Ueno Zoo
The Ueno Zoo paired Ling Ling with a female panda named Tong Tong. The two pandas became mates, but were unable to breed successfully and produced no offspring. Tong Tong died in 2000, leaving Ling Ling as the only giant panda at the Ueno Zoo. The zoo had tried unsuccessfully to breed Ling Ling with other pandas since 2001 using artificial insemination. Ling Ling was even sent out of Japan to Mexico three times in an attempt to mate him with other pandas.