CAMPBELL'S MONA MONKEY
Geographic Distribution and Habitat
Native to numerous countries along the western coast of Africa, Campbell’s mona monkeys (Cercopithecus campbelli), also called Campbell’s monkeys and Campbell’s guenons, are right at home in a wide variety of habitats, including primary and secondary lowland forest, gallery forest, mangroves, woody savannas, and even areas used for agriculture. They live up to an elevation of 2,000 feet (610 m).
Campbell’s mona monkeys were formerly considered to be a subspecies by the scientific name Cercopithecus campbelli campbelli. In 2005, another subspecies, C. campbelli lowei, was raised up as a distinct species, and Campbell’s mona monkeys followed suit. However, in recent years, studies in the two species’ anatomy, ecological roles, and vocalizations show very little difference between them, and populations have even been found with features of both species. Further study is needed to find out whether these two species are truly distinct.
Size, Weight, and Lifespan
Unfortunately, specific body size measurements for Campbell’s mona monkeys are lacking in the scientific literature. Based on other related species, they likely have a body size between 16 and 21 inches (32–53 cm) and a tail length of 26–35 inches (67–90 cm). Females weigh about 9 lbs (4 kg) and males are slightly larger at about 11 lbs (5 kg). They likely live to an age of about 30 years.
When a species ceases to exist in a geographic area they once occupied.
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Campbell’s mona monkeys have an interesting coloration, with black or gray arms, legs, and lower back, a brownish-yellow upper back, and a large puffy white chest ruff. The upper half of their face is yellow and the sides are gray. The middle of their face is bare and mostly gray, with pink below the nose. Their amber eyes are large and expressive. They have a long, skinny black tail that helps them move about through the forest. There is no sexual dimorphism other than the males’ larger size.
Campbell’s mona monkeys mainly consume fruit and insects. One study found that their diet breakdown is 46% fruits, 33% animal matter (mostly insects), and 8% leaves. A main way they forage for insects is to unroll curled-up leaves.
Behavior and Lifestyle
Campbell’s mona monkeys are diurnal (active during daylight hours) and arboreal (tree-dwelling), spending nearly their whole lives in the trees. There is little information available about their behavior beyond that; however, details can be inferred from related species. They are likely very active, moving swiftly and agilely throughout the trees. They leap between trees by running down the length of a branch and jumping onto another, landing on all fours.
Campbell’s mona monkeys have a vocalization that means the equivalent of a human’s “Timber!” when a tree falls. It’s been described as sounding like “boom boom krak-oo krak-oo.”
Campbell’s mona monkey groups are typically composed of one male and multiple females, although all-male bachelor groups and multi-male and multi-female groups have also been observed. An average group has about 10 individuals. Their home range size was estimated for two groups at 128 and 166 acres (52 and 67 ha). The females within the group tend to be very socially close, with the male interacting less often with other members of the group. Instead, his role tends to center on defense of the group and leading travel.
Campbell’s mona monkeys, while relying on a wide variety of communication types, are well known for their highly developed vocalization skills. Females, which make up the majority of adults in a group, communicate with each other extensively, both physically and vocally. They have a much wider array of vocalizations than males, including call types to indicate distress, threats, and contact with another group. Males vocalize much less often, and usually only to maintain spacing within the group and to warn of predators.
Studies show that Campbell’s mona monkeys may even use a rudimentary form of syntax, with different vocalizations having very specific meanings. For example, one study found that the call described as “krak” was only ever made after contact with a leopard and “hok” after contact with a crowned eagle (or, occasionally, a flying squirrel, whose silhouette resembles that of a crowned eagle). Meanwhile, “krak-oo” and “hok-oo” were used as general alarm types, usually associated with a predator. “Boom” calls were only given in non-predatory contexts, such as a falling tree or during fights with neighboring groups. This type of vocalization is significant, because it may indicate that Campbell’s mona monkeys add a suffix (“-oo”) to the end of a “word” to change its meaning, something that has not been shown in any species besides humans.
