Sad Goodbye: D.C. Pandas Head Back to China

The Chinese are hoping the pandas will reproduce. To improve the odds, Mei Lan has her pick of boyfriends. Chinese citizens actually are voting for the suitors online.

On one Web site, each bear has its own video and dreamy music. One of them is named "Superman Kobe," and another, "Handsome Yong Yong."

America's fascination with pandas began in 1972, when the Chinese sent President Nixon and the first lady two pandas as a gift, after their historic visit to China. Americans loved the animals, and the phrase "panda diplomacy" was born.

"The giant pandas are the most adorable," Pat Nixon cooed.

Conservationists estimate that there are currently only 1,600 pandas remaining in the wild worldwide and about 200 in captivity. Only three other zoos in the United States have giant pandas -- San Diego, Atlanta and Memphis.

Tai Shan and Mei Lan are now on a mission to save their species -- important work that many wish they could have done here.

ABC News' Stephanie Sy and John Hendren contributed to this report.