Geographic Distribution and Habitat
Also known as Wolf’s mona monkey, Wolf’s guenon is a colorful Old World monkey native to Central Africa. The species’ range includes the countries of Uganda and the Democratic Republic of the Congo (DRC) where the primates can be found in primary (mature) and secondary (younger) lowland forests and also residing in swamp forests, along riverbanks.
In the DRC, Wolf’s guenons occupy a variety of habitats south of the Congo River (formerly known as the Zaire River), in an area known as the Congo Basin. Home to 10,000 species of tropical plants—30 percent found nowhere else on earth—and home to endangered wildlife species, the Congo Basin is one of the most important wilderness areas remaining and is the world’s second-largest tropical forest.
The three subspecies of Wolf’s guenon are separated by swamp forest.
- The Congo Basin Wolf’s monkey, C. wolfi wolfi is found between the Congo and Sankuru Rivers.
- The fire-bellied Wolf’s monkey, C. wolfi pyrogaster is found between the Kwango and Kasai-Lulua Rivers.
- The Lomami River Wolf’s monkey, C. wolfi elegans is found between the Lomami and Lualaba Rivers.
Size, Weight, and Lifespan
Head-to-body length in male Wolf’s guenons ranges from 17.5 to 20 in (445 to 511 mm), with an average length of 19 in (485 mm). Their tails add another 27 to 32 in (695 to 822 mm), with an average tail length of 31 in (779 mm). Males weigh between 8.37 and 9.26 lb (3.8 and 4.2 kg).
Head-to-body length and tail measurements for female Wolf’s guenons is not available; however, the “ladies” are considerably smaller than their male counterparts, weighing between 5.29 and 6.8 lb (2.4 and 3.1 kg).
In another indication of their sexual dimorphism; that is, the different physical characteristics between males and females of a species, male Wolf’s guenons are equipped with much larger canine teeth than the females.
The forelimbs and hindlimbs on both male and female Wolf’s guenons are nearly equal in length, giving these monkeys stability as they traverse through the forest quadrupedally, on all fours.
Lifespan in the wild for Wolf’s guenon is 20 to 26 years.
The Wolf’s guenon’s expressive face is characterized by gold-brown eyes; a long, dark flat nose; and a pink mouth and chin. Dark fur covers the cheekbones, and long, yellowish fur covers the lower face. A few of these yellowy strands sprout from the monkey’s chin. A bushy gray brow ridge (like a grandpa’s bushy eyebrows) feathers out to a reddish tuft that sits atop either ear.
The back of this lithesome monkey is cloaked in dark gray fur with a reddish splotch at the center. Forelimbs are dark gray to black fur, hindlimbs are a light reddish-brown color, and underparts are a white to pale yellow. The Wolf’s guenon’s tail is dark gray at the base, turning black as the fur extends to the tip.
Fur color varies with subspecies. Guenons rely on fur coloring to recognize one another and for attracting potential mates.
Guenons have enormous cheek pouches that they stuff with fruit collected while foraging—so they can later enjoy a nice fruit snack from a safe perch in the forest canopy.
Callous-like patches on the monkeys’ buttocks, scientifically known as ischial callosities, provide the monkeys with a measure of comfort while they are sitting in branches or resting.
Males have a blue scrotum (common in Cercopithecus species), which scientists speculate may be important when it comes to attracting females.
Wolf’s guenon monkeys are considered frugivorous, meaning that they eat a lot of fruit! They supplement their diet with young leaves (easier to digest than mature leaves), seeds, flowers, nectar—and the occasional insect.
Habitat determines the types of fruits and dietary supplements that Wolf’s guenons eat.
Behavior and Lifestyle
Wolf’s guenon is a diurnal species, meaning that these monkeys are active during daylight hours. Spending most of their time in trees (making them arboreal), they cavort through the forest at an average height of 49 to 82 ft (15 to 25 m) above the ground.
The name “Wolf” is derived from the name of the scientist, Dr. Ludwig Wolf, who first documented this species. In 1887, Dr. Wolf took one of these primates from the monkey’s home in central west Africa and brought the monkey to the Zoological Garden at Dresden, Germany. This monkey died in 1891.
Group size ranges from 1 to 12 individuals, with a lone male or a single alpha male leading a multi-female troop. Females remain with their birth groups. However, young males, after reaching puberty, leave their birth group and may form bachelor groups; that is, groups of young male monkeys who seek and aspire to establish and lead their own female harem. Occasionally, a brazen bachelor might attempt to oust an alpha male of an already established troop, to gain mating rights to the troop’s females.
Larger groups typically split into smaller groups to forage. Wolf’s guenons primarily forage and feed during the early morning and early afternoon hours, with rest breaks between.
Wolf’s guenons are commonly found in the company of other primate species, most often black crested mangabeys but also with bonobos, colobus monkeys, red-tailed monkeys, and other guenon species. Scientists speculate that these mixed groups most likely form for the purpose of enhanced predator detection: the more monkeys, the more eyes and ears alert to potential danger.
