The red howler is a fairly large primate, but certainly not the largest in the Amazon Basin. Like other howler species and subspecies, red howlers live their lives well above the forest floor. These animals are very much at home in the canopy and sub-canopy of the rainforest and gallery forests of South America. Due to the species' extensive range, from Venezuela to Argentina, it is found in a wide range of forest types. In areas of the llanos, the red howler is confined to the forests along the edge of streams. These forests are called gallery forests. In the massive basin of the Amazon River, the red howler is found throughout much of the region. The exception is in the large tracks of deforestation that appears to be an unstoppable cancer in much of the basin today. Like all large monkey species, deforestation and hunting pressure has resulted in the disappearance of monkeys in a large part of their historical range. Red howler is no exception in this unfortunate circumstance.
Red howler monkeys are an attractive species with a rich dark reddish coloration. Their troops are not exceptionally large and troops of 10 to 15 appear to be average. Both males and females vocalize, and a troop of 10 howlers can sound as if there is an army of upset monkeys. Typically calling is a means of defining territory, but other loud noises such as thunder, boat motors and guides imitating the call can set a troop into a full chorus. This can occur both day and night, and at night the call of the howler can be an especially eerie sound.
On my many Peruvian Amazon tours  (over 30 trips), I have observed red howlers many times. They are always a delight to observe as they are not nearly as common as the saddle-backed tamarin or squirrel monkey. I have, on occasion been out on a black-water lake in a small excursion boat until the very last hint of light is in the western sky. Frogs and katydids are just beginning to crank up ,and off in the distance the booming call of red howlers is the icing on the cake. It always reminds me of “place”...that I am in the greatest rainforest on the planet waiting for the changing of the guard from diurnal sounds of birds and insects to a slight silence at dusk. And then, the iconic call of howlers. It does not get any better than that!
Naturalist Greg Greer  is a favorite among IE travelers, and has gained a reputation for his friendliness and good humor, along with his incomparable knowledge of natural history. Greg's photos and articles have been widely published in books and magazines, including Georgia Outdoor News, Bird Watcher’s Digest, Alabama Outdoor News, Riversedge and Southern Wildlife.