India, Sept. 8 -- Three Sumatran tiger cubs born at a zoo near Athens are offering fresh hope for one of the world's most endangered tiger species, as zoos work to maintain a backup population for possible future reintroduction into the wild.

The two-month-old cubs received identification microchips and their first vaccinations on Tuesday at Attica Zoological Park as part of a global conservation effort to build a safety population of the species.

The Sumatran tiger is classified as critically endangered by the United Nations and conservation groups and is found only on Indonesia's Sumatra island, which is slightly larger than Sweden. As few as 400 are estimated to remain in the wild, with aggressive forest clearing among the main threa...