A 28-year-old chimpanzee named Charley died at the Maryland Zoo in Baltimore over the weekend.
Zoo spokeswoman Jane Ballentine said an initial necropsy provided no obvious explanation. The animal's remains have been sent to the Department of Comparative Medicine at Johns Hopkins University for closer examination and tests.
Charley is the third adult chimp to die at the zoo in the past two years. The others were Joe, a male about 35, of peritonitis; and Rusty, 23, a female, of anesthesia complications after severe tonsillitis, said Dr. Ellen Bronson, senior veterinarian. The troop now has one adult male and eight females, including Rosie and Jamba, born at the zoo in 2005 and 2006.
Keepers found Charley in his quarters Saturday morning. They believe he died overnight without showing signs of illness. "Charley had a physical exam earlier in the month, and by all appearances he was healthy and aging normally," Bronson said.
At 28, Charley was approaching the 30-year threshold beyond which chimps are regarded as "geriatric," Bronson said. "He definitely was not young." Chimps in their 30s "can begin to have cardiac and other age-related issues, not unlike middle-aged humans," she said. But a complete cardiac work-up a year ago, including an echocardiogram, revealed no issues.
Charley was brought to Baltimore from the Detroit Zoo in 2003 at the recommendation of the Chimpanzee Species Survival Plan. It was not for breeding; Charley had had a vasectomy because his father was unidentified. The plan was to create a multimale group within the troop, similar to those found in the wild.
And he fit in nicely. He was described as a "good uncle" to some of the younger chimps and a close friend of an 11-year-old male named Kasoje.
"I don't think there is anything unusual" about the zoo's recent chimp deaths, said Rebecca Gullott, mammal curator at the zoo. "The circle of life is what we deal with every day." As for Charley, she said, "He will be fondly remembered by zoo staff, volunteers and guests."