Scientific name: Alouatta palliata although there are nine recognized species.

Common name: howler monkey, mono (Spanish)

Characteristics: They have an overall size of two to four feet tall or 585-710 mm, with adult males and females weighing approximately 8 to 22 pounds or 4.8 - 7.7 kg. Their color is black with a yellowish or brown color on the lower dorsal area. Scrotum is white, pelage on the tail, head, and arms is short. The monkey lives for up to 20 years. They are gregarious and form groups of 2 - 45 individuals, although they are usually found in groups of 10 - 18 individuals called a troop. They are the loudest animal is the New World and while their howl is now a piercing sound, it can travel for three miles through dense forest.

Male howler monkeys use their big voices to defend their turf. Howls by one troop are answered by other males within earshot. Every-one starts and ends the day by checking out where their nearest competitors are. In this way, they protect the food in their territory. It’s an important job because their diet is made up mostly of leaves—not a particularly nutritious food. Finding young, nutritious leaves is a priority. Fruit and flowers are also valued so it’s crucial that the troop stakes its claim on these treasures when they are found.

Call me sick or crazy, but you will notice that the males are the only ones who have a white part to them. Well, that happens to be their testicles and many of them seem to be well endowed. OK, enough details, but it only seems natural to me that the howling may be the result of banging them on a branch or an ant biting that tender spot. What can I say? It sounds logical to me.

Despite the volume of their howl, it’s disorienting to try to find a troop of loud howler monkeys in the wild. They hang out in the treetops where younger, greener leaves are abundant. However, if you do find yourself in an area where the branches above are rustling and it seems that an unusually large amount of fruit is falling from above or a fine spray of urine rains down on your head, you will know you are close!

Habitat: They are diurnal and can be seen around semi-traveled areas, in evergreen, semi-deciduous, and riparian climax and second-growth forests. Their range is from eastern Mexico to South America, except for the Yucatan Peninsula. Here in Rio Dulce we are fortunate to have the Golden Manteled Howlers and the families are larger because their habitat is extremely limited to a strip of trees and a couple tributaries along the Rio Dulce and growing smaller as people develop the river front properties. There have been attempts to relocate them to other areas before they either kill each other off or run out of living space, but there is enormous government pressure to leave them where they are because they are not indigenous to other areas. There are black howlers at the other end of the lake and other parts of Guatemala, but here we are special! To my knowledge, Tijax and myself are the only ones doing tours of the reserve here on the river. I am not an expert enough to understand this but I feel there is some unbalance that should be taken into consideration.

Food: They feed primarily on the top canopy leaves, fruits, and flowers during the rainy season; in the dry season their diet consists of young shoots.

Can be seen: Early mornings and evenings across the Rio in some inlets and on the lake. During the heat of the day, the monkeys will find a shady tree to hide under and feed. 80% of their day is spent resting and feeding. So unless you have extremely good eyes or are just lucky, your best chance of spotting them is sounding them out before sunrise.

Threats: Loss of habitat, trade, hunted for food in some regions. As I mentioned in "Habitat", my personal opinion after doing the monkey tours for over 8 months, I have noticed that the families are getting extremely large and their territory is relatively small. The gestation period for a female is only four months, but it takes 12 to 18 months to wean a baby. I have noticed a number of 4 to 6 month old monkeys still with their mothers while the mother is nursing a new born. I don't know if this is due to an off balance of male to females, or if there just isn't enough territory for the families to divide.

• Family Atelidae
  • Subfamily Alouattinae
    • A. palliata group
      • Coiba Island Howler, Alouatta coibensis
        • Alouatta coibensis coibensis
        • Azuero Howler Monkey, Alouatta coibensis trabeata
      • Mantled Howler, Alouatta palliata
      • Guatemalan Black Howler, Alouatta pigra
    • A. seniculus group
      • Red-handed Howler, Alouatta belzebul
      • Brown Howler, Alouatta guariba
        • Northern Brown Howler, Alouatta guariba guariba
        • Southern Brown Howler, Alouatta guariba clamitans
      • Guyanan Red Howler, Alouatta macconnelli
      • Amazon Black Howler, Alouatta nigerrima
      • Bolivian Red Howler, Alouatta sara
      • Venezuelan Red Howler, Alouatta seniculus
        • Colombian Red Howler, Alouatta seniculus seniculus
        • Alouatta seniculus arctoidea
        • Juara Red Howler, Alouatta seniculus juara
    • A. caraya group
      • Black Howler, Alouatta caraya
  • Subfamily Atelinae