This happened to me a few years ago when I was on holiday in Meia Praia, a small town near the beach in Brazil.
My boyfriend and I wanted to go walking through the forest because it was a wonderful sunny day. We started walking early in the morning. While we were walking we listened to a strange sound several times, but we didn´t care about it. As we were nearer the beach which was on the coast of the Island, that sound was stronger. In the middle of our way to the beach, a couple warned us about the wild monkeys which live there, but we didn´t care about it, neither.
When we were just some meters from the beach, we felt that noise behind us and at the same time a big monkey appeared in front of us. It was a harmless animal which made a strong noise because it was afraid of people. Unfortunately, we didn´t know that these species lived there and we could have made him to get annoy.
Since then, we learned to pay attention to the signs of nature.