Caspian tigers - some of the largest cats to ever live - that met a grim end in the middle of the 20th century may roam again in Central Asia, using a subspecies that is nearly identical genetically to them, scientists say. Until the mid-1960s when they were designated as extinct, Caspian tigers, which reached up to 10 feet long and weighed over 130kg, ranged from modern-day Turkey through much of Central Asia, including Iran and Iraq, to northwestern China.

The reasons for their extermination included poisoning and trapping promoted by bounties paid in the former Soviet Union until the 1930s, said researchers from the College of Environmental Science and Forestry (ESF) in  New York. Irrigation projects during the Soviet era destroyed the tugay woodlands - a riparian and coastal ecosystem of trees, shrubs and wetlands - and reed thickets that were critical tiger habitat and the cats' prey disappeared as the riparian habitat vanished.

However, there is a chance that tigers - using a subspecies that is nearly identical, genetically, to the extinct Caspian - could be restored to Central Asia. The study lays out the options for restoring tigers to Central Asia and identifies a promising site in Kazakhstan that could support a population of nearly 100 tigers within 50 years. "The territory of the Caspian tiger was vast. When they disappeared, the number of nations that hosted tiger populations was reduced by more than half," said Professor James Gibbs from ESF.

The researchers say introducing tigers in a couple of locations in Kazakhstan won't make a widespread difference immediately but it would be an important first step. They analysed scientific literature that revealed Caspian tigers once lived in an area about 800,000 to 900,000 square kilometres (km) in size, mostly within isolated patches of riparian ecosystems (land along rivers or streams). Generally, two or three tigers occupied an area that covered about 100 square km.

Spatial analyses based on remote sensing data indicated that options for Amur tiger introduction are limited in Central Asia. However, at least two habitat patches are potentially suitable for tiger re-establishment, both in Kazakhstan. When the researchers considered current land use and the low density of the local human population, they found the most promising site is the Ili River delta and adjacent southern coast of Balkhash Lake.

The team identified about 7,000 square kilometres of suitable habitat. Population models for animals that tigers typically prey on - wild boar, Bukhara deer and roe deer - suggest the area could support a population of between 64 and 98 tigers within 50 years if 40 to 55 tigers are introduced. The study was published in the journal Biological Conservation.