There was this time at Six Flags Safari when the monkeys seemed to be acting strangely. Some people said they saw a monkey with a really menacing look in its eyes. It then led a group of other monkeys to surround a particular area where visitors were walking. They didn't attack but just the sight of so many monkeys being so close and looking so unpredictable was really scary.
There was a legend in a small village about a witch who had six fingers on each hand. She was said to lurk in the forest at night. A group of teenagers decided to test their courage and went into the forest. They saw a figure in the distance. As it got closer, they could see its six - fingered hands. Terrified, they scattered. One of them was chased by the witch until he found a hidden path and escaped. It was a night they would never forget.
A sense of the unknown. Consider 'Fog. Whispers. Unseen danger.' The fog obscures vision, and the whispers suggest something that is not clearly defined. The unseen danger creates a feeling of unease because our imagination can run wild thinking about what that danger might be.
It could be based on some genetic mutations that were rare and people didn't understand in the past. So they made up scary stories about those with six fingers.
The environment of Six Flags Safari can also play a role in making the monkeys scary in a story. It's their territory. If a story is told from the perspective of a visitor who is lost or separated from the group in the safari area where the monkeys live, the monkeys could be seen as a real threat. They know the area better, they can move around more easily in the trees and bushes, and they could potentially corner the visitor, creating a very scary situation.