Male gorillas tend to have heart problems, which usually aren't diagnosed until it's too late. They hide any illness. They mask it. And doctors can't tell themselves whether the animals are sick until it is too late, because so little is known about gorilla hearts that doctors don't know what is normal and what isn't. They are trying to learn more, but progress is slow.
Silverback gorillas are terrible patients, and turn every trip to the doctor into a production.
Take Gus , for example. He is 15 years old, and weighs 370 pounds. Instead, doctors have to shoot him with a dart to knock him out. And he runs around, he screams. Gus had his visit to the doctor on Saturday.