Movies sometimes depict gorillas as aggressive brutes. But Pato the silverback doesn’t act much like King Kong.

Like all gorillas, Pato eats bugs and plants. He moves slowly. He lives in a family. Pato walks on all fours toward a squirming infant gorilla, Macibiri. He sits beside her and runs his long fingers through her fur. He’s looking for insects or other things caught in her glossy black coat.

Again, biologist Jean Paul Hirwa is watching. He notices a fresh wound on Pato’s chest, a small red slash. He guesses the wound means Pato was jousting with another male. That sometimes happens when male gorillas are trying to prove who’s boss. Mr. Hirwa tells veterinarians that Pato is hurt.

The vets rarely intervene in gorilla life. Once in a while, they dart a gorilla with antibiotics. But they almost never remove the animals from the mountain. Reuniting gorillas can be difficult.

“Our hospital is the forest,” says Jean Bosco Noheli, a veterinarian for the Gorilla Doctors project. When his team goes into the field, they must carry everything they might need in bags weighing up to 100 pounds. They even tote portable X-ray machines.

Biologists have learned that, over time, gorillas can get used to having people around. That means scientists get a front-row seat for gorilla research. It also means Rwandans can make money from gorilla tourism—if they are very careful.

In Rwanda’s Volcanoes National Park, tour groups are limited to eight people at a time. They can observe the gorillas for only an hour. And they follow rules: No food. No water bottles. (If a curious silverback snatches these items, it risks being exposed to human germs.) And if a gorilla acts aggressive—which is rare—tourists must look down and bend a knee. This shows the gorilla he’s still in charge.

Once, people thought the best way to save animals was to keep local people away from them. But now many believe the opposite. Their new idea is to make locals want to take care of gorillas. People must know that preserving the animals is good for their human communities too.

Each gorilla tour costs $1,500 per person. Rwandans make much more money selling tickets than they would if they had cleared the rain forests and started farms. That’s a win-win-win: win for the rainforest, win for gorillas, and win for people.

Whoever is righteous has regard for the life of his beast. — Proverbs 12:10