ATLANTA -- Zoo Atlanta has lost a long-time member of its ape family, officials announced. On Monday, Chantek, a 39-year-old male orangutan, died from health complications.

"Chantek will be deeply missed by by his family here at Zoo Atlanta," said Hayley Murphy, the vice president of Animal Divisions. "He had such a unique and engaging personality and special ways of relating to and communicating with those who knew him best."

The orangutan's cause of death hasn't been determined, but zoo officials said the ape had been treated for progressive heart disease. Zoo Atlanta announced in 2016 that animal care teams had begun a medical regimen to treat Chantek's symptoms of heart disease and even underwent a voluntary echocardiogram.

Cardiac disease, zoo officials said, is the primary cause of death among great apes in zoological populations.

Chantek was born on Dec. 17, 1977 and arrived to Atlanta's zoo 20 years later. The ape was well-known for his knowledge of American Sign Language, which he learned before arriving to Zoo Atlanta. In addition to forming bonds with his human caregivers, he formed close relationships with Zoo Atlanta's other orangutans, Madu, 34, Demadi, 10, Remy, 6 and Keju, 2.

According to Zoo Atlanta, at 39, Chantek was one of the oldest living male orangutans within the North American population. Orangutans are considered "geriatric" after age 35.

Officials will perform a necropsy to determine an exact cause of death. Preliminary results should be available in a few weeks.