The Sacramento Zoo welcomed the surprise birth of a Sumatran tiger cub Thursday.

The 2-pound baby was born to Bahagia, a female and Castro, a male. It was the second litter for the pair who had three males cubs in November 2006.

A second cub born Thursday had severe head injuries and did not survive, said zoo spokeswoman Lauren Kraft.

Sumatra tigers are a critically endangered species and are only found in the wild on the Indonesian island of Sumatra. About 200 live in captivity.

Zoo veterinarians performed an ultrasound on Bahagia in December, Kraft said, and no fetuses were present. Animal caretakers did not see a significant weight gain or behavior change with the mother; hence the cub’s arrival was a surprise.

Kraft said the cub will bond with its mother and gain strength over the next three months in their den and away from the public eye. Baby tigers are born with their eyes closed.

The cub appeared healthy, Kraft said.

Earlier this week, the zoo lost the first Giant anteater born there. The baby was born March 9.