The Smithsonian National Zoo’s four-month-old giant panda Bei Bei was still cute to watch, despite not having a whole lot of energy during his big media debut. (Ashleigh Joplin/The Washington Post)

The little “tank” had been squirming in his den for much of the morning, trying to get his stubby back legs to work and rolling in the bamboo, and when animal keeper Nicole MacCorkle scooped him up, he was tired.

She toted him down a corridor and placed him on a table covered in blue cloth, as news cameras clattered. She weighed him — 17.5 pounds — and looked at his teeth. He took a few steps, fell fast asleep and began to drool.

So went the much-anticipated media debut this week of the National Zoological Park’s 4-month-old giant panda, Bei Bei, who was named by the first ladies of two countries and was described by keepers as “precious” and “beautiful” — and as rugged as a tank.

Born in August, along with his doomed twin brother, Bei Bei has grown into a muscular cub with all four of his canine teeth, wide paws, and sharp claws that have been dulled only a little as he has become more mobile.

But he still is nursing several times a day and has never been outside. His limited eyesight makes him a little jumpy, keepers said Monday during the first of his media appearances this week.

He made other appearances Tuesday and Wednesday and makes his public debut Jan. 16.

For now, Bei Bei resembles a miniature version of the 275-pound bruiser that he will become when he is full grown in about six years. And his thick black and white fur is getting as tough as an adult panda’s.

“The cub’s [fur] are a little softer, but as they grow, their fur gets a little bit more coarse,” said zoo biologist Laurie Thompson, who had spotted Bei Bei’s birth on the night of Aug. 22. “It’s kind of like wool, and that helps keep them warm.”

“The cubs are very dense and heavy,” she said. “They’re not fragile, at all.”

Bei Bei, who first opened his eyes in October, can see better but still not well, Thompson said. “If something is peripheral to him,” it can startle him, she said.

“He can definitely look at us, but he gets spooked a bit by fast movements,” she said.

Thompson said the keepers wanted to wait until he can walk well before they let him go out. She said Bei Bei will probably be allowed out in January or February, depending on the weather.

The keepers said he is big for his age, putting on about a pound a week. “He is bigger than all of our other cubs,” Thompson said.

His hearing is good, and he knows the voices of his keepers. “The most important thing we can do for these animals is make sure that they know when we call, we are the safe place to come to,” said Brandie Smith, the zoo’s associate director for animal care sciences.

The birth of Bei Bei, whose name is pronounced “bay bay” and means “precious treasure,” was only the third time that giant panda twins had been born in the United States. The zoo initially said Bei Bei was the second cub born, but now officials say they are uncertain.

The zoo’s adult male giant panda, Tian Tian, fathered both cubs, after the mother, Mei Xiang, was artificially inseminated in the spring with his semen and that of a panda in China.

Bei Bei has an older sister, Bao Bao, who was born at the zoo Aug. 23, 2013, and still lives there. He also has an older brother, Tai Shan, who was born in 2005 and lives in a panda conservation center in China.

The birth of Bei Bei and his twin, who was never named, posed a delicate problem for the zoo. Panda mothers often have a hard time caring for two cubs, and usually only one survives.

So the zoo tried switching the cubs — leaving one with Mei Xiang while keepers cared for the other. After a time, the keepers would switch the cubs back, so each one got time with Mei Xiang.

But after several days, it suddenly appeared that the smaller twin was seriously sick. During one of the switches, keepers saw that it was lethargic and was having trouble breathing.

The cub, which weighed only three ounces, had contracted pneumonia after inhaling formula it was being fed by keepers, the zoo said later.

Zoo veterinarians placed the cub in an incubator, pumped in oxygen and administered antibiotics, fluids and nutrition. Nothing worked. The cub went into cardiac and respiratory arrest. The veterinarians tried gentle CPR, but at 2 p.m. Aug. 26, the cub died.

The zoo’s staff members were devastated, but they still celebrated the survival of Bei Bei, whose name was selected and announced Sept. 25 by first lady Michelle Obama and the first lady of China, Peng Liyuan.

Keepers said Bei Bei has had most of his shots — he gets stuck in a rear leg — has tasted bamboo leaves and has started playing with his mother. He won’t start eating solid foods until he’s about 6 months old.

Mei Xiang, for her part, “is a phenomenal mother,” zoo keeper MacCorkle said. “She always just amazes us with her patience with him. He’ll be crawling on her. She’s trying to eat. She will very subtly push him away.”

She also still hauls him around by holding the scruff of his neck with her mouth.

Bei Bei’s mobility remains limited. His back legs are still uncoordinated. “He’s just figuring out how to use his back legs,” zoo biologist Thompson said. “He’s a little wobbly on them.”

But giant pandas don’t do much running. Tian Tian, the adult male, runs when he hears thunder, the keepers said, and during the 2011 earthquake on the East Coast, all of the pandas ran.

Bei Bei, as with other giant pandas born at the zoo, will eventually be sent to China, the species’ native land. China owns and leases all giant pandas in U.S. zoos and requires that cubs born in the United States go to China to breed when they are about 4 years old.

“It’s very sad,” Thompson said. “But we know, as keepers that work with pandas, that that’s the case. . . . So you definitely try to . . . not get overly attached. . . . You just kind of get it in your head, ‘No, these cubs are going.’ ”

“You just have to remind yourself,” she said.