Giant panda Mei Xiang and her surving and thriving cub in the Smithsonian's National Zoo in Washington in this photo taken on Aug 28, 2015. The cub was born on Aug 22 and was announced on Friday to be a male. Courtesy of the Smithsonian's National Zoo

The surviving and thriving giant panda cub born to Mei Xiang at the Smithsonian’s National Zoo last week is male and his father is Tian Tian, the zoo announced on Friday.

Nancy Rotzel McInerney, laboratory manager of the Smithsonian Conservation Biology Institute’s (SCBI) Center for Conservation and Evolutionary Genetics, also confirmed that the the cub who died on Wednesday afternoon was also a male and sired by Tian Tian at the zoo. The twin cubs born nearly five hours apart on Aug 22, were fraternal twins, meaning they came from two different eggs.

Rob Fleischer, head of the center, said the genetic procedure of determining the gender and father started on Monday. To determine gender, scientists at the zoo sequenced a short fragment of the zinc finger protein gene. The method was developed by SCBI scientists and veterinarians and previously determined to reliably identify the sex of pandas, according to the zoo.

“What we have learned will greatly add to our body of knowledge about artificial inseminations in pandas,” Fleischer said. “Determining the pedigree relationships of a cub is a key aspect of helping to maintain a genetically diverse population. Our ability to assess the cub’s lineage will help our colleagues ensure that he finds a suitable mate.”

Don Neiffer, chief veterinarian at the zoo, said the surviving cub weighed 167 grams at 1:40am on Friday, an increase of 27 grams in 42 hours. “We are ecstatic about that,” he said.

Neiffer said that based on an autopsy so far that the most likely cause of death of the other panda cub was complications from food getting into its respiratory system resulting in pneumonia.

The smaller cub was with mother Mei Xiang from about 2 pm, Tuesday, until Wednesday morning. When the panda team swapped the cubs, they determined that one of them had not increased in weight, appeared weaker and exhibited possible respiratory issues. He died shortly after 2 pm.

Swapping the cubs between the mother and using hand-rearing is a proven method that enables zoo staff to best care for twins if the mother cannot manage two cubs, which was the case with Mei Xiang, according to the zoo. The hand-rearing protocol has been developed from the experience and success of Chinese partners and other zoos.

Mei Xiang has so far given birth to three surviving cubs, two males and one female. Taishan, was born in 2005 and now lives in China for breeding purpose, and Bao Bao, born in 2013, celebrated her second birthday last Sunday.

Both Mei Xiang and Tian Tian are on loan from China. The current agreement, which concludes at the end of this year, will be extended pending further negotiations, according to the zoo.

chenweihua@chinadailyusa.com