Koga weighs around 180 kilos and is one of the strongest animals at the Buffalo Zoo in New York. Every two years, he is anesthetized so his teeth, muscles, joints and, above all, his heart can be checked. Heart disease is the leading cause of death in gorillas.

Photographer Christian Dobosiewicz documented the procedure and noticed something no one expected. While the medical team examined his heart, Koga stretched out his enormous hand and held that of a nearby nurse. He held it like that, silently, throughout the checkup.

“It is a huge process that requires a huge team”, Dobosiewicz explained. “It can be tense at first, but as soon as we saw his hand, everything changed.” Koga arrived at the zoo in 2007 and, according to the photographer himself, has always behaved like the protector of his group. Western lowland gorillas are critically endangered, with their population declining by more than 60% in 25 years.

