Pan troglodytes ellioti
Geographic Distribution and Habitat
The Nigeria-Cameroon chimpanzee (Pan troglodytes ellioti), sometimes called Elliot’s chimpanzee, is native to the two African countries that give it its namesake. Geographic distribution is restricted to isolated patches of forest within southwestern Nigeria, the Nigeria Delta and floodplain, and to Nigeria’s eastern border north of the Sanaga River, before stretching southwesterly into the forests of Cameroon.
Habitat for this once widespread, and now Endangered, primate includes primary and secondary moist lowland forest, montane and submontane forest. In Cameroon, the subspecies is composed of two genetically distinct populations. Each occupies a different ecological niche: one group resides in the country’s western rainforests, while the other resides in central Cameroon’s forest-woodland-savanna mosaic ecotone, which includes include gallery forest, dry forest, semi-deciduous forest, and open grasslands. An ecotone is a region of transition between biological communities.
Farmland provides Nigeria-Cameroon chimpanzees with an unnatural, inapposite habitat.
The discipline of taxonomy is fluid, often yielding new discoveries. Currently, the International Union for the Conservation of Nature (IUCN) recognizes four subspecies of the common chimpanzee (Pan troglodytes), assigning each a conservation status. Subspecies classification is based, in part, on differences in appearance and distribution.
- Nigeria-Cameroon chimpanzee (P. t. ellioti), Endangered
- Western chimpanzee (P. t. verus), Critically Endangered
- Central chimpanzee (P. t. troglodytes), Endangered
- Eastern chimpanzee (P. t. schweinfurthii), Endangered
Genetic data shows a close evolutionary relationship between Nigeria-Cameroon and western chimpanzees. In fact, prior to receiving its own subspecies classification in 1997, the little-studied Nigeria-Cameroon chimpanzee had been recognized as a western chimpanzee (the two share a common ancestor from 0.4 to 0.6 million years ago!). The central and eastern chimpanzees share their own evolutionary relationship.
Further genetic and ecological research may lead to the recognition of more or fewer subspecies classifications, within the common chimpanzee’s descending taxonomic hierarchal order. More importantly, additional studies could help researchers better understand and, hopefully, preserve all four common chimpanzee subspecies—including the enigmatic and rare Nigeria-Cameroon chimpanzee.
Size, Weight, and Lifespan
Sexual dimorphism—differences in size or appearances between the sexes—is pronounced in this subspecies. Adult male Nigeria-Cameroon chimpanzees can weigh up to 154 lb (70 kg) and stand up to 5.6 ft (1.7 m) tall. Females are significantly smaller in size and stature, weighing between 57 and 110 lb (26 to 50 kg).
Lifespan for chimpanzees in the wild is about 38 years of age—relatively the same maximum lifespan as early human hunter-gatherers. Given that we humans share nearly 99 percent of our DNA with chimpanzees (and like chimpanzees, we are great apes), our own ancestors’ similar lifespan is not surprising.
Captive chimpanzees have slightly shorter lifespans than that of their free and wild brethren. An exception is a captive female, known as “Little Mama” who was believed to be in her early 80s when she died in 2017 at a Florida safari park.
Nigeria-Cameroon chimpanzees may not be camera-shy, but these barrel-chested primates are elusive. Photographs of this Endangered subspecies in their wild habitat are scarce. Furthermore, a lack of DNA testing of captive individuals makes distinctions between the four subspecies difficult. That said, based on the slim information they have gleaned, researchers have conjectured that Nigeria-Cameroon chimpanzees have a darker face, longer hair on the sides of their head and cheeks, and slightly smaller ears than the other chimpanzee subspecies.
Apart from any nominal characteristics that may distinguish this subspecies, the Nigeria-Cameroon shares physical traits typical of all chimpanzees.
A sturdy body is covered with dark brown or black hair. The face, ears, palms, and soles of feet are bare. Rumps of infant chimpanzees are adorned with a white tuft of hair that disappears as an individual ages. Being great apes, chimpanzees lack a tail. Long arms dangle below the knees, and their hands are fitted with long, slender fingers and short, opposable thumbs. They have an opposable big toe on each foot that can pluck fruits from trees.
Chimpanzee faces are full of character. A dramatic, bony brow ridge (known as a sagittal crest) defines the forehead, beneath which Mother Nature has set brown, animistic eyes that assess the world. A flattened muzzle gives way to a wide mouth with slightly protruding lips. Inside that mouth is a set of 32 teeth, same as adult human primates. Like humans, chimpanzees have two sets of teeth in their lifetime: a set of “baby teeth” that fall out as the chimpanzee grows older, and a second set of permanent teeth, usually by the time an individual is 11years old. Unlike humans, the canine teeth—or fangs—of chimpanzees are gigantic and razor-sharp (used primarily for intimidation). Their incisor teeth allow them to snip fruits and nuts from trees, while their molar and premolar teeth grind and crush their plant-based meals.
