Howler Monkey's - Costa Rica's Fascinating Mammals

Biology

One of Nicoya Peninsula’s (and Costa Rica’s) most commonly spotted mammals; the Mantled Howler Monkeys are recognized for their fascinating vocalizations (which can be heard almost 3-4 kilometres away) and incredible response communication patterns. Visitors can often hear their shrill calls around sunrise and sundown. The boisterous species also seem to respond to any other loud noises such as airplanes, thunder, heavy rain and people. Biologists tracking their howling pattern have come to a consensus that it’s used as a mechanism for communication between individual howler monkeys and within their troop. It is also related to territory protection and mate guarding. These sounds are created owing to their enlarged basihyal or hyoid bone, which helps them make loud vocalizations.

Precisely like their name suggests, vocalization and communication forms a vital aspect of the howler monkeys’ social behaviour pattern. In addition to sunrise and sunset, the visitor can hear their cries at regular intervals throughout the day. The main vocal sounds comprise of a loud, deep guttural cry or howl. The noisy primates are widely believed to be the loudest land animals.

Despite their huge size, howler monkeys weigh less than 10 kg which lets them move with more agility, navigating the high trees and hanging from branches by their tails when picking fruit.

The sounds of Howler Monkeys are can be extremely scary for a first-timer in Costa Rica though these sinister sounds betray the fact that these are harmless, peaceful and vegetarian mammals mean no harm and use their vocalizations solely for communicating within their groups. They have a very clever trick up their sleeve though to keep humans who bother them away from their closely guarded groups – they pee innocently and pretend nothing happened. So you really don’t want to stand beneath a howler monkey family next time you go canopy exploring.

There are currently 15 classified species of howler monkeys including Coiba Island howler, Azuero howler, Mantled howler, Ecuadorian howler, Golden-Mantled howler, Mexican howler, Guatemalan black howler, Ursine howler, Red-handed howler, Spix’s Red-handed howler, Brown howler, Jurua red howler, Guyanan red howler, Amazon black howler, Purus red howler, Bilvian red howler, Venezuelan red howler and Maranhao red-handed howler.

A typical howler monkey group comprises several male adults and females, with their infants and juveniles. The juvenile males, once they approach maturity are forced out of their family’s troupe by the alpha male. At this point they appear to be very sad, and wander alone in the jungle. Often they will hang out with a group of humans, as this one did in the photo on the right, who stayed at Anamaya for several days, looking meek and pathetic, apparently hoping to be adopted into our family. They are sometimes known also to tag along with a group of squirrel monkeys (which we don’t have here in this part of Costa Rica) which helps them survive by having those extra eyes looking for danger, and perhaps to help their loneliness. After moving away from their natal group, the males continue to grow in size and strength, and will eventually challenge an alpha male howler of another troupe in battle. If they win, they will often kill the babies of the losing male, or break some of their limbs, leaving them helpless and dying on the jungle floor. These babies are sometimes found by humans and usually end up at Rainsong Wildlife center, where they are nursed back to health and set free.

Female howler monkeys start becoming sexually active at 3 years and usually have their first infant before their fourth year with a gestation period of 6 months. Though the adult male howler monkeys are clearly dominant in rank to their female counterparts, the alpha female in the troupe also has a lot of power within the troupe. An average howler monkey group comprises 11-18 members depending on the region and other conditions.

Physically, the adult monkeys are black with brown or blonde saddles and infants are silver to golden brown and become exceedingly adult-like when they get to about 12 weeks. They have prehensile tails and can live up to 25 years. Howler Monkeys have tiny snouts and round, more wide-set nostrils. They have very perceptive noses and are known to smell food (mainly fruits and nuts) up to 2 kilometers away. Their size ranges from 56 to 92 cm, excluding the tails, which is equally long. In some other species, not found in Costa Rica, the tail is almost five times the actual body length.

Physical fighting among howler monkeys in a group is not very common and they are generally close-knit. However some short duration squabbles can lead to serious injuries. Physical aggression is more pronounced between members of the opposite sex than of the same sex. As stated earlier, group size may vary though the usual ratio is one male to four females.

Howlers are said to be one of the laziest monkeys, since they spend about 80% of their time resting. They generally live to around 20 years old; however, due to a rapid loss of their habitat in many parts of the world, they are finding it increasingly challenging to find the food that they need to survive. They are frequently killed or horribly burned and maimed by the live electric wires running along the roads in most parts of Costa Rica, or in the transformers, which are not required to be shielded. Anamaya was the first hotel in the Southern Nicoya Peninsula to buy and install transformer lead covers to protect them. Their numbers have been greatly reduced in recent years, despite the increase in their habitat, since Costa Rica’s forests are actually expanding (one of the few countries in the world that is doing a good job of re-forestation.) The cause of their dwindling numbers isn’t 100% known, but experts think it’s a combination of too many electric wires, diseases, and they are also known to die off in times of drought.

These intriguing primates are sedentary foragers; i.e., they are primarily leaf eaters but can also be seen feasting on fruits and flowers. Unlike spider monkeys, these aren’t dependent exclusively on fruits and can comfortably survive in home ranges that are comparatively smaller for a primate group of their size. Howler Monkeys are picky eaters and often choose to eat only certain parts of a tree, while moving on to specific parts of another tree to complete their ‘buffet’ style meals. They eat mature leaves, nascent leaves, flowers and petioles of leaves from various trees to give in to their penchant for variety. The sharp primates also appear to base their dietary choices on the amount of protein, fiber, alkaloid and tannin levels contained in the plant. In short, they try to optimize their protein and amino acids intake but minimize the consumption of fiber and secondary compounds.

While they are rarely aggressive with humans, howler monkeys do not take too well to captivity and are generally of an ill tempered disposition. However, the black howler species is a relatively gentle animal and is a common pet monkey owing to its amiable nature vis-a-vis the capuchin monkey, who displays more aggressive characteristics in communicating with humans.

Where To Spot Them

Howlers live in the canopies of lowlands and montane forests and rarely descend to the ground, preferring to swing through canopies for movement within their habitat. In Costa Rica, among other places, they are commonly spotted in all the coastal regions. They are common enough that you’re almost guaranteed to see them at Anamaya sometime during a week here, and you can certainly hear them every morning and night. They howl like crazy at dusk, and also just before a rainstorm. Some people say their howling brings the rain.

Howler Monkeys can also be spotted in large numbers at the Cabo Blanco Reserve just south of Montezuma and Malpais, encompassing the southern tip of the peninsula. Though the park is inaccessible from the west side from Malpais, visitors can use the road that winds through east of Montezuma along Cabuya en-route to the park’s entrance. Visitors wanting to know more about howler monkeys here can access the ranger station that offers information about the reserve’s biodiversity and nature trails. It is best to arrive early to ensure you get enough time to explore.

Our guests can wake up to the trademark cries/sounds of the howler monkeys. They can be spotted swaying on canopies around the resort and at times slyly make their way into the property. The trademark sounds of the howler monkeys complete the experience of staying in the midst of a rainforest wilderness to guests here. Visitors can also opt for a wildlife spotting tour around Montezuma’s famous national parks with the help of expert and knowledgeable guides to view the howler monkeys closely along with other intriguing wildlife creatures of Costa Rica.