Cupid, the Toledo Zoo's veteran - and aged - male hippopotamus, was euthanized Monday night after it collapsed, apparently because of an age-related illness, zoo officials said.
Cupid was not standing and would not get up when a keeper tried to let it in for the night, Andi Norman, zoo spokesman, said.
The hippo had shown no previous signs of ill health, Ms. Norman said. A necropsy will be performed.
Cupid, an estimated 49 years old, was captured in the wild of Africa as a calf in August, 1955, when it was brought to the Toledo Zoo.
The average maximum age of hippos in the wild is at least a decade younger, zoo officials said.
Cupid sired 14 offspring - 13 with Bubbles, also approximately 49 years old, and one with Emma, nearly 8. Six of the seven surviving progeny were transferred to other facilities. The other, Herbie, nearly 3, is on exhibit in the zoo's Hippoquarium, with Bubbles and Emma.