. >> he fathered three b cubsn at the national zoo.t 21, he is consideredn older bear and vets have to perform routine check ups to make sure he stays healthy. >> you might equate him to a human entering retierement stag of life. >> the zoo invited us to watch him get hisnnual cardiac ultrasound. this is the first time he had visitors for this procedure so i was instructed not to speak in case id start him. >> being able to evaluate the heart function in an awake animal makes it more natural situation so we can get better formation that way. him an tian's keepers fed honey water to get him to sit still while dr. rosenthal recorded images of his shheart. worked with him since he arrived at the zoo in 2000 and they formed a special bond. >> it's every day interacting with the pandas, training with them, creating the trust. it pays off. >> he likes the attention. usually people focus on the pregnancies or potential pregnancies, and as a cub, he's a fan tfavorite. tian tian is a sweetheart who makes even the tough job fun. >> he is the bes