Twin Panda Cubs Born at National Zoo Appear Healthy and Strong

— -- The new additions to the family of giant pandas at the Smithsonian's National Zoo in Washington, D.C. appeared healthy a day after the zoo's adult female, Mei Xiang, gave birth to twin cubs.

The cubs were born a few hours apart Saturday, said Dr. Don Neiffer, a veterinarian at the National Zoo. He said zookeepers won't be certain of the twins' chances of survival until both cubs begin walking.

One cub, believed to be the second-born, weighed in at 132.4 grams, said Neiffer. The second cub is smaller, weighing 86.3 grams, but appeared strong, he said.

Veterinarians were "ecstatic that things are going great," added Neiffer.

Giant pandas give birth to twins about 50 percent of the time, said Neiffer. This is the third time a giant panda living in the U.S. has given birth to twins.

For now, the cubs will alternate spending time with Mei Xiang. When away from its mother, the other cub will be monitored in an incubator.

It may take three to four weeks to determine the cubs' genders and fathers, said Neiffer. Mei Xiang was artificially inseminated with sperm from the zoo's male panda, Tian Tian, and a panda named Hui Hui from China, which was determined to be one of the best genetic matches.

Almost exactly two years before the birth of her twins, Mei Xiang gave birth to a cub named Bao Bao, which will celebrate her second birthday today with a frozen fruitsicle cake made of honey, apple juice, apple sauce, bamboo, carrots and beet juice.