Fifi, a 49-year-old female chimp, died Friday after a rapid decline in health.
"That is very, very old for a chimp both in captivity and in the wild," said Randi Meyerson, the zoo's curator of mammals. "She lived a good, long life."
Fifi came to the zoo in 1963 at the age of 3 and was a well-liked member of the community with a strong personality, Ms. Meyerson said.
On Thursday she started showing signs that she was stiff and tired. Chief Veterinarian Chris Hanley examined her and started her on medication, which improved her condition and on Friday morning she was moving better and was more active.
By the afternoon, however, she had become disoriented, deteriorated rapidly, and died.
A necropsy revealed possible blood vessel abnormalities in the brain, and further tests are pending to determine a cause of death.
The loss of Fifi leaves just one chimpanzee at the zoo, the 50-year-old male named Harvey.
A large birthday bash was held in January for Harvey and Fifi to celebrate their long lives.
Fifi was one of the oldest female chimps in the North American zoo population.
Regular visitors to the zoo will remember Fifi as the chimp who always carried a toy alligator with her or "asked" spectators to show her their belly buttons.
The alligator toy had belonged to Mickie, and when the chimpanzee died in 2000 Fifi picked it up and never put it down, Ms. Meyerson said.
It was once a green plastic alligator but had over the years become a white bottom half of an alligator. The staff tried to get her a new one, but Fifi preferred the one she had.
Nobody knows where the belly button fascination started, Ms. Meyerson said, but the chimp would solicit people to lift up their shirts so she could see them.
Fifi was a very active animal that enjoyed interacting with the staff, often engaging them in a game of chase, and the guests, especially the children, Ms. Meyerson said.
"She had her own distinct personality and she was a nice animal," she said. "I know the staff that worked closely with her will miss her dearly. It's a sad day."
Fifi and Harvey have been popular animals at the zoo because visitors interact with them and are interested in their behaviors, some of which are similar to humans, Ms. Meyerson said.
The Toledo Zoo plans to work with the chimpanzee Species Survival Plan, which is a cooperative breeding and conservation plan created by the Association of Zoos and Aquariums, to decide the best social situation for Harvey now that he is alone.
Harvey came to the zoo in 1971, but left for a few years to Baltimore in a failed attempt to get him to breed.