Common Name: Mantled Howler Monkey
Latin Name: Alouatta palliata
Family: Atelidae

Range: southern Mexico to northwestern South America

Coloration and Morphology: Mantled howlers are black with either brown or orange fur on their sides, which give them the name “mantled”. Babies are lighter in color and darken as they age. Males are slightly larger than females, and on average howlers’ bodies are 56-92 cm with equally long tails. They have prehensile tails, meaning that they can grasp with their tails. They use their tails to support their body weight when they hang in trees and also to help them move or balance.

Fig. 1: Baby Mantled Howler Monkey foraging in the canopy in La Selva, Costa Rica.

Voice: Howler Monkeys are considered to be one of the loudest land animals in the world. Their distinctive “howl” is a deep, guttural yell that the males make in order to communicate location and claim their territory.

Reproductive cycle: Males reach maturity when they are about 3 ½ years, and females are sexually mature by age 3. The average gestation period for Howler Monkeys is 186 days.

Habitat: Howlers spend most of their lives in the canopy of tropical rainforest trees.

Behavior: Mantled Howlers are unique from other species of Howler because their social groups generally have more than three adult males while others only have three or less. The males are the leaders of the group, and the youngest adult male is the alpha. Social groups are not highly related and juveniles leave their natal groups when they become adults. It is beneficial for these social groups to form because the different individuals can protect each other. Mothers take care of their offspring by carrying them from tree to tree when they are young; they play a significant role as a caregiver.

Diet: Mantled Howlers eat mainly leaves, but will also eat fruit and flowers. Figs and Fig tree leaves are also a part of Howlers’ diets.

Interactions: Mantled Howlers do not have many natural predators, and the main threat to their survival is deforestation. However, they are hunted by jaguars and birds of prey.

Personal Experience: We saw two male Howlers cross the Stone Bridge less than 5 feet from where we were standing. It is clear that they are not afraid of humans. We also heard them making calls throughout the day. Howlers were seen sitting in the tops of trees in groups of less than 15. These monkeys were foraging and resting. We saw a few juveniles that were riding on their mothers, but none that were young enough to have noticeably lighter fur. We saw them hanging by their prehensile tails, and one morphological observation that I made was that there was an area near the end of their tails that had no fur and looked fleshy like the palm of our hand.

Glander, Kenneth E., 1977. “Poison in a monkey’s Garden of Eden”. Natural History, 86: 146-151.
Glander, Kenneth E., 1980. “Reproduction and population growth in free-ranging mantled howling monkeys”. American Journal of Physical Antrhopology, Volume 53, Issue 1, 25-36.
Peetz, Angela, Norconk, Marilyn A., and Warren G. Kinzey, 1992. “Predatation by jaguar on howler monkeys (Alouatta seniculus) in Venezuela”. American Journal of Primatology, Volume 28, Issue 3, 223-228. Viewed on 3-2-12