Drum roll . . . The giant panda cub is a boy — and its father is Tian Tian.
The National Zoo said Friday that the cub born there last Saturday was doing well.
The other panda cub, also a boy and with the same father, died Wednesday. Officials said an initial necropsy showed that the cub had inhaled some food product, which led to pneumonia.
The zoo’s female adult giant panda, Mei Xiang, was artificially inseminated twice this year — on April 26 and 27 — with semen collected from the zoo’s male giant panda, Tian Tian, and from a male at a research center in Wolong, China.
The Wolong panda, Hui Hui, was picked because he was a good genetic match for Mei Xiang, the zoo has said. The sample from Hui Hui was frozen and flown from China to the zoo’s cryopreservation bank.
The zoo used DNA tests and swabs from the cubs’ mouths to determine their sex and figure out which male sired the cubs, which were not identical twins.
It has been a whirlwind nine days at the National Zoo after experts realized that Mei Xiang was pregnant Aug. 19. She delivered the cubs Aug. 22, and the smaller one died Wednesday afternoon after a six-hour effort by zookeepers to save it.
Officials had used a bottle and a tube to feed the smaller panda cub at various points.
On Friday, the zoo’s chief veterinarian, Don Neiffer, said the cub could have inhaled food during one of the bottle feedings. Experts had also resorted to tube feeding, inserting a tube down the cub’s throat so food could be delivered to its stomach. The cub could have inhaled food at that point as well, Neiffer said.
“I’m sure the difficulty in breathing existed for the cub based on the degree of lung damage that we noted . . . during necropsy,” he said. “The ability for this cub to return to normal health was highly unlikely to impossible.”
Zoo officials said they have been saddened by the death of the cub but are also watching — with hope — the surviving cub as he continues to do well, with a 16 percent weight gain. “We’re ecstatic about that,” Neiffer said.
The zoo said no decision has been made on when the cub will be named. The zoo’s female cub, Bao Bao, was named 100 days after her birth, and the zoo may or may not do the same with the newborn cub.
The newborn will probably make its first public appearance in January, said Pamela Baker-Masson, a zoo spokeswoman.
On Friday, Neiffer said of the deceased cub, “My feeling is that the reason this cub declined is because of complications associated with us hand-rearing it, providing milk either through the nipple or the stomach tube.”
The hand-rearing and swapping of the cubs in and out of their mother’s care was necessary, he said, and has worked well for giant panda cubs in captivity in China.
“If we had not done anything, there was a real chance that neither cub would survive,” Neiffer said.
The complications could have happened to either cub, Neiffer said, as both were hand-fed at different times.
“As the [smaller one] got weaker, looking at the videos we have, there is some feeling that Mei Xiang knew something was going on,” he said. “There was never any evidence that she was preferring one cub over the other.
“We knew going into this that there was potential for the complication that occurred,” he said. “We certainly are going to go back . . . and look at is there anything we would do different? What we wouldn’t do different is the choice that we made.”
Mei Xiang is not new to motherhood.
She gave birth to daughter Bao Bao, whose father is Tian Tian, on Aug. 23, 2013. She also delivered a stillborn cub the next day.
That year, Mei Xiang had been inseminated with sperm from Tian Tian and with some shipped from a giant panda at the San Diego Zoo, Gao Gao.
She also gave birth to a son, Tai Shan, on July 9, 2005.
Zoo experts have said it is hard to determine visually the sex of a cub because the reproductive organs are not fully developed, so veterinarians examine chromosomes. Females have two X chromosomes, and males have an X and a Y chromosome.
The birth of the latest set of cubs has been a closely watched event as the news has unfolded around the world. It was only the third time that giant panda twins had been born in the United States.
One of the cubs was born at 5:35 p.m. last Saturday, weighing about three ounces. To zookeepers’ surprise, a larger twin was born at 10:07 p.m. Saturday, weighing 4.8 ounces, the zoo said.
Keepers had been switching the cubs as often as they could, giving one to Mei Xiang while caring for the other in a special incubator. Then, at an opportune time, they would swap the animals.
This gave each cub time with its mother and allowed her to focus on them individually. Zoo officials have said that often, when twin cubs are born, the mother is able to care for only one, and the other dies.
But it proved hard to make the switches. The smaller cub wound up spending less time with its mother and more time being cared for by the keepers.
Wednesday, after keepers retrieved it from Mei Xiang, it went into decline and died at 2:05 p.m.
Neiffer said the necropsy did not immediately show whether any food substances were still in the cub’s lungs. There was some milk found in its trachea.
Officials said the cub’s lungs looked “angry” and inflamed when they were examined during the necropsy.
Neiffer also said the zoo did not want to raise one of the cubs completely away from its mother. The plan was always to continue swapping the cubs back and forth with Mei Xiang to maximize her bonding with them.
Officials said they were not sure exactly when the dead cub inhaled the milk product, but the zoo staff noticed at one point that the cub had regurgitated some food.
“At some point, Mom would more than likely do what they do in the wild. . . . She would have made a choice,” Neiffer said. “They don’t generally raise both of them.”
“Honestly, we didn’t have a choice,” he said. “What we did was the most appropriate thing, considering the health of both cubs.”