This guy was in our back yard at the last house we lived in. The tree he was in was only about 30 feet from the house! There were about 4 adults and a couple of babies with them. We didn’t want to get too close to them as they can get protective of their troop. When you hear the sound of the male calling you know exactly what it is. Some books I have read say you can only hear them 1 km away and others say 2 km. (each kilometer is about 0.6 miles.) I really think it is closer to 2 km. They will wake you up in the mornings if they are close by. They call again at sunset to bring the troop in, they will also call right before it rains or if there is danger in the area.
One day my husband had to walk to town, to get to the center of town from where we were living was probably close to a two-mile walk. Well, on his way to town he notice a bunch of the monkeys sitting in the trees along the road so he decided to stop and just watch them for a while. He was really enjoying the view until I guess the monkeys decided they didn’t like him just standing there staring at them and started to throw fruit at him. At least it wasn’t something else!
Even with where we live at we can still hear them. They make the most interesting sound, you can look it up on youtube. These are the same monkeys that my husband heard the other day right before we felt the earthquake. So, it is a sound to pay attention to when in the rainforest.