSPs for endangered species in captivity are based. White tigers are an aberration artificially bred and proliferated by a few zoos, private breeders, and circus folks, who do this for economic rather than conservation reasons.