To reduce competition with one another, dietary predilections (food habits) are an important consideration of these interspecies gatherings, with the different primates feeding on different foods, foraging at different heights in the forest, or alternating their eating and nap times.
Although Wolf’s guenons most often initiate gatherings with other primates, they show less consideration and grace toward other Wolf’s guenons. Highly territorial, both males and females behave aggressively when Wolf’s guenons from another troop encroach into their home range. Females often sound the alarm, bringing the alpha male to defend his group’s territory.
In addition to alarm calls, vocalizations of Wolf’s guenons include travel calls and contact calls. Of note: many guenons have learned to recognize the alarm calls of other monkeys, sounded during interspecies gatherings, enabling them to appropriately react to a potential threat—should another primate spot a leopard or an eagle, for example.
A common Wolf’s guenon alarm call is the sneeze call, a short call that sounds… like a sneeze.
To maintain contact with each another while foraging, Wolf’s guenons occasionally grunt to announce their position in the forest canopy. These monkeys are more vocal when hunting for insects than they are when foraging for fruits or leaves.
To communicate territoriality, males let out a boom call, which is a low, short tone that can be carried long distances thanks to resonating air sacs inside the monkey’s vocal chamber.
Posturing adds drama to alarm calls and is another aspect of this species’ communication repertoire.
A yawning male Wolf’s guenon is not sleepy. Rather, by opening his mouth and revealing his canine teeth, he is sending a message of tension and aggression to an intruder.
Wolf’s guenon males will also stare-down an intruder while flattening their ears, stretching their facial muscles, and retracting their scalp. If this scary-face display proves inadequate in intimidating the intruder, they will hang open their mouth, while keeping their teeth hidden, and begin bobbing their head. A successful intimidation will elicit a fear grimace from the intruder primate. In what looks, to us, like a smile—but is not—the threatened intruder monkey retracts his lips and bares his clenched teeth in a show of deference to his aggressor—thereby diffusing the potential for being attacked by the annoyed alpha male.
Grooming, an activity that Wolf’s guenons perform extensively, is an important tactile communication that strengthens their social bonds with one another.
Scientists speculate that the species may use certain chemical clues; pheromones, for example, might be used to attract a sexual partner.
Wolf’s guenons are polygynous; that is, the alpha male gets to mate with all the females in his group. Copulation, however, is usually initiated by females. To entice the alpha male, a female will flash him with her genitals. Maintaining her coquettishness, a female will look over her shoulder and pout—extending her lower lip—as she looks up at the male while the two engage in copulation. Scientists have said that this feminine nuance serves no reproductive function.
Both males and females reach sexual maturity at 4-1/2 years old, and females are between 4 and 5 years old when they produce their first young. They give birth to a single offspring (twins are rare) after a gestation period of about 5-1/2 months. Most births occur between June and December when the greatest abundance of food is available. Birth intervals (how often the females give birth) is not documented for this species.
Scientists have observed Wolf’s guenon mothers carrying their babies upon their backs for the first few months of their infants’ lives. Other females in a group might help with parental care.
Infants are considered weaned at six months of age, at which time they become independent.
Wolf’s guenons help the regeneration of healthy forests by dispersing seeds through the foods that they eat. They may also contribute to pollination when they drink nectar.
The Wolf’s guenon is listed as Near Threatened by the International Union for Conservation of Nature (IUCN, 2016), appearing on the IUCN Red List of Threatened Species. The main threat to Wolf’s guenons is hunting for the commercial bushmeat trade across its geographic range and habitat loss. It is suspected that the species has undergone a population decline in the order of 20–25% over the past 30 years, so is listed as Near Threatened. These declines are expected to continue.
Although their small size and their arboreal nature makes them vulnerable to predators, including crowned hawk eagles and, sometimes, leopards—humans have most recently become the major predator of Wolf’s guenons, hunting and killing these colorful monkeys to supply the bushmeat market. Humans are also responsible for continuing to destroy the Wolf’s guenon habitat, at an alarming rate, for agricultural use and to supply the lumber industry.
The occasional raid carried out by Wolf’s guenons on local agricultural crops (in habitat that once belonged to these primates) and their potential for carrying diseases that can be contagious to humans has not helped endear the species to locals.
The Wolf’s guenon is 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.
Research revealed no local or national conservation efforts on behalf of Wolf’s guenon. However, several zoos are engaged in captive breeding and educational awareness programs: the Sacramento Zoo and San Diego Zoo, both in California; Zoo Atlanta in Georgia; and the San Antonio Zoo in the state of Texas. In 2006, the San Antonio Zoo took in two baby Wolf’s guenons after hunters killed the infants’ mothers, leaving the babies bushmeat orphans.
Written by Kathleen Downey, July 2017