Why It Takes a DNA Test to Determine a Panda Cub’s Sex

The National Zoo announces the 6-week-old giant panda is a boy

Male Panda Cub
It's a boy! DNA taken from a cheek swab of the 3.6-pound giant panda cub confirms the animal's sex. National Zoo

This morning via YouTube, the National Zoo announced the six-week-old giant panda cub is a male. "It's another boy," announced the Zoo's panda keepers Marty Dearie and Nicole MacCorkle. The two unwrapped a painting that was handcrafted by the panda cub's father, the 23-year-old Tian Tian, who can be seen in the video painting canvases first with a pink hue and then with blue.

It turns out, it's hard to sex a panda cub because external genitalia doesn't appear until they are several months old. "Outwardly, male and female cubs appear similar at birth, so a genetic test was the most accurate way to determine the cub’s sex," says the Zoo's Michael Brown-Palsgrove, curator of Asia Trail. Veterinarians examined the cub on September 19 and collected a cheek swab, which was analyzed at the Zoo's Center for Conservation Genomics.

Scientists sequenced a short fragment of the zinc finger protein gene, which is present with slightly different DNA sequences in both of the X and Y chromosomes. With the results in, says Brown-Palsgrove, "the swab sample taken by the Zoo’s veterinarians has both sequences present—confirming that the cub is male."

The cub is now 3.6 pounds and measures 14 inches from his nose to the tip of his tail and his fat, little tummy is a nice 12.5 inches round. He's starting to open his eyes and visitors can catch frequent views of the cub cradled in his mother's arms on the Zoo's panda cams, which are simply nothing short of adorable.

Mother Mei Xiang, who turned 22 on July 22, is the second oldest giant panda in the world to give birth (and the oldest one in the United States); her previous surviving offspring Tai Shan (born in 2005) Bao Bao (2013) and Bei Ben (2015) are all now living at the Chengdu Panda Base in Sichuan, China. The new cub is hailed as the first product of an artificial insemination using only frozen sperm. Mei Xiang was inseminated with Tian Tian's sperm on March 22 and the fetus was confirmed by ultrasound on August 14 and on August 17. The cub was born four days later.

Why It Takes a DNA Test to Determine a Panda Cub's Sex
A blue painting executed by Tian Tian, the 23-year-old male giant panda, revealed the news via a YouTube video this morning. National Zoo

Says panda keeper Dearie, "I was secretly hoping for a boy, so I'm pretty excited about it. Hopefully this cub will be as much as fun as Bei. Because he was an absolute blast."

The new cub's father, the 23-year-old male Tian Tian can be seen in the video manipulating his paintbrush through the bars of his enclosure to create the work of art that features heavy brush strokes in cerulean and sky blue. Asked about the giant panda's artistic influences, curator Brown-Palsgrove noted his exposure to other artists is limited because Tian doesn't get out much: "From our perspective, he appears to lean towards abstract expressionism."

The National Zoo is open with special ticketing requirements due to the global pandamic. The Giant Panda Habitat is closed to give Mei Xiang and her cub the quiet they require. The Asia Trail, which includes views of Tian Tian's outdoor yard, is temporarily closed for repaving of the walkways.