Faces of adults are dark brown or black and might sport a few white whiskers on the chin. Younger chimpanzees have pinkish-white faces and no “beard.” Outlandishly large ears grace either side of the chimpanzee’s head.
As chimpanzees grow older, both males and females may begin to lose the hair on their head, leaving a bald patch above the sagittal crest. And those once-lustrous black back hairs begin to gray.
Images captured from a 2018 camera trap survey in Cameroon are believed to be Nigerian-Cameroon chimpanzees. A family group is going about its day, unaware of being surveilled, giving researchers a glimpse at the stocky, hirsute individuals.
Like all chimpanzees, Nigeria-Cameroon chimpanzees are omnivores: they eat foods that are of both plant and animal origin. Their diet fluctuates with the seasons and varies with their geographic location. That said, about half their diet is comprised of fruits; they prefer ripe fruits and have a special proclivity for figs, which are high in nutrition and provide a superior energy source. Young leaves along with stems, buds, pith, resins, bark, and seeds supplement the plant-based portion of their diet. Insects, small vertebrates, and eggs provide the chimpanzees with animal-based protein.
Unlike western and eastern chimpanzees who are known to kill and eat small monkeys, including the western red colobus (Procolobus badius), and then share their meal with other troop members (even when an individual did not partake in the hunt) researchers have not definitively concluded that Nigeria-Cameroon chimpanzees routinely kill and eat the flesh of other mammals. But at Cameroon’s Tofala Hill Wildlife Sanctuary, a lone adult Nigeria-Cameroon chimpanzee was caught on a camera trap video feeding on the body of a mongoose. (He did not share his meal with other group members involved in the hunt.) In another instance, wildlife biologists observed a Nigeria-Cameroon chimpanzee predation attempt on a Preuss’s red colobus (Procolobus preussi) within Cameroon’s Ebo Forest. These isolated observations suggest that these great apes might be at least partially carnivorous.
Chimpanzees are known to eat dirt, a practice known as geophagy. Mineral-rich soil surrounding termite mounds is especially desirable. Eating dirt is thought to release anti-malarial properties in the plants that chimpanzees consume. Regular consumption of soil might also strengthen a nursing mother’s immune system. And dirt-eating chimpanzees are, apparently, less desirable hosts to parasites.
Behavior and Lifestyle
Chimpanzees are both arboreal and terrestrial, meaning they spend time in the trees as well as on the ground. They are active during daylight hours, making them diurnal. Most of their day is spent in the treetops, foraging, and eating. Peak feeding periods occur early morning and mid-to-late afternoon, with rest periods and mutual grooming sessions happening in between.
The structure of chimpanzees’ hands has evolved so they can use their palms as “hooks” to climb trees and grasp fruits. Although their short, opposable thumbs offer a bit of assistance in these activities, it’s the middle finger, in consort with the thumb (rather than index finger to thumb) that assists with manipulations requiring greater dexterity. (Contrast this middle-finger usage with human primates who are known to use this digit for “communication purposes.”) To advance through the forest, chimpanzees swing by their long arms from tree limb to tree limb, an arboreal form of locomotion known as “brachiation.”
While on the ground, chimpanzees either walk on all four limbs (quadrupedally) or upright (bipedally). When walking quadrupedally, chimpanzees appear to be strolling. With legs much shorter than their arms, they lean forward and extend their hands to the ground, curling their fingers upward into their palms so that their knuckles bear the weight of their body as they walk. There is a name for this type of quadrupedal locomotion: knuckle walking. Gorillas also engage in this type of walking, as do anteaters and platypuses! Although chimpanzees are able to walk bipedally for up to a mile, they tend to walk in an upright position for short intervals. Their stride looks a bit different than that of their human cousins when walking upright. Whereas the thighs of humans tend to slope inward, the thighs of chimpanzees slope outward, giving them a bow-legged gait.
After a day of foraging, eating, socializing, and grooming one another, it’s time for bed. Each evening, chimpanzees create a new sleeping nest using twigs and other plant matter. Nests include a “mattress” and a cover that provides a measure of concealment. Mothers share their nests with their unweaned infants, but juveniles and adults sleep alone.
Like all chimpanzees, Nigeria-Cameroon chimpanzees demonstrate intelligence, innovation, and skill with their prowess for refashioning forest flora