Nine-year-old giant panda Lun Lun has given birth to a cub in Zoo Atlanta in the United States.

The youngster was born just before 5 pm local time on September 6 (4:51 am Beijing time yesterday), according to the Chengdu Research Base of Giant Panda Breeding.

The cub is hairless, weighs about 4 ounces and is the size of a human hand. The sex will not be known for weeks.

The delivery lasted 36 hours, the longest known delivery for pandas in captivity in the world, said Wang Chengdong, assistant to the director of the base. It generally takes a panda between two and 18 hours to give birth.

Lun Lun is responding normally to her new baby, holding the cub and reacting when it cries, said Dwight Larson, vice-president for animal programmes and science for the zoo.

The first few weeks of a cub's life are critical to its survival, Larson said. "These are small offspring and quite fragile," Larson said. "It's going to be tense for us."

Cubs typically take about 75 days to open their eyes. At 100 days, the zoo is planning a naming ceremony for the cub and to present it to the public.

The cub's mother Lun Lun and father Yang Yang are from the Chengdu Research Base of Giant Panda Breeding. They arrived at Zoo Atlanta in 1999 on a 10-year loan from the Chinese Government.

In 2004 and 2005, Lun Lun became mature sexually. She then had artificial fertilization but did not get pregnant.

In early spring this year, the Chengdu research base sent a panda expert to Atlanta, who worked with the American team to improve sperm collecting techniques.

"The expert from the Chengdu Research Base of Giant Panda Breeding used sperm collected from Yang Yang to do artificial fertilization," Wang said. The two pandas did not have sex.

"Lun Lun became pregnant and gave birth 158 days later," he said.

The panda birth in Atlanta is the fifth such birth in a US zoo in the last six years.

Source: China Daily