Geographic Distribution and Habitat
The mona monkey (Cercopithecus mona) is also known as the mona guenon. It is found in the tropical rainforests of West Africa, spanning a range from Ghana to Cameroon. The mona monkey’s range is focused in the Niger River delta, where they are the most common monkey in the region’s mangrove forests.
This species has adapted to a variety of forest habitats, including secondary and gallery forests. Secondary forests are those that have regrown after deforestation, but have not reached full maturity. Gallery forests, on the other hand, lie alongside rivers and wetlands. They provide a clear view of the water from their trees, hence the name.
Mona monkeys thrive in areas up to 2,000 feet (610 m) in elevation. They do well in the arboreal (tree-dominant) landscapes of the region, as well as the swamp forests in Lagos State, and even the seasonally dry Lama Forest.
Interestingly, mona monkeys have also established themselves on the Caribbean’s Lesser Antilles islands. The largest population here is in Grenada. They were introduced during the 18th century via the slave trade. This scenario is a perfect example of how highly adaptable they are as a species.
The geographic range of the mona monkey is a testament to their adaptability and resilience, thriving in both their native and introduced environments. However, this range is also subject to the pressures of habitat loss and fragmentation, underscoring the need for focused conservation efforts in these regions.
Size, Weight, and Lifespan
Mona monkeys have physical differences between males and females, something known as sexual dimorphism. Males are generally larger and heavier than females. The average head-to-body length of a male mona monkey ranges from 16–25 inches (41–63 cm), and they have a tail length of about 20–29 inches (52–73 cm).
In comparison, females are smaller. Their head-and-body length typically measures between 13 and 18 inches (34 to 46 cm).
In terms of weight, male mona monkeys typically weigh around 11 pounds (5 kg). Females are lighter, averaging around 8.8 pounds (4 kg).
The Mona monkey can live up to 30 years in the wild, as well as in captivity, when cared for under the right conditions.
Monas are striking monkeys. They have large, expressive gold eyes and richly contrasting skin and coat patterns. Their fur is primarily a speckled reddish-brown, providing them with excellent camouflage in the dappled light of their forest habitats.
This coloration is contrasted by white underparts that extend along the arms and up onto the face. Here, you’ll find the biggest mutton chops you’ve ever seen! Underneath the bushy white cheek fur, the monkeys have large cheek pouches that can be filled with food for storage.
Dense white fur also forms the mona’s impressive unibrow. A dark stripe runs along the underside of it, emphasizing the mona’s facial expressions. This is considered an enhancer in their social communications.
The skin around the eyes and on the nose is exposed, showing a soft blue-gray color. This transitions into a pale pink on the nostrils and lips.
A distinctive feature of the mona monkey is the presence of white patches on their hind ends, on each side of their tail. It is a unique characteristic among their species, and is often considered a key identifier for the species in the wild. Just look for the butt patches, and you’ll know you’ve spotted a mona monkey!
The Mona monkey’s diet primarily consists of fruits and seeds. However, they are especially dependent on velvet tamarind and jackalberry trees. During periods of scarcity, such as the dry season, their preferred fruits aren’t as easy to find. They adapt by consuming nectar, flower parts, and particularly the fleshy casings (arils) that cover legume seeds.
One study recorded that 76% of the mona’s diet is made up of fruits, flowers, and seeds, while invertebrates account for 10%. Their flexibility in diet plays a key part in how adaptable the mona monkey is. This is a form of ecological versatility. It also means that having diverse food sources in their habitat is crucial for their survival.
Behavior and Lifestyle
Like many primates, mona monkeys are diurnal, meaning they are active during the day and rest at night. Their daily routine is a balance between foraging for food and resting. This pattern aligns with the availability of their food sources, as well as their need to avoid nocturnal predators.
They are known to travel considerable distances in search of food, guided by the seasonal availability of fruits and other food sources in their habitat. Foraging usually occurs in the morning and late afternoon, when temperatures are cooler. They spend about 60% of their time in the lower canopy, and even venture frequently onto the ground.
During rest periods, mona monkeys like to socialize. Grooming is a common behavior, helping the monkeys strengthen their relationships while keeping clean. Juveniles play a lot to aid their social development and learning.
Little research has been done on mona monkeys. However, based on the fact that they are arboreal (tree-dwelling) monkeys, we can assume a few things are likely. At night, mona monkeys would rely on the safety of the trees to sleep. They probably prefer sleeping in the higher levels of the canopy, where they are protected from ground-based predators.
Their choice of sleeping spots may be strategic—it’s common for primates to choose areas that offer a good balance between safety and proximity to food sources. The sleeping sites might change periodically, depending on food availability and perceived threats.
Mona monkeys have complex social structures. They live in mixed-sex and all-male groups. The average group size is 12 individuals, but larger groups have been observed. Monas tend to live at higher densities when they are not being hunted intensely.
