The National Zoo's newborn panda cub is squealing and murmuring in apparent vigorous health, while its mother, Mei Xiang, is gaining confidence and is utterly absorbed in caring for her baby, keepers said yesterday.

Relieved zoo officials said they were pleased that the cub, born early Saturday in a back den inside the Panda House, has done so well during its first critical hours. Panda infants are born blind, vulnerable to infection and so tiny in relation to their mother's size that they can easily be crushed. The infant weighed perhaps a quarter-pound at birth compared with Mei Xiang's 250.

Keepers might not be able to get near the cub for weeks because panda mothers are quite protective, but they can see and hear Mei Xiang and her infant via closed-circuit cameras that also can be seen on the zoo's Web site. Longtime keeper Brenda Morgan said they can hear "good wild squeals" and contented murmurs from the infant, as well as "rooting" noises that indicate it is nursing. Much of the time, the cub is hidden behind the mother's huge paw, but sometimes the keepers get glimpses of the baby the size of a stick of butter.

"When she is repositioning herself, she has it in her mouth," Morgan said. "It is amazing the way an animal that can crush bamboo is so gentle with this tiny baby. She holds it ever so carefully."

Mei Xiang is "refining her holding techniques" in response to her baby, Morgan said, and gaining confidence in her mothering skills. She responds instantly when the baby squeals, Morgan said, "but it's not squealing overmuch, like it's uncomfortable all the time." For an animal that "usually has a lot to say," Mei Xiang has been quiet. Although there is food and drink just outside her den, she appears to be concentrating too much on her cub to be interested in it.

"I think she is focusing on learning to be the best she can with this baby," Morgan said. "Her whole world right now is with this cub."

It could be awhile before she lets her attention wander. At the San Diego Zoo, which has had two successful giant panda births, it was five days before first-time mother Bai Yun took a drink after giving birth in 1999, nine days before she had anything to eat and two weeks before she left the den for long enough to let keepers give the cub a quick exam and ascertain its sex.

"If everything is fine, we just don't touch," said Carmi Penney, curator of mammals at the San Diego Zoo. "We might start thinking about it at four weeks of age."

The Panda House is closed to the public for at least three months to let mother and cub bond, but the outdoor yard is open, and the male, Tian Tian, can be seen there. Keepers encourage him to be outdoors, because otherwise the public could not see him, but Morgan said on hot days he will prefer to come into the air-conditioned Panda House.

"He seems to be quite happy in his routine," she said.

When mother and cub eventually come outdoors, they will be kept in a separate yard from Tian Tian, at least until the baby is weaned, to avoid even unintentional harm from the male, Morgan said.

Pandas are endangered in the wild, where only about 1,600 live in China, and are fickle breeders in captivity. The female is in heat for only two or three days a year, so artificial insemination is commonly used to help things along, as it was March 11 with Mei Xiang.

The National Zoo's previous pair of pandas had five cubs in the 1980s, but none lived more than a few days. Mei Xiang, who is 6 and whose name (pronounced "may-SHONG") means "beautiful fragrance," and Tian Tian, who is 7 and whose name (pronounced "t-YEN, t-YEN") means "more and more," have been mating, or trying to, since 2003.

With everything seeming to go well, keepers are beginning to let themselves think about the milestones to come. Pandas are born with a fine, white downy hair and begin to grow distinctive black fur when they are a week or two old. By five weeks, the cub should be sitting up. By early October, it should weigh 30 pounds and look like a smaller version of its parents.

The panda will be named by the Chinese when it is 100 days old. It is likely to be weaned at 18 months. And under the zoo's 10-year, $10 million loan agreement for the two adult pandas, the young panda will be sent to China when it is 2 years old.

Although keepers can't get close yet, Mei Xiang and her cub are monitored constantly via closed-circuit cameras.