STATUS IN THE WILD: Least Concern
RANGE: South America
PHYSICAL FEATURES AND CHARACTERISTICS
Black howler monkeys are one of the few primate species that have sexual dimorphism, which means that the males and females have different coat colors. The males have a black coat, while the females are blonde. Juveniles of both genders will also appear blonde until they reach sexual maturity. These primates have a prehensile tail that has no hair on the bottom side; this helps them grasp onto branches during locomotion. They have five fingers and five toes, which also help when climbing. They typically weigh between fifteen and twenty-two pounds and are around two to three feet in height. The males are usually taller and heavier than the females.
Their upper molars have sharp, shearing crests that are used to grind leaves. Howler monkeys, like all monkeys from the Americas, have nostrils that are far apart and sideways-facing, whereas African monkeys have nostrils that are close together and point in the same direction. Their hyoid bone (Adam’s apple) is enlarged, which restricts some of their arm movement and makes them rely even more on their tail for locomotion.
They are named after their vocalizations and can be heard most often around sunrise. The “dawn chorus” sounds more like roaring than howling and announces the howler’s position to other howlers. This call can be heard up to three miles away. The males have large throats that are specialized, with shell-like vocal chambers that allow their call to be heard far away.
LIFESTYLE AND REPRODUCTION
Male members of the group wake each morning at dawn with a “chorus” that is answered by other males. Since the howlers do not have exclusive territory and share parts of their range with others, this morning call helps them defend, define, and clarify the group’s home range. The weaker troops can identify the strong troops and avoid those areas while looking for food. These troops are usually between ten to twenty monkeys, with more females than males. When two different howler groups meet, they use a lot of energy in howling, leaping, running, and fighting. In order to not waste too much energy, the males spend a lot of time howling to defend their range.
Howlers spend a lot of their day resting. Because they can only extract limited calories from their food, they have to be very cautious about how much energy they use. They do not like to jump from tree to tree and prefer to always have a hand, tail, or foot holding onto a tree as they reach to the next tree. They have been seen linking together hand-to-tail with multiple monkeys in order to make a bridge for the young howler monkeys to cross. Males handle all the disputes and defend the group from various predators. This allows the female to spend more time and energy on reproduction and caring for the young.
Females typically give birth every other year, resulting in one offspring after a one hundred eighty day gestation period. The young will reach sexual maturity around eighteen months of age. Tongue flicking is a ritualized display of sexual solicitation. Their tongue is pink with black bordering, which makes it easy to spot.
Black howler monkeys can be found in southern Brazil, Paraguay, eastern Bolivia, and northern Argentina. Since they do not have to travel far to find leaves, they stay in a small home range for most of their life.
Howler monkeys spend almost all of their time in trees. They can be found in primary, arid deciduous, and broadleaf forests.
These primates are herbivores, mainly consuming tree vines, leaves, flowers, and tropical forest fruits. Howlers mainly eat leaves and greens, and spend little time eating the flowers and fruit since they are less abundant. When available, they will sometimes eat the eggs from birds’ nests. They get all their liquid they need from their fruits and plants; therefore, they are seen drinking little water.