The National Zoo's giant panda cub is squealing less often each day, and its mother has been catching up on some of the sleep she lost since its birth Saturday. But the two are so tightly intertwined that keepers have not had a good look at the tiny newborn.

The mother, Mei Xiang, is known by her keepers as a vocal animal, but she became quiet after the birth. It was not until Wednesday evening that she once again began making noises of her own. On at least two occasions, she honked for several minutes, a relatively common panda sound.

The Panda House is closed for at least three months to give mother and cub peace and quiet, and the zoo is not taking any chances -- an armed zoo police officer is stationed at the door. In a back den, visible only on camera, mother and cub are folded together in intimate embrace under the surveillance of keepers, volunteer monitors and thousands of people with Internet connections.

The birth was the first for Mei Xiang, who came to the National Zoo along with the cub's father, Tian Tian, on a 10-year loan from China in 2000. In exchange, the zoo is paying $1 million a year in privately raised funds for panda conservation projects in China. The birth of the cub adds an additional fee, according to zoo spokeswoman Peper Long: $100,000 a month for each month the cub survives, up to a maximum of $600,000.

The park's previous pair of pandas had five cubs in the 1980s, none of which lived more than four days. This cub will be a week old tomorrow. Cubs are extremely vulnerable -- until recently, only about half of captive pandas lived for more than a month -- but scientists have developed techniques that improved their odds.

The pinkish cub will be blind for several weeks. It has no fur and depends on its mother to keep it warm with her arm, paw or chin. Giant panda mothers may not leave their birth chambers for days. They help their infants locate a teat to suckle, and they lick them clean. Keepers say Mei Xiang has been a devoted mother from the start, tending to her cub's every need.

The volunteers monitoring the cameras have not been able to see or hear nursing, though they know it is going on. Some think the cub, a quarter pound at birth, has gained weight. The mother's protective grasp has prevented them from seeing its size, much less determining its sex.

"In a three-hour shift, maybe enough glances to make up two minutes," volunteer Molly Frantz said yesterday. "Maybe less than two minutes. It's very hard to tell. . . . The only time I see the cub is when she is about to reposition it."

Keepers had described the cub as similar to other restless newborns, squawking if its mother did something it did not like. At first, the cub seemed only to want its mother to sit up, her head slumped over her chest. By yesterday, Frantz said, the cub let Mei Xiang lie on her side or back without fussing. The cub squealed less frequently, and volunteers heard more grunting sounds.

"Mom and cub are working out quite a better relationship," said Frantz, a retired health policy analyst who lives in Friendship Heights. "She looks exhausted less so today. She is getting more sleep today."

As Frantz and other volunteers intently record observations that may someday increase the skimpy knowledge base about panda behavior, thousands of people are lining up to view mother and cub over the Internet.

At the American Zoo and Aquarium Association office in Silver Spring, spokeswoman Jane Ballentine said several people are keeping an eye on the newborn, whose species is endangered in the wild. The other day, when she heard the baby squealing, "I called everybody on my side of the office, 'Come listen to this!' " Ballentine said. "Getting that inside glance is kind of fun, knowing that no one will get in there" to the Panda House.

In Madison, Wis., Jacqueline Houtman has been watching avidly with her 6-year-old daughter. Her daughter knows the cub soon will get its black-and-white markings. Houtman thinks back to her own early mothering days.

"I keep remembering what it's like for us humans with newborns. Sleep, nurse, change diapers, repeat," Houtman wrote in an e-mail to The Post. "Mei just amazes me in her patience and fortitude. She never gets a break, does she?"

The National Zoo reports heavy traffic at its Web site. At Animal Planet, which also has cameras on its Web site, the panda cameras accounted for 10 percent of the traffic, spokeswoman Melissa Olear said. The company is making a documentary about the panda birth that is expected to air late this year or early next year.

The zoo is screening images from the Web cams in the auditorium of its main building when the room is not being used for meetings. The outdoor panda yard is open, and Tian Tian can be seen there when he is not cooling off indoors.

For now, because giant pandas are very sensitive to noise, the zoo has stopped construction of a new multimillion-dollar panda area that will be double the size of the current enclosure. Construction is continuing on adjacent sections of the new Asia Trail that are farther from the Panda House.

Female giant panda Mei Xiang cares for her newborn cub, outlined in the white box. The cub's sex has not been determined.