Howler monkeys are amazing. They make a guttural hoot or roar that is so deep and so loud that it sounds like it should be coming from a gorilla, not a small, agile animal. If you have not heard one, imagine the sound of the bark from the largest dog, and multiply that sound by about 5 times. That is the sound of one howler monkey.
They usually travel in groups of about 6 monkeys. They can be heard more than a km away. If several groups are in the area, it sounds like the forest is coming alive and roaring.
You do not have to walk deep into the forest to hear howler monkeys. You can hear howlers at times in town. There is a group that lives in the trees on the grounds of the Capitan Suizo resort on the beach in town on the road that leads to Langosta Beach. They can be heard at the Barcelo Resort in the Langosta area of Tamarindo. They travel through the trees that lace from the surrounding forests through town.
It is common to encounter groups of howler monkeys in the trees outside of town. A walk along the beach south from Langosta or a drive outside of town will often enable one to see howlers up in the trees, if you look closely. There are tour operators in Tamarindo who will take you on wildlife viewing river trips that almost always include howler monkey sightings. The guides do a nice job of imitating the roar and hoots of the howlers so that they will make the same sound back.
Howlers are easy to hear, not hard to see, but extremely difficult to photograph well. This photo, taken by my wife, is extraordinary. This howler was looking right at us while eating from a low branch. Usually when one sees howlers, they are high in the trees, and to photograph them you have to shoot up towards the sky. Taking a picture of a dark, black animal against a bright sky in the background usually results in photo that shows only the silhouette of an animal, but does not show the howler's features. I invite you to click on the photo to enlarge it so that you can study his features.
Howlers do not stay still and pose for photos. They hop from branch to branch, and tree to tree. They travel by following each other in their groups, often with a baby hanging on its mother's back. My son recently noticed the spot where they leaped from one tree to the next, and he waited with his video camera and got a video of a monkey flying through the air.