Behind the scenes photographs show what it's like to get a closer look at a 181kg gorilla, as it lay unconscious during a physical examination.
Koga, a 34-year-old western lowland gorilla, undergoes a health MOT every other year to make sure everything is in order.
Christan Dobosiewicz, 30, captured the images of Koga who has been at The Buffalo Zoo, in New York, since 2007.
He said: "Koga is a very good father to the other gorillas in our zoo. He gives off mean looks but that's his role as the protector.
"He is really good with keepers and responds well to training sessions and behind the scenes he is always playing with the kids.
"Every couple of years he undergoes a physical examination to make sure he is healthy and well.
"They take a look at his heart to check for heart disease which can be common in these animals, as well as giving the rest of his body, including his teeth, eyes, joints and muscles, a once over.
"It's a big process and takes a big team to ensure everything goes smoothly. He is huge and can be a very dangerous animal, so it can be tense to begin with, but our team are remarkable."
Mr Dobosiewicz added: "It's incredible to see the size of his hands and fingers. I put my hands up against his and it puts a lot of things into perspective."
Mr Dobosiewicz confirmed the examination on Koga went well and he is "as happy and healthy as ever".