Uganda's oldest captive chimpanzee turned 43 on Wednesday with a banana cake and "regular love and grooming" from his female companions, his keepers said.
Zakayo, who was taken into captivity after being attacked by poachers, was presented with a specially baked banana cake, which he had been trained to cut with a wooden knife, but instead he chose to grab it with his hands, delighting hordes of school children.
The 67kg alpha male was brought into captivity in 1972 after his group was attacked by poachers in Uganda's south-west. When he first arrived at the centre, which at the time was the Entebbe Zoo, he was housed in a small cage along with four other chimps and visitors were able to offer him cigarettes and alcohol.
The former zoo has now been transformed into the Wildlife Education Centre - a voluntary organisation that rescues animals orphaned or confiscated by poachers - and the animals have their own small island similar to their natural forest habitat.
Graying and with deep wrinkles on his cheeks, Zakayo, who heads a group of 11 rescued chimps at the centre, has become a favourite with the centre's visitors. Over the decades, he has fathered eight children and adopted many young orphaned chimps introduced to his group.
The average life span of chimps in the wild is between 40 and 50 years, officials at the centre say.
"He gets regular love and grooming from his wives, care and food from the keepers and respect from the rest of his group," said Peace Nakitto, a conservation educator at the centre. "The guy has a stress-free life, which I think is why he's lived so long."