WASHINGTON — Washington zoo revealed on Monday that its new panda cub is male, six weeks after webcam footage of his mother Mei Xiang giving birth was watched around the world.

A swab from the cub’s cheek was taken for DNA analysis, as male and female giant pandas appear similar at birth.

“The cub appears to be healthy and strong,” the Smithsonian’s National Zoo said, adding he weighed 3.6 pounds (1.6 kilograms) and measured 14 inches (35 centimeters) from nose to tail tip.

“Both of the cub’s eyes are starting to open. Keepers are encouraged by his progress,” it said.

A blue painting — by Tian Tian, the cub’s father, who made daubs on a canvas while holding a brush through his cage bars — was unwrapped by zoo keepers to reveal the cub’s gender.

Mei Xiang, 22, is the second oldest documented giant panda in the world to give birth. She was artificially inseminated in March with frozen semen from Tian Tian, 23.

Mei Xiang has now given birth to four surviving offspring.

All cubs born at the zoo move to China when they are four years old under a partnership contract in which China owns the pandas.

Fewer than 2,000 giant pandas still live in their natural habitat in China, while some 600 more live in zoos and breeding centers around the world, according to the Washington zoo.

The unnamed cub and his mother can be followed via a webcam on the zoo’s website.