Alan, a 43-year-old Sumatran orangutan, died Friday at Zoo Atlanta.

He was the oldest male Sumatran orangutan living in a zoo in North America.

The Animal Management and Veterinary Teams at Zoo Atlanta had been monitoring Alan during recent days for symptoms of decline, including loss of appetite and lethargy, although his official cause of death is not yet known. In addition to his advanced age, Alan was suffering from heart disease. Orangutans are considered geriatric after the age of about 35 years.

“The Zoo Atlanta family is saddened by Alan’s passing. While we knew that he was in his golden years, it’s never easy to lose such an extraordinary Zoo family member,” said Raymond B. King, President and CEO in a press release. “Like his fellow great apes, Alan taught us much about orangutans simply by being an orangutan, and his contributions are many, both to us and to the members and guests who were inspired by him.”

Born May 3, 1971, at the Saint Louis Zoo, Alan arrived at Zoo Atlanta in October 1989. He was known for his impressive size, thick dreadlocked hair and fondness for shiny objects. He was famous throughout the zoo for his frequent long call, a deep booming vocalization used by adult male orangutans to warn other males or to impress females. Years ago, Alan was bestowed with the title of “most genetically valuable male” by the Orangutan Species Survival Plan.

But despite numerous associations with female orangutans, including his most recent companion, 44-year-old Biji, Alan had no offspring.

Zoo Atlanta is home to North America’s largest collection of orangutans. Lori Perkins, the zoo’s vice president of collections, is the national chair of the Orangutan SSP (species survival plan), which seeks to maintain a self-sustaining, genetically diverse population within North American zoos.

Sumatran orangutans are critically endangered, with fewer than 7,000 individuals believed to remain in the wild. Wild populations have declined drastically in recent years as a result of habitat conversion to palm oil plantations, over-harvesting of timber, and human encroachment. Experts predict that the species could be extinct in the wild within 10 years without targeted conservation efforts.

As is the case with all animal deaths regardless of age, a necropsy will be performed through the zoo’s partnership with the University of Georgia Zoo and Exotic Animal Pathology Service in the College of Veterinary Medicine.