Giant panda Le Le has died, the Memphis Zoo announced Friday.

The panda, born July 18, 1998, died Wednesday, zoo spokesperson Rebecca Winchester said in an email. His cause of death has yet to be determined as a medical investigation is pending, the zoo said.

"Le Le’s name translates to ‘happy happy,’ and his name perfectly reflected his personality," the zoo said in a statement. "Le Le was a happy bear that enjoyed apples, engaging with enrichment and relaxing while covering himself with freshly shredded bamboo. He had an easy-going personality and was a favorite of all who met and worked with him over the years."

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Le Le had been at the zoo since 2003 and was expected to return to China soon with female panda Ya Ya as a loan agreement ended with the Chinese Association of Zoological Gardens.

The life expectancy of a giant panda in the wild is about 15 years, but in captivity they have lived to be as old as 38. Decades of conservation efforts in the wild and study in captivity saved the giant panda from extinction, increasing its population from fewer than 1,000 at one time to more than 1,800 in the wild and captivity.

The advocacy group In Defense of Animals has applauded the return of the animals, saying they had been suffering in the zoo setting. Zoo officials have said the pandas are healthy and well taken care of, with as much as they want to eat.