SAN DIEGO - A giant panda at the San Diego Zoo is showing his age with slow and plodding movements that keepers believe are signals he may be more vulnerable to illness.
Shi Shi's death isn't imminent, but zoo officials say they are preparing for the day he may be euthanized because of his advanced age, estimated to be in his early 20s.
''There are people who think that zoo animals should never die, but you have to prepare people for the inevitable,'' Donald G. Lindburg, head of the zoo's panda team, said Monday. ''Animals of this age may suddenly develop a health crisis. We aren't expecting that, but we have to be prepared.''
Shi Shi has had health problems since villagers in China found him in a coma with severe facial and abdominal injuries in 1992.
Shi Shi came to San Diego in 1996 on loan from China, along with female Bai Yun. He has had corrective dental surgery several times and is being treated for gastrointestinal problems and hypertension.
Shi Shi is the father of the zoo's star attraction, the panda cub Hua Mei, whose first birthday is Aug. 21 and is the first giant panda born in captivity in the Western Hemisphere in the past 10 years.
Keepers were unable to get Shi Shi and the cub's mother, Bai Yun, to mate and resorted to artificial insemination. A second artificial insemination is planned for April.
There are no signs that Shi Shi is suffering and zoo officials will only consider putting him to sleep if his quality of life deteriorates, Lindburg said.
Last year, the National Zoo in Washington, D.C., euthanized the giant panda Hsing-Hsing, who was suffering from kidney disease, severe arthritis and was nearly blind.