A common misconception is that all white tigers descended from just one tiger – a rather unhealthy state of affairs if it were true, as it would mean a very limited gene pool !
Update May 2017: There is a new analysis of founders for the white tiger population in India, based on much more complete data. This is presented as a graph showing 24 founders joining and 5 leaving the gene pool, a map showing diverse origins of the founders, and ancestry charts. It can be read here: White Tigers Today – Are They Inbred? More complete data for USA is not yet available.
“But aren’t they all descended from Mohan ?”
While it is probably true that all are descended from Mohan of Rewa, this does not mean he is their ONLY ancestor. For starters, it takes two to tango, so we must add Mohan’s mate Begum into the list of founders. Then, there were 2 other unrelated lines of white tigers – the Orissa line in India and the American line – so we must add them to the list too.
But the list doesn’t stop there either, because every time a new, unrelated tiger contributes its genes into the pool we must add that tiger to the list of founders too.
Scroll down for these tables, but first there are a couple of things to know.
What qualifies a tiger to be a “founder” ?
A founder is a known ancestor that is considered to be unrelated to any of the other founders. Founders are all the tigers who have contributed their genes to the population – genes which are then passed down through the generations. (The white gene itself may have come from only a few tigers, but this is only 1 gene amongst 1000’s.)
Note that a founder does not have to be white – orange tigers can have white descendants too if they are bred to a tiger with the white gene (Ref White Tiger Genetics: The Basics).
Source of the Data Used
The source data used does not cover ALL white tiger breeding, (in particular private breeding) from all time periods, or from all countries. So these figures represent only a portion of the white tiger population – if complete data were available there would likely be more founders to add, and there may be some founders leaving the gene pool if their line died out.
- White Tiger Studbook by AK Roychoudhury, 1989.
- International Studbook of Bengal Tigers, Dec 2012 (does not always state if a tiger was white)
- USA Genealogy charts 1964-1993 (with a small amount of later data)
Results of the Analysis
USA: Up to 1993 there were at least 15 founders of the USA lineage of white tigers, with an additional 8 possible founders, (plus any more not included in the source data.)
Table 1 shows the number of USA founders increasing over the years as new blood (and genetic variety) was introduced by outcrossing.
Anecdotal evidence suggests that the outcrossing trend continued, with more unrelated tigers added to the gene pool in the years after 1993. For example, the International Studbook shows 5 tigers of the Orissa lineage exported from Nandankanan to Texas, USA. If any of these tigers were indeed used for breeding, that would add 3 more founders into the USA population.
INDIA: Table 2: Up to 2011 there were at least 17 founders of the India lineage, with a further 11 possibles (plus any more not included in the source data).
How does this compare with official captive tiger populations?
Table 3 shows the number of founders in official tiger captive breeding populations, for various dates, along with the white tiger numbers for comparison.
Source of data:
- 1987: Tigers of the World 1987, Ed. Tilson & Seal, p43
- 1997: Management and Conservation of Captive Tigers Ch 8, Tilson,Traylor-Holzer,Brady
- 2002: AZA Annual Report of the Tiger SSP
- 2014: Tiger Species Survival Plan
At least 30 tigers have contributed their genetic variety to the white tiger gene pool, a number comparable to official tiger breeding plans.
The number of founders is only one factor to consider when assessing the health of a population. However, it is a factor, and the figures show that the myth that “all white tigers descended from only one” – a very unhealthy state – is far from true.
The information from which this figure is derived is incomplete and does not represent the full current global situation, so it should be used as an indication rather than as an absolute value.
Uncertainty About Some of the Founders.
Where a founder turned out to be a white gene carrier (eg Susie or Buck) it was often assumed that the tiger “must have been” descended from Mohan, even though there was no genealogical evidence – based on the notion that Mohan was “the first” white tiger.
This is not true, as the white gene was already present in the captive population of tigers long before Mohan was born. For example, way back in 1892 a white tiger was born in Adelaide Zoo in Australia, along with his orange sister. The parents were born to circus tigers from overseas. (Refer to Illustrated Australian News,1892 Oct1, p19, for an example of the news coverage of this white tiger)
In 1809 a white tiger was kept in the Royal Menagerie at the Tower of London – did he breed and pass on the gene ? (Ref Records of White Tigers in the Wild)
Similarly, the Orissa line in India was founded when a surprise white cub was born from parents with no links to the Rewa line. There were likely even more tigers in captivity already carrying the white gene.
White gene in Amur tigers in USA?
My analysis assumes that the white gene in the American line came from the Bengal tiger Susie (mated to Amur Kubla). However, there is a suggestion that it may have come from an Amur tiger, instead of, or in addition to, the Bengal. This is entirely possible, as there is historical mention of white tigers in Siberia. If so, there may be more founders to add to the list…