WASHINGTON (AP) -- Just a week old, Mei Xiang's tiny cub is beginning to sport the dark markings characteristic of the endangered giant panda.
"When the cub was born its skin was pink, and as it ages it develops those signature markings around its eyes," Carolyn Martin, a spokeswoman for the National Zoo, said Saturday. "It's putting on weight and developing a little round belly."
The darkening tone of skin around the eyes of the cub, the first to be born at the zoo in 16 years, will eventually be replaced with fur.
The zoo's veterinary staff and a consulting specialist from the San Diego Zoo, where two panda cubs have been born and raised, are pleased with the maternal behavior exhibited by Mei Xiang. Although she was artificially inseminated in March, staffers were not sure she was pregnant until the birth occurred July 9.
Mei Xiang appeared surprised herself but did not leave the cub's side for the first five days of its life.
"She left the den and went to another area and had a nice long drink of water. Then she went back and started nurturing it again," Martin said.
The two have been isolated in her den to enable them to bond and reduce the chance of infection. The animals are monitored on closed-circuit video 24 hours a day and can be viewed on the zoo's Web site.
Tian Tian, the cub's father, divides his time between his own indoor den and an outdoor grotto. With the female and cub not expected to be on exhibit for at least three months, Tian Tian is the star of the zoo's Panda House.