Guianan Red Howler, Alouatta macconnelli
GUIANAN RED HOLWER
Alouatta macconnelli
Geographic Distribution and Habitat
The Guianan red howler monkey — also known as the Guyanan red howler — can be found in Guiana, French Guiana, Trinidad, Suriname, east of the Orinoco River in Venezuela, and north of the Amazon River in Brazil. They have also been observed living on the Ilha Tupinambarana, an island in Brazil surrounded by river channels of the Amazon system.
These monkeys are typically found in rainforests near sea levels, dry deciduous forests (forests that experience differences in weather for the four seasons, where trees usually shed their leaves in the winter), gallery forests (narrow strips of land that grow around rivers or streams), and savannas. Though uncommon, they have sometimes been seen living near swamps and in mangrove forests. Though these red howlers can be found in all levels of the forest, and sometimes even travel for brief stretches on the ground floor, they spend the majority of their time in the middle to upper canopy.
The Guianan red howler monkey, or Alouatta macconnelli, is one of nine subspecies of the overarching red howler monkey species. At one point a team of scientists argued that red howlers east of the Trombetas River in Brazil are unique to the ones on the west of the river, and established the eastern howlers as Aloutatta macconnelli. There was another howler species found on the island of Trinidad that was included as a junior synonym of Alouatta macconnelli, but this ruling was changed in 2017.
Size, Weight, and Lifespan
Female Guianan red howler monkeys weigh around 13 pounds (6 kg) with a body length ranging from 18 to 22 inches (46-57 cm), while males are typically around 16.5 pounds (7.5 kg) and 19 to 28 inches (49-72 cm). Despite these size differences, both genders have a comparable range when it comes to tail sizes: 19 to 29.5 inches (49-75 cm).
There is not enough research on the Guianan red howler monkey specifically to be able to accurately discern their average lifespan, but we can look into other howler monkeys to gain a better understanding. Venezuelan and Colombian red howler monkeys are known to live up to 25 years, with some documented cases of various red howlers living past 22 years in captivity.
Appearance
Both male and female Guianan red howler monkeys have a gorgeous, striking orangey auburn coat, aside from the underside of their prehensile tails, which are hairless to provide a stronger grip. Their tails are so strong, they can support the entire weight of the monkey while they hang from a branch, hands-free, to reach food.
Their faces are long and stoic, black with a broad nose and wide, downturned mouth. Their coat frames their black faces with a soft upside-down triangle shape, with their ears poking out on either side and a long beard of fur that finishes with a pointed tip. Males of this species have bigger, more muscular heads, as well as a larger hyoid bone in their neck, which is located around where a human’s Adam’s apple would be.
Diet
A folivorous monkey, meaning their diet mainly consists of leaves, the Guianan red howler monkey usually eats around dusk and dawn. They prefer to eat younger leaves as they are easier to digest and contain more protein and sugar, but they will also eat some fruits and flowers that are in season. Because their diets are mostly leaf-based, their digestive systems are outfitted with specialized acids as well as two enlarged sections in the cecum and colon in which fermentative bacteria are found. Some of the most common plants found in their diet include laurel espada, palo de gallina, Assai palm, black manwood, wild balata, Jamaican cherry fig, and ice-cream-bean. For water, they will often lick leaves after rainfall or travel to the ground to drink from various bodies of water or puddles.
Behavior and Lifestyle
Guianan red howler monkeys are diurnal, meaning they travel and forage during the day and rest at night. They are also arboreal, meaning they spend most of their time within the canopy. Their feeding and foraging time run around sunrise and sunset, but aside from that they are very sedentary creatures, spending over 15 hours a day in a seated position. This is because their nutritiously low folivorous diet requires a good deal of energy to digest.
When they are moving around, usually in search of food, they follow similar routes each day and seldom exceed 600 meters of travel. These patterns can change depending on the environment they are living in, as some locations have fewer, more dispersed food sources. For example, in secondary forest habitats (forests that have since regenerated from human interference), Guianan red howler monkeys use the limited trees as a home base between feeding times and as a sleeping zone at night, then locate a feeding tree within the vicinity, eating from it until it’s nearly depleted (and repeat the process, finding more feeding trees). However, in more abundant forest habitats, groups of these monkeys are able to munch freely on the numerous feeding trees within their home range without risk of running out of resources.
These creatures are slow, intentional movers, using all four limbs to climb and travel, as well as their prehensile tails to hang onto or pull branches. When they reach a gap in the trees, they will extend a limb and do a leaping movement, while still maintaining a grip on the initial branch with their tail or back feet until they are properly within grasp of the branch they are moving towards. When climbing down trees, they face the ground while climbing on all fours, using their tails to keep themselves steady.
While eating, these monkeys will sometimes hang upside down, using their prehensile tails to hang onto a tree branch.
A fun invite for your next pool party, Guianan red howler monkeys have been observed swimming distances over 650 feet (200m).
Though folivorous, these monkeys love to raid termite nests for a termite snack! Some sources suggest that they even eat parts of the nests themselves.
Being very social animals, these monkeys rely heavily on their groups, which range from 3-10 individuals. There is a hierarchical power dynamic, with each group being led by one dominant adult male; the rest of the group consists of 1-2 subadult males and females and their young. Combative behavior is rare and, if it does occur, it’s usually among the same sexes. For example, mature outsider males sometimes challenge the dominant male of a group in the hopes of taking over his territory and females. This can result in critical wounds like lost fingers, damaged tails, or even fatalities. Adult females have also been observed chasing off, biting, and injuring unrelated females to force them out of groups, even in documented cases where younger females spent months showcasing submissive behaviors in the hopes of being granted access to the group.
