WASHINGTON - A western lowland gorilla was born Saturday at the National Zoo in full view of visitors and a volunteer, zoo officials said.

The mother, Mandara, was cradling the baby to her chest, and staff had not yet gotten a close enough peek yesterday to say whether it is male or female. Mandara's palm covers the baby's body, believed to weigh between 4 and 5 pounds, but its head and one arm are usually visible, zoo spokeswoman Pamela Baker-Masson said.

"She's very unlikely to set it down," Baker-Masson said. "Sometimes the hand was in a little ball, and sometimes the hand is spread out."

Mandara gave birth about 1:45 p.m. behind a large plate-glass window. A volunteer interpreter realized what was happening and alerted spectators in the ape house.

"Most animals give birth in the middle of the night or early in the morning" or go into a den or more private off-site area, Baker-Masson said.

Mandara is 26 years old, and had given birth five other times over the years. This baby's father is Baraka, who is 16.

The baby will be raised in the ape house with siblings Kigali, Kwame and Kojo, Baker-Masson said. A gorilla named Haloko also lives in the ape house; all the gorillas, who live as a family, will remain on exhibit.

"This is a very critical time for the survival of the infant, and all precautions must be taken to ensure that Mandara and her baby are in an environment that is comfortable, safe and controlled," said Don Moore, associate zoo director for animal care. "Mandara is a very experienced and competent mother, and we're confident that she will properly care for and bond with her baby."

Western lowland gorillas are on the International Union for Conservation of Nature and Natural Resources Red List of Threatened Species. They are critically endangered primarily because of habitat loss, fragmentation and poaching.

The gorillas, which are native to tropical forests in West and Central Africa, are also a focus of the National Zoo's participation in the Species Survival Plan, in which North American zoos collaborate to develop a self-sustaining zoo gorilla population.

Mandara was born at Chicago's Lincoln Park Zoo, and is owned by the Milwaukee Zoo. She came to the National Zoo in October 1985. Baraka was born at the National Zoo to Haloko and Gus.