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201125DecSun

Genetic source for re-introduction of wild tigers in Kazakhstan too small?

published 25 December 2011 | modified 18 December 2016

In April this year, 2011, we were pleasantly surprised by a plan that was launched by the Kazakhstan government to reintroduce wild tigers in part of the country where the species went extinct in the last century. A unique tiger nature reserve will be established, according Prime Minister Masimov, in the southern part of the Lake Balkhash area, the original habitat of the Turan tiger, or Caspian tiger (Panthera tigris virgata). The Caspian tiger, which once ranged throughout the humid forests, mangroves and grasslands of Afghanistan, Turkey, Mongolia, Iran, Northern Iraq, Azerbaizhan, Turkmenistan, Uzbekistan and the Central Asian areas of Russia, was officially declared extinct in 1979, but last sightings have been in the 1950s. The plan's objective is to relocate Amur tigers, aka Siberian tigers, from the Russian Far East to suitable habitat in Kazakhstan. Research conducted in 2010 showed that the delta of the Ili River with its wetlands of lakes, marshes and thickets, provides this suitable tiger habitat. The Ili River flows into Lake Balkhash, Central Asia's second-largest lake.

Lake Balhash basinmap source: Wikipedia


The plan is one of the results of the ambitious Global Tiger Recovery Program that intends to double the number of wild tigers by 2022. This means that in ten years time the wild tiger numbers should increase from an estimated 3,200 to about 7,000 across the 13 tiger range countries.

Why Amur tiger ?

Recent research findings identified the Caspian tiger as genetically similar to living Amur tigers. This makes the Amur tiger (Panthera tigris altaica) the appropriate tiger subspecies as genetic source to use for reintroduction and repopulate the Lake Balkhash area. Although the extinction of the Caspian (Turan) tiger was due to poaching and habitat loss at the time, the area still retains suitable habitat, as stated before, and equally important it retains tiger's traditional prey animals, such as riparian deer, Persian gazelles and wild hogs. Therefore WWF-Russia expect that tigers can again roam the forests and landscapes of Central Asia.

Population viability ?

In a recently published article it is shown that the effective population of Amur tiger is fewer than 14 animals. So, how viable will the population of Amur tigers be? As it means that of the current population of about 500 Amur tigers the genetic diversity represents not more than just 14 animals. A very low genetic diversity like this makes the population vulnerable to disease and genetic disorders, as these will be easily passed on to the next generation. The scientists conclude that this small genetic foundation is due to expanding human settlements, habitat loss and poaching in early 20th century, which almost drove the Amur tiger to extinction. The few remaining breeding individuals, about 30, in the 1940s represented only a very small gene pool. This resulted in a loss of genes, and the tiger population has not recovered since from this low variety of genes.

A study which also looked at gene variety in Amur tigers in captivity, e.g. zoos, found a similar low variety of genes, but gene variants existed in captive animals which were lost in wild animals. I can imagine that these genes come from tigers which have been caught in the early 20th century and their offspring which have been kept in captivity since. Although the activities of the animal dealers in the beginning of the 20th century contributed to the current situation where Amur tigers are threatened with extinction, they perhaps now will contribute to their survival.

Isn't the present situation and Kazakhstan's plan an ideal opportunity to try and breed wild tigers with captive tigers? As this will increase genetic variety and therefore could increase genetic resistance and survival of Amur tigers in the wild. I do not know of many successful re-introduction into the wild of captive bred tigers, but trying to breed captive male and wild female tigers could work, I guess. If the male tiger still is able and willing to copulate with a wild female, and this tigress allows to be mounted by the male, their offspring could be raised in the wild, I suppose. Perhaps it has been tried before. If not, it is worth a try!

Apart from the viability of the potential tiger population the viability of the environment and its suitability for tigers in the long run is important. So, the question is if the Kazakhstan government, supported by Russian government, will be able to restore the Balkhash basin ecosystem and the water balance of the Ili-Balkhash basin. Since 1960, water levels in Lake Balkhash have been declining, due to evaporation and increased water usage for irrigation along the Ili and Karatal Rivers. To sustain a wild tiger habitat effectively will not be easy, but at least a first effort is made to kick-off what has been promised in St. Petersburg. And "Efforts to grow the global tiger population will certainly benefit from expanding the tiger's existing range," according to the manager of Asian species conservation for WWF.

 

(Sources: Tiger Territory; the Sixth Extinction website; ENS, 26.04.2011; BBC Earth News, 28.02.2011; Driscoll et al. 2009 in PLoS ONE; Russello et al. 2004 in Conservation Genetics; Henry et al. 2009 in Molecular Ecology; Alasaad et al. 2011 in Mammalian Biology)


Related blogs

Goal: 7000 tigers in the wild

Tiger range countries map

 

"Tiger map" (CC BY 2.5) by Sanderson et al., 2006.

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