Howler monkeys can grow to attain a length of 22-36 inches, excluding the tail which can be as long as the body, and may weigh anywhere between 10-20 lbs. These monkeys live in groups of 10-20 individuals which are known as ‘troops’. Male howlers lead the troops and resort to howling to defend their territory against other groups. The practice of howling is usually at its peak at dawn and dusk. Howler monkeys have an average lifespan of 15-20 years in the wild.
Howler monkeys (genus Alouatta) belong to the Atelidae family of New World monkeys, which also has spider monkeys, woolly monkeys, and woolly spider monkeys to its credit. As of today, as many as 15 species of howler monkeys have been identified.
While the Coiba Island howler is usually considered a separate species, some sources suggest that it’s a subspecies of the mantled howler. Similarly, some sources consider the ursine howler a subspecies of the Venezuelan red howler and tag its scientific name as Alouatta seniculus arctoidea.
Interesting Facts about the Howler Monkeys
✦ According to the Guinness Book of World Records, the howler monkey is the loudest land animal in the world with a howl that can be heard as far as 3 miles away. The species is able to make the loud noise because of its large throat and specialized vocal cords.
✦ The howler species is not just the loudest, but also one of the laziest members of the animal kingdom; second only to the sloth. On an average, these arboreal monkeys spend around 80 percent of their time resting on treetops.
✦ The howler monkeys are the only folivores (herbivore specialized in eating leaves) among the New World monkeys. Other than leaves, they also feed on fruits, flowers, and even buds at times.
✦ These monkeys have a highly developed sense of smell–courtesy sensory hair in their nostrils–such that they can easily smell their food from a distance of 1-2 miles.
✦ Both, males and females of this species have trichromatic color vision, which is believed to be an evolutionary advantage meant to help them choose the best leaves to feed on.
✦ These monkeys have a prehensile tail., i.e., a tail adapted to facilitate grasping and/or holding objects, which works as an extra arm and helps them pluck leaves and flowers.
✦ The tail of the howler monkeys, which might be twice the length of their body at times, is sturdy enough to bear their weight, and therefore, they use it to hang upside down on the trees while feeding.
✦ The Guatemalan black howler is the largest of the 15 recognized howler species, measuring around 20-25 inches in length and weighing up to 25 lbs.
✦ In what can be dubbed as an unusual behavior for a non-primate species, the mantled howler uses sticks as tools to drive away the intruders from its territory.
✦ In black howler monkeys, only the male members are actually black in color. The females, on the other hand, are pale yellowish-brown.
Most of the howler monkey species are found in abundance in the wild and are thus enlisted as Least Concern species by the International Union for Conservation of Nature (IUCN). This is a little surprising as these monkeys are not just hunted extensively for their meat, but are also caught and kept in captivity. Though they don’t make good pets, a considerable number of howlers are exported as exotic pets to different parts of the world. Like other rainforest animals, even howler monkeys are threatened by habitat loss due to rampant deforestation.
All these factors together have resulted in a significant decline in their population. The Maranhão Red-handed howler and Guatemalan black howler have now been enlisted as Endangered species by the IUCN, while the Mexican howler (Alouatta palliata mexicana) and Northern brown howler (Alouatta guariba guariba)–the subspecies of the mantled howler and brown howler–have been declared Critically Endangered, with only a few individuals left in the wild.
Even though these monkeys make a lot of noise, it is very difficult to catch a glimpse of them in the wild as they seldom leave the trees, and prefer to spend most of their day idle. On an average, howler monkeys only travel for a distance of 400 meters a day. If you are lucky enough, you might come across a few howlers on the dense tree tops of the rainforests; the chances are pretty rare though.