Tai Shan eyes up his birthday cake at the Smithsonian National Zoological Park in Washington on July 9, 2009. (UPI Photo/Kevin Dietsch) | License Photo

Tai Shan eyes up his birthday cake at the Smithsonian National Zoological Park in Washington on July 9, 2009. The zoo held an event to celebrate the panda's fourth birthday with a frozen cake made from ice, bamboo, shredded beets and beet juice. (UPI Photo/Kevin Dietsch)

Tai Shan eyes up his birthday cake at the Smithsonian National Zoological Park in Washington on July 9, 2009. The zoo held an event to celebrate the panda's fourth birthday with a frozen cake made from ice, bamboo, shredded beets and beet juice. (UPI Photo/Kevin Dietsch)

At five months-old, Tai Shan, ventured outside for the first time on December 22, 2005 under the close eye of his mother, Mei Xiang. The five-month-old cub explored his outdoor exhibit yard, climbed on fallen trees and wrestled with his mother. (UPI Photo/Jessie Cohen/Smithsonian's National Zoo) | License Photo

Tai Shan, climbs on the rocks in his exhibit after his 12th health exam. (UPI Photo/Jessie Cohen/Smithsonian's National Zoo) | License Photo

At age 4, Tai Shan is on the cusp of adulthood and considered a teenager in "bear years". (UPI Photo/Kevin Dietsch) | License Photo

Tai Shan at 7 month old, plays with mother Mei Xiang, on February 14, 2006. (UPI Photo/Shealah Craighead/White House). | License Photo

The National Zoo's four and a half month old panda cub Tai Shan plays in its habitat, in Washington on November 29, 2005. The panda cub made its media day view today to over 100 members of the press, he will meet a public of sold out ticket holders on December 9, 2005. (UPI Photo/Kevin Dietsch). | License Photo

Handler Laurie Parry, of the National Zoo, holds up .four and a half month old panda cub Tai Shan in it's habitat, in Washington on November 29, 2005. The panda cub made its media day view today to over 100 members of the press, he will meet a public of sold out ticket holders on December 9, 2005. (UPI Photo/Kevin Dietsch).

Handler Laurie Parry, of the National Zoo, holds up .four and a half month old panda cub Tai Shan in it's habitat, in Washington on November 29, 2005. The panda cub made its media day view today to over 100 members of the press, he will meet a public of sold out ticket holders on December 9, 2005. (UPI Photo/Kevin Dietsch).

Tai Shan makes his media day debut at 4 months old to over 100 members of the press. He later met a public of sold out ticket holders on December 9, 2005. (UPI Photo/Kevin Dietsch). | License Photo

The National Zoo's four and a half month old panda cub Tai Shan plays in its habitat, in Washington on November 29, 2005. The panda cub made its media day view today to over 100 members of the press, he will meet a public of sold out ticket holders on December 9, 2005. (UPI Photo/Kevin Dietsch). | License Photo

Laura Bush watches Tai Shan, play. At 7 months old Tai Shan weighed over 33lbs. (UPI Photo/Shealah Craighead/White House). | License Photo