A study from 2021 found that, although primarily diurnal creatures, Guianan red howler monkeys can be quite vocal throughout the night, especially males. The peak hours for this communicative behavior are between 3 AM and 6 AM when the howler monkeys — you guessed it — howl from their home site before beginning their daily activities. This is most likely done for defense purposes, alerting nearby animals of their location so as to avoid confrontation. These calls are very loud and resounding, but their howling calls are longer, with lower frequencies during the daytime. If another group of Guianan red howler monkeys hear this call, they will respond to help ensure that a proper distance is maintained between the two groups. If two groups’ sleeping zones are within a close enough proximity that they can see each other through the canopy, members of each side will face each other and howl, agitate nearby branches, and lunge at the other group.
Another amusing fact: when it rains, it is not uncommon for these monkeys to sit in a crouched position and howl until the rain stops — what crybabies!
Aside from vocal communication, Guianan red howler monkeys also employ olfactory (scent-related) communication, marking their territory in a very…bold way. A group will join up and start defecating together around 30 to 50 feet (10-15m) in the air so that their excretions fall in a massive pile on the forest floor below their sleeping sites. They will also rub their anuses on the tree branches, to really finish the job. Another form of olfactory communication and territory-marking behaviors that males within this species perform is rubbing their mouths on and licking specific tree branches to leave salivary scents.
Though there isn’t enough available research on this specific species to know their exact gestational period, it is safe to assume that, like other Red howler monkeys, Guianan red howler females are pregnant for around 6 months before giving birth to one offspring. Once born, mothers carry their babies around their belly for one month, before allowing the infant to hold onto their back for transportation. This continues for around a year, with the young using their limbs and tails to stay attached to their mother, who doesn’t assist in these efforts. Sometimes these infants will climb onto the backs of other females within the group, or their father, both of which are generally kind and soft in their interactions with the offspring.
In related howler species, females reach sexual maturity around 5 years old, while males take a bit longer at 7 years. Red howler monkeys are polygynous, with the dominant male (and sometimes one of the sub-adult males) mating with numerous females within the group. Mating behaviors are rather saucy, with females using rhythmic tonguing motions to try and seduce the males.
Unfortunately, infanticide is very common during invasions, with adult males killing any of the young that aren’t related to them. Though the females always try to defend their infant by chasing the invading male with loud screams, they are usually unsuccessful. After the loss of an offspring, females become sexually receptive within the next week, usually trying to mate with several males including the one who committed the infanticide. This is to help prevent further losses of their young, as dominant male monkeys within this species won’t threaten their own offspring.
Due to their diverse, folivorous diet that includes fruits and flowers, Guianan red howler monkeys play a huge role in dispersing seeds to help with tree generation. One study, about a different species of howler monkey, found that there was an average of 2.3 species of plants per stool sample within the group they observed. Another study established that seeds have a higher chance of germinating after passing through a howler’s digestive system and that the nutrients in their stool contribute positively to the growth of the sprouting plant.
Plants aren’t the only ones benefiting from the red howler monkey! White-tailed deer, and presumably some other species, are able to eat normally unattainable plant matter by standing underneath the monkeys while they feed and munch the food remnants that drop to the forest floor.
Certain predators of the red howler monkey, including raptors, harpy eagles, jaguars, and caimans, also benefit from their presence in the ecosystem, though unfortunate for the monkeys themselves. To protect themselves from these threats, Guianan red howler monkeys often change up their daily feeding habits (when possible), rest in branches that are at least 40 feet (12 m) high and sleep in tight-knit groups in trees with lots of leaves for camouflage.
The Guianan red howler monkey is listed as Least Concern by the International Union for Conservation of Nature (IUCN, 2021), appearing on the IUCN Red List of Threatened Species. Their population status is trending as stable.
Some threats include human interference in their natural habitats, like livestock farming and ranching, logging and wood harvesting, and other forms of deforestation. This has a serious and adverse effect on these monkeys because they rely heavily on natural landscapes to conceal them from predators. Also, though not a major threat, Guianan red howler monkeys are sometimes affected by hunting and trapping.
Guianan red howler monkeys are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
On top of international legislation and international management and trade controls that protect this species, there are also conservation sites spread throughout their entire range. There are almost 40 National and State Parks and Reserves that protect the Guianan red howler monkey.
We can never be too safe though, and must continue to advocate for the protection of these magnificent creatures!
- https://www.bioexplorer.net/animals/mammals/monkeys/guyanan-red-howler-monkey/
- https://primate.wisc.edu/primate-info-net/pin-factsheets/pin-factsheet-red-howler-monkey/#:~:text=They%20live%20in%20a%20number,river%20Amazon%20in%20eastern%20Brazil.
- https://www.departments.bucknell.edu/biology/resources/msw3/browse.asp?id=12100383
- https://www.iucnredlist.org/species/198622924/198669499
- https://sta.uwi.edu/fst/lifesciences/sites/default/files/lifesciences/images/Alouatta%20macconnellii%20-%20Red%20Howler%20Monkey.pdf
- https://www.researchgate.net/figure/Diel-vocal-behavior-of-the-Guianan-red-howler-monkey-in-Virua-National-Park-Roraima_fig1_355940638
- https://www.mdpi.com/1424-2818/13/11/566
- https://neprimateconservancy.org/colombian-red-howler/
Written by Hannah Broadland, July 2024