Kenny, the Down Syndrome Tiger lived until 2008. His unique looks captured plenty of media attention, but scientists are not in agreement about his actual condition.
What it is
Down Syndrome is a chromosomal abnormality whereby the sufferer has an additional chromosome in all of their cells. The result of this condition in humans is the production of a rather flattened face and fold of skin at the inner edge of the eye. It is well known for mentally handicapping human children, but a little less so in tigers.
Number of chromosomes
Scientists raised questions about Kenny’s diagnosis because of the number of chromosomes within a tiger. Humans have 23 chromosomes and the syndrome is a result of chromosome number 21 being copied, whilst tigers only have 19 chromosomes. The picture of the tigers face above does lead us to think along the lines of Down Syndrome due to its flattened face but it is not clear that Kenny carried a 3rd copy of any of his chromosomes and no evidence that it could be matched to the twenty first chromosome within humans.
What seems most likely is that Kenny was the result of breeding within a limited gene pool. The White tiger is incredibly unusual and as a result there is all too much demand for them. It appears that as a result of the demand, too much in-breeding has taken place and resulted in his abnormalities rather than Down snydrome being the cause. It would seem shocking in humans, but the mother and father of Kenny were both brother and sister. Sadly, most of Kenny’s siblings either died at birth or at a very young age according to Patricia Quinn from Turpentine Creek Wildlife Reserve, which was where Kenny was kept from 2 years old.
One of the big advantages of having 2 copies of each of a humans genes is when mating, mutations that are damaging or recessive are not usually expressed. Having said that, if a human couple are closely related, a stronger chance of them both having the same rare gene will exist. This would mean that the children would have a 1 in 4 chance of inheriting the rare gene from both parents. As the breeding pool becomes narrower, the chances for the offspring increasingly become like a game of Russian roulette.
It is reported that even though there were abnormally large numbers of deaths in the litters from Kenny’s parents, the breeders would not give up. This was either ignorance of the ancestry and biological issues involved, or perhaps just greed driven by such an ‘in demand’ animal. Either way, it looks like everyone lost out as Kenny had a brother who was also deformed and as a result, neither of them could be sold. Both of them went on to die at under half the life expectancy of a captive tiger, which is around 20 years.
Patricia Quinn said that Kenny was a big hit with the visitors at the reserve. His unusual looks and friendly nature meant most visitors ‘fell in love’ with him. He shared his compound with his disabled brother for 8 years.
Whilst White tigers are uncommon, it makes this level of extreme in-breeding rare. Commercial drivers are often pushing the sensible limits of breeding in pets and it would be fair to say that the look Kenny had was not dissimilar to that of a Pug, which has been in-bred for a couple of hundred years. You can see the physical discomfort within many of these animals as they pant and wheeze in their attempt just to draw breath. We all know that within ‘purebred’ dog varieties, they are also likely to have a shorter life.
The shame for the White tiger is that they could have mated with regular varieties if it weren’t for our obsession with colour.