Siberian Tiger Endangered?
by Michael
(London, UK)
Siberian tiger - photo by Göran Bength (Flickr)
Is the Siberian tiger endangered? Yes, very much so despite the stable population and the personal concern shown by President Putin.
Putin you may remember took a personal interest in the conservation of the Siberian tiger. He probably did this for personal benefit - improved image - but he at least is taking an interest.
The big problem with the tiger, any subspecies of tiger, is not just the low populations but the sustainability of those populations. It could be argued that they are all, already unsustainable. We are getting the gradual drip feed of information about the lack of genetic diversity of the tigers.
The South China tiger is extinct in the wild and the ones in captivity labelled, "South China Tigers" are hybrids of the Bengal tiger - no South China tigers left!
The population of the Siberian tiger was down to about 20 to 30 cats in the wild in the 1940s due to the usual activities of humankind: destroying tiger habitat and shooting them.
Since then conservation work has allowed the Siberian tiger population to grow to around 500. The figure seems to be growing - I read it was 400 at one time - which is very unusual. Lets not forget, however, that this is a good estimate but past experience tells us that population estimates can be horribly optimistic (the Bengal tiger population was grossly overestimated by the Indian authorities at one time). People don't just count tigers, they have to estimate based on tracks, scats and camera traps etc.
The figure of 500, however, is still remarkably low. What is the minimum number of a species of animal for it to be sustainable? I read that it was about 500. And we should remember that the Siberian tiger habitat is split into two separate zones, separated by the Vladivostok to Ussurisk human development corridor, creating two "island" populations. These actual tiger populations from a genetic diversity point of view is much lower.
In research on genetic diversity in around 2009, the conclusion was that the 500 tiger were behaving as if they were 27 to 35 individuals.
New research reported on in Feb 2011 states that even that low number may be high. The population of Siberian tigers is the equivalent of 14 individuals. See Siberian tiger habitat for a bit more information.
My understanding of this is that due to the inbreeding that has naturally taken place over time because of low numbers, the tigers have become sterile due to poor sperm quality. Accordingly in terms or reproductive behavior the 500 or so Siberian tigers that now exist in the wild are in fact 14 tigers.
On that basis, I would have thought that the game is over. There can only be more inbreeding and a gradual decline in the prospects for survival of this subspecies of tiger - the largest incidentally.
There must be a threshold, surely, at which, things can only get worse; a line that has been crossed.
Is the Siberian tiger endangered? You bet. I wonder if we simply can't get our minds around the idea that the Siberian tiger is actually going to become extinct, whatever we do? Or am I wrong?
In domestic cat breeding, under these dire circumstances, breeders would outcross with other breeds of cat or random bred cats to widen the gene pool and increase genetic diversity. But you can't do that with the Siberian tiger because what you will be left with is a genetically healthy group of tigers that are no longer Siberian tigers but hybrids. At that point it would be arguable that the Siberian tiger as a subspecies would be extinct despite being labelled, "Siberian tiger".
I wonder actually if that is what is going to happen. We may have to cross breed the tiger subspecies to create one species of tiger that can at least survive.
The Bengal tiger population is much larger but still precarious at about 1,400. But these tigers are in a similar position as they are often in reserves that are too small and which create island populations leading to inbreeding. The classic wildcat confined to an island range is the Florida Panther and it is badly inbred. Its days are numbered.
The idea of creating a very large corridor of tiger habitat in the foothills of the Himalayas may be the saving of the tiger: The Tigers of Bhutan.
See more on the tiger generally.
See Göran Bength's photo on Flickr (opens a new window).
