Gao Gao, one of the San Diego Zoo's three giant pandas, was recovering Wednesday from surgery to remove his right testicle because of the presence of a tumor.
The one-hour procedure Tuesday was a success, and veterinarians were hopeful Gao Gao would make a full recovery, zoo officials said.
"He's doing fine," zoo spokeswoman Jenny Mehlow said. "He's just sleeping it off. He's sleeping a lot."
The popular panda will likely be out of public view for the remainder of the month, she said.
The Ministry of Forestry for the People's Republic of China was informed about Gao Gao's health and gave approval for the surgery. All of the zoo's pandas are on loan from China.
Gao Gao is estimated to be about 24 years old and is the father to five panda cubs born at the San Diego Zoo. It was unclear if he would continue to be part of the panda breeding population.
An ultrasound and biopsies revealed that Gao Gao had the tumor called a seminoma, officials said. The tumor is cancerous, but seminomas are typically not aggressive and generally do not metastasize. He was being treated with analgesics and nonsteroidal anti-inflammatory medication.
Gao Gao was born in the wild and brought to a rescue center in China in 1992 with bite wounds on his ear. He came to San Diego from China's Wolong Panda Conservation Center in 2003. Gao Gao fathered five of the six zoo cubs born to Bai Yun, who is 22 years old.
The panda parents share the Panda Trek exhibit with their cub Xiao Liwu, who turns 2 in July.