Matsu, born at the zoo, underwent treatment and was not exhibited since early December after she began staying primarily indoors.
With Matsu's death, only two bongos remain in Japan, both at Fuji Safari Park in Shizuoka Prefecture.
A bongo believed to be the world's oldest has died at the age of 22 at Higashiyama Zoo in Nagoya, central Japan, zoo officials said Sunday.
The female African antelope named ''Matsu'' was found dead apparently because of old age Sunday morning. The animal's age corresponds to more than 100 years old in human terms, according to zoo officials.
