(FILES) In this file photo taken on June 20, 2018, a Bengal tiger cools off in a pond inside a cage during a hot summer day at Alipore Zoological Garden in Kolkata. - Six different sub-species of tigers exist today, scientists confirmed on October 25, 2018, amid hopes the findings will boost efforts to save the fewer than 4,000 free-range big cats that remain in the world. The six include the Bengal tiger, Amur tiger, South China tiger, Sumatran tiger, Indochinese tiger and Malayan tiger, said the report in the journal Current Biology. (Photo by Dibyangshu SARKAR / AFP)