More research adds another level of complexity to the monkey’s vocalizations. For example, two consecutive “boom” calls are used to gather other monkeys nearby, while “boom boom krak-oo krak-oo” is used when a branch is about to fall—like “Timber!” for a human. When a “krak” is followed by multiple “krak-oo”s, it means that not only is there a leopard in the vicinity, but that it poses an immediate threat.
There is an ongoing debate as to whether a vocalizing Campbell’s mona monkey intends to inform its groupmates about a predator or event or whether the vocal response is purely instinctive. Evidence for the latter is the fact that males vocalize in response to falling trees even when all groupmates are close enough to witness it. This may suggest that the vocalization is not intended to inform, but is an instinctive response. However, the vocalization may also serve to let groupmates know that the vocalizer is safe, and to gather the group to a central area after they may have scattered in response to the falling tree. What everyone can agree on, however, is that Campbell’s mona monkeys present an exciting and novel opportunity for researchers to learn more about complex vocalization in non-human species.
Very little is known about Campbell’s mona monkeys’ reproduction. However, because most groups have a single male and multiple females, they likely have a polygynous mating system in which one male mates with multiple females. Based on related species, their gestation period is likely between 5 and 6 months. A female’s baby is weaned at about a year of age, and she can give birth again when her older child is about 2 years old. Sexual maturity occurs anywhere between 2 and 5 years of age, and the generation length is about 12 years. It is unknown what role the male plays in child rearing, but because of the group structure, he likely does not play a significant role in parenting.
Campbell’s mona monkeys are preyed upon by leopards (Panthera pardus), Western chimpanzees (Pan troglodytes verus), and crowned hawk-eagles (Stephanoaetus coronatus). As fruit eaters, they likely serve a role as seed dispersers.
Campbell’s mona monkeys are listed as Near Threatened by the International Union for Conservation of Nature (IUCN, 2019), up from a Least Concern assessment in 2016. This assessment is due to their declining population, habitat loss of over 30%, and human population growth in their native countries over the last 36 years, or three generation lengths. Luckily, Campbell’s mona monkeys still have a wide distribution and are adaptable to change and able to survive in degraded habitats in certain circumstances.
Unlike most primate species, the most significant threat against Campbell’s mona monkeys isn’t habitat loss, but hunting (although habitat loss is a close second!). Campbell’s mona monkeys haven’t historically been a prime hunting target because of their small size, but because larger primates such as the Upper Guinea red colobus (Piliocolobus badius) and the king colobus (Colobus polykomos) have been largely extirpated from the Campbell’s mona monkey’s range, even small primates are becoming hunting targets. Researchers have found that an adult male carcass can be sold for about $8.80 (USD) in markets in southwestern Côte d’Ivoire, a significant source of income in a country in which just under half of all residents live in poverty.
While not the prime threat, habitat loss is still a significant source of population decline for Campbell’s mona monkeys. This loss is mainly due to deforestation, forest fragmentation, and forest conversion for the agriculture, mining, and creation of roads. Even the disturbed habitats that Campbell’s mona monkeys once thrived in are increasingly being converted into plantations of non-native species.
Campbell’s mona monkeys are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES) and Class B of the African Convention on the Conservation of Nature and Natural Resources. Campbell’s mona monkeys are protected by a number of protected habitats throughout their range, such as Taï National Park in Côte d’Ivoire, North Lorma National Park in Liberia, and Gola Forest National Park in Sierra Leone.
- Lemasson, A., Gautier, J., Hausberger, M. 2003. Vocal similarities and social bonds in Campbell’s monkey. C. R. Biologies, 326, 1185-1193.
- Ouattara, K., Lemasson, A., Zuberbuhler, K. 2009a. Campbell’s Monkeys Use Affixation to Alter Call Meaning. PLoS One, 4(11).
- Ouattara, K., Lemasson, A., Zuberbuhler, K. 2009b. Campbell’s monkeys concatenate vocalizations into context-specific call sequences. PNAS, 106(51).
Written by K. Clare Quinlan, April 2021