Ozzie, the world's oldest male gorilla recorded, has died at 61 at Atlanta Zoo, according to the zoo authorities. 

The cause of death has not yet been revealed, and according to the press release, a necropsy will be conducted by the University of Georgia Zoo and Exotic Animal Pathology Service at the College of Veterinary Medicine.

Ozzie began displaying signs of loss of appetite last week, according to a new statement from the zoo. He was then treated by the zoo's veterinary experts for symptoms such as face puffiness, weakness, and an inability to eat or drink fluids.

Raymond Kind, the President and CEO of the zoo called the loss "devastating", adding that “Ozzie’s life’s contributions are indelible, in the generations of individuals he leaves behind in the gorilla population and in the world’s body of knowledge in the care of his species.”

Ozzie was the sole survivor of a generation brought to AtlantaZoo in 1988. In 2009, he became the world's first gorilla to participate in a voluntary blood pressure reading.

According to the news release, he is survived by seven children in the Atlanta Zoo and other children in the US and Canada.

Poaching, habitat degradation, and disease-related population declines have all contributed to the severely endangered status of lowland gorillas. According to the International Union for Conservation of Nature, their populations have fallen by 60 to 90% in some regions of western Africa.