A 400lb gorilla lies unconscious during a health checkup by vets at The Buffalo Zoo in New York.
Koga, the western lowland, undergoes a 'health MOT' every other year, checking for heart disease as well as the condition of his teeth, eyes, joints and muscles.
Incredible images from the procedure show the 34-year-old silverback clutching a veterinary nurse's hand while hooked up to heart-monitoring equipment.
Koga, the alpha male and 'protector' of his brood, has lived at the zoo since 2007.
Christan Dobosiewicz, who captured the stunning images, 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."
On his health examination, Dobosiewicz added: "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.
"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."
"The team are professional and always on the ball. It's never nerve wracking being in the room with them because I know how amazing they are at their job.
"It's very cool to see it how powerful and strong he is, as well as getting so close to such an interesting animal.
"Everything went well during the examination and Koga is as happy and healthy as ever."
