Howler Monkeys

Call of the Wild

The call of howler monkeys is one of the sounds which most defines an experience of Latin American rainforest.  Howler Monkeys have the loudest call of any terrestrial mammal and can be heard 3 miles through dense rainforest. Most commonly we hear them at dawn and at dusk, but we might hear them at other times in the day when they feel the need to define their feeding territory. 

The sound of a howler monkey is a good reflection of the health of an area of lowland rainforest we visit. With body lengths (excluding the tail) ranging from 56 to 92 cm (22 to 36 in), they provide a worthy meal to a hunter. In a good patch of Amazon or some of the more remote Mayan ruins, we might hear three or more troops of howler monkeys filling the airwaves. 

Breeding & Competition 

Howler monkeys don't often fight, but when they do, they can inflict significant injury. They won't attack a human, but they have been known to hurl faeces down at people. 

They live in troops typically of 6 - 15 individuals, consisting of 1 - 3 adult males and several females. Males have enlarged hyoid bones between the jaw and neck. This gives them a powerful appearance, but studies have shown that the larger their hyoid, the smaller their quite visible white testicles. Males with larger hyoids are less likely to share a group with other males. This eliminates mating competition within a troop, but does not guarantee genetic dominance, because females will mate with multiple males inside and outside her home group. 

Food & Intelligence 

Howler monkeys feed largely on leaves as well as fruit, nuts and on rare occasions, bird eggs. Eating leaves demands long hours of rest for digestion. Their reduced dietary range requires less intelligence than more widely omnivorous Capuchins or Spider Monkeys. 

Red, Black, Brown and Mantled 

Howler monkeys are the most widely spread primates in the Neotropics. There are 15 species of howler monkey varying in colour from red to brown to black. In Belize the Guatemalan Black Howler (Alouatta pigra) is locally called a Baboon. Some of our best sightings in Belize - and on our private safaris in the Yucatan of Mexico - can be in forests close to Mayan monuments. 

On our tailor made and small-group Tropical Andes to Amazon journey to Ecuador, it is the richly coloured Red Howler Monkey (Alouatta seniculus) we see and hear. 

Get a Grip 

Howler monkeys (genus Alouatta) are from the family Atelidae, of which Spider Monkeys and Woolly Monkeys are also a part. All Atelidae species have gripping ('prehensile') tails with a palm of thicker flattened skin where it grips. This acts like a fifth limb - an adaptation found only in New World monkeys. 


The biggest threat to all New World Monkeys is the loss of habitat through deforestation. Hunting is a particular threat for Howler monkeys, on account of their size. 

Where Howler Monkeys fare better than other large New World Monkeys, is that their diet primarily of leaves can be fulfilled within a smaller range. Healthy populations can exist in relatively isolated areas, such as the 400 acre Lamanai Mayan complex in Belize. Here they are surrounded by many thousands of acres of land deforested by Mennonite community farms. 

To see what Aqua-Firma has been doing to help New World Monkeys and their habitats in visit: 

  • Black Howler monkey in Belize
  • Red Howler Monkey in the Ecuadorian Amazon


Costa Rica

  • Amazon Red Howler Monkey
  • Howler Monkeys primarily eat leaves


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