SPATA, Greece — The world’s most endangered tigers have started a family in Greece, offering hope for a predator that is rapidly vanishing from the wild.

Three 2-month-old Sumatran tiger cubs received identification microchips and their first vaccinations Tuesday at a zoo near Athens, as part of a global effort to build a backup population.

The Sumatran tiger, classified as critically endangered by the United Nations and conservation groups, is found only on the Indonesian island of Sumatra, which is slightly larger than Sweden. As few as 400 are believed to remain in the wild, mainly because of aggressive forest clearing.

“The Sumatran tiger is one of the most threatened tiger species in the world, and among felines in general,” said Theodoros Babilis, head keeper of cats and monkeys at Attica Zoological Park.

Zoos in Europe and elsewhere are maintaining a safety population, he said, “so that in the future there can be potential reintroductions of this species into the wild.”

The Sumatran tiger is the smallest tiger species in the world, but males can still grow up to 2.55 meters (8.4 feet) long and weigh as much as 140 kilograms (309 pounds).

Skilled swimmers and climbers, they use their dark stripes — unique to each animal, like a fingerprint — to hide in the dense forest as they hunt deer, wild pigs and smaller mammals.

Even at 2 months old, Babilis said, the cubs have already developed sharp claws and teeth that make handling them a challenge.

The cubs were born in early July to Toba, their mother, and Argos, their father, who has since died of cancer. The surviving cubs are expected to take names from characters in Homer’s “The Odyssey,” zoo staff said.

Two males and one female, the cubs were restless during Tuesday’s vaccination. Veterinary staff needed help to complete the procedure, ferrying the animals back and forth in carriers on electric buggies.

Caring for the animals is demanding work, said Dr. Arsenoi Psaroudaki, a zoo and wildlife veterinarian.

“The tigers don’t like to be handled. They’re very wild,” she said, explaining that staff have to work quickly to limit stress.

The cubs received microchips logged in a shared database, plus a vaccine similar to one commonly given to cats that protects against three diseases.

For Psaroudaki, the work is also rewarding because it offers “some hope for safeguarding these really rare cats.”

She added: “It’s very humbling to be able to work with the rarest tiger species in the world.”

—— Theodora Tongas in Spata, Greece contributed