Late at night, in the quiet of the National Zoo’s shuttered giant panda house, those keeping watch over the fragile new cub listen for the sounds of the routine.

The squeaks of the three-day-old animal. The faint sound of its nursing. The contented bamboo munching of its father, Tian Tian, in a neighboring enclosure.

Because the cub’s mother, Mei Xiang, has kept it enveloped with her body, no one has gotten more than a fleeting look since it was born Sunday night.

A glimpse of something the size of a large mouse held gently in Mei’s mouth was captured on the panda cam in a clip released by the zoo Tuesday. But it was brief and blurry.

So the 24-hour-a-day cub watch is conducted by ear as well.

The zoo has put a team of keepers and a senior biologist on duty in the panda house, along with the volunteer panda-cam monitors, to make sure nothing goes awry with the cub.

The staff stays in the keepers’ office a few steps from the enclosure where Mei has the cub in a large nest of bamboo inside her secluded den.

For the keepers, there is an air mattress, and there are incubators, blankets, and formula for the cub, in case of emergency.

The zoo is not anticipating trouble, but four giant panda cubs born there during the 1980s, including a set of twins, died shortly after birth from pneumonia and other infections. And a newborn red panda cub died in 2010.

The giant panda cub probably weighs about four ounces, zoo officials have said. Its mother weighs about 230 pounds. So the staff must be vigilant.

“That’s our job,” said veteran zoo biologist Laurie Thompson. “It’s a lot of pressure. . . . We have the responsibility of this new cub and the mom. But we take it willingly, because we love the animals.”

Thompson, 41, who was the first person to examine the zoo’s only prior surviving cub, Tai Shan, a few weeks after he was born in 2005, said Mei will likely stay with the newborn for the first few weeks and probably won’t even eat.

She has been tucking the cub under her arm or chin to keep it warm, Thompson said. Gradually, as the cub gets stronger, Mei will leave it for brief periods and venture outside the den for food.

The panda house has been closed for the next several weeks.

At some point, the keepers will try closing the door to the den briefly so Mei can’t get back in. And if she doesn’t mind, someone will slip in the back door to the den, grab the cub, give it a quick physical exam, and return it.

Until then, the keepers must watch, and listen, mostly via the panda cam, from a few doors down. They said they can hear Tian Tian’s loud munching without the aid of electronics.

Keeper Juan Rodriguez, 36, who was scheduled for the overnight shift Tuesday into Wednesday, said they will make sure Mei remains attentive.

“If we see that she is spending time away from the cub for a prolonged period of time, especially if the cub is vocalizing and she’s not responding to it,” that will get his attention, he said.

Another keeper, Marty Dearie, 37, said from the panda house Tuesday: “We want to have a keeper here so that if something were to happen overnight . . . there’s always somebody here with that animal experience.”

“We have a really . . . awesome group of camera watchers” in a control room in the panda house, he said. “But they’re not trained animal people. . . . So we want to have somebody in the building, so if they have a question .8. . they can get one of us . . . to come out, take a look.”

Thus far, he said, Mei Xiang has doted on the cub: “She’s doing everything she’s supposed to be doing.”

He said she has built a massive nest of shredded bamboo that partly obscures her actions. “It’s very difficult to see anything,” he said. Everyone’s like, ‘Have you seen it? Have you seen it?’ We’re like, ‘Maybe.’ ”

“But the cub sounds really healthy, really strong,” he said. “We have heard what sounds like nursing.”

“Our vets . . . said if the cub hadn’t eaten by now it would be in trouble,” he added, “and the fact that it’s still so energetic and healthy-sounding, it’s got to be getting food.”

As for Tian Tian, the panda father, Dearie said he may be aware that the cub has been born, because “that cub is making a lot of noise.”

But male pandas have little to do with their cubs.

“His job is to breed with the females, and then he moves on,” Dearie said. “He’s eating his bamboo. He’s taking his naps. He’s doing the things he should be doing.”

Tian Tian did express some irritation when he was awakened early Monday by the fuss in the house over the cub.

He “honked” with displeasure, Dearie said, as if to indicate: “Who woke me up at 4 o’clock in the morning?”