Unlike many other primates, mona monkeys typically have peaceful interactions between the various males in their groups. Aggression is rare.
This is quite different from the other tree-dwelling guenons. So far, scientists think that this could be linked to differences in habitat structures, as well as what and how many resources are available to the groups.
When monas encounter other groups, however, the males’ love for peace can end. They will often become aggressive toward outgroup males. Such behavior helps them strengthen the group’s bonds and maintain their territorial boundaries.
Vocalization is a big part of communication for mona monkeys. They frequently make calls that sound like moans, as well as alarm calls that can sound like sneezes. Males will use “boom” and hacking calls to display their rank and guard their territory—sometimes, these can even sound a bit like a quacking duck! Their vocalizations are generally thought to be harsher than those of closely related species.
Facial expressions and body language are also important communication tools among mona monkeys. More research is needed to understand the intricacies here.
Mona monkeys typically have a polygynous mating system, where dominant males mate with multiple females. The reproductive behavior is influenced by the group’s structure and the dominance hierarchy among the group males.
Unlike in some primates, mona monkey females do not swell in their genitals when they are in “heat” (estrus). So how do males tell when the females are ready to mate? Scientists currently think that they may detect this through their sense of smell. The lack of a visual estrus display also suggests that females may engage in behaviors that initiate mating with the males they select.
Pregnancy (the gestation period) lasts between 5 and 6 months. Generally, a single baby is born, although twins have been seen. Females typically breed every other year. They give birth approximately every 2 years, usually at night, far up in the trees. This birthing strategy likely offers protection from predators.
As in many other primate societies, female mona monkeys bear the brunt of child-rearing duties. There have been no records of males engaging in childcare. With no help from these deadbeat dads, the mothers raise the infants until weaning, when the offspring is 1 year old.
It is another 2 to 5 years before the juveniles reach sexual maturity. At this point, males will usually leave to find another group. Females tend to stay with the groups they were born in.
Mona monkeys play a pivotal role in the ecosystems they inhabit, primarily through their diet and interactions with other species. As frugivores (fruit-eaters), they are crucial for seed dispersal. A mona monkey may travel a significant distance before digesting its food. The seeds are then defecated (pooped out) far from the tree where the fruit originally grew.
Their seed-spreading helps to keep forests diverse, sprouting up new food-producing trees all throughout the ecosystem. This role is particularly enhanced by their cheek pouches, which allow mona monkeys to carry and thus disperse seeds over greater distances than many other animals.
Mona monkeys also contribute to maintaining the balance of predator populations. They are preyed upon by a variety of natural predators, including pythons, which are the only confirmed predators. However, it is believed that other predators such as leopards, golden cats, and crested eagles may also hunt mona monkeys.
This predation plays a role in controlling their population, thus preventing the monkeys from eating too much of the food in their habitat, which could disrupt the ecological balance. If mona populations were to grow out of control, there may be less food available for other species to eat.
The International Union for Conservation of Nature lists the mona monkey as Near Threatened (IUCN, 2019), appearing on the IUCN Red List of Threatened Species. The mona monkey is listed under Class B in the African Convention on the Conservation of Nature and Natural Resources.
Despite their population being in decline, mona monkeys are still widespread in their home range. Their adaptability is helping them thrive in areas where other monkey species have disappeared. This resilience will be their best defense in the face of further degradation of their habitat. Human activity is bound to bring more destruction to their ecosystem, through rapid urbanization and deforestation.
Another significant threat to the mona monkey population is hunting for bushmeat. In many parts of West Africa, humans have started to hunt smaller species like monas because larger primates have started to disappear. In some regions, specific subspecies of mona monkeys have already been eliminated due to these pressures.
The mona monkey 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.
Despite legal protections being in place, a lack of enforcement has led to continued threats to their habitats and, consequently, their populations. This has made effective law enforcement a top priority among conservationists. In Lagos State, Nigeria, studies indicate an urgent need for the enforcement of conservation laws to protect this species.
Monas can be found in several protected areas across their range, including national parks and forest reserves in countries such as Cameroon, Nigeria, Benin, Togo, and Ghana. But even with these protections, the hunting of mona monkeys continues. Some groups of mona monkeys benefit from additional protection in community forests, and those considered sacred by locals.
Based on research, conservationists recommend that conducting regular anti-poaching patrols can go a long way toward protecting mona monkeys and other primates. In addition, traditional clear-cut logging practices should be given up in favor of selective logging. With this approach, only certain trees are cut down, minimizing the harm that is done to the monkey’s habitat.
Community education about the ecological role of mona monkeys is another key tool in conservation work. When local people have a better understanding of how mona monkeys keep their forests healthy, there will be more success in protecting this declining species.
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Written by Amanda Riley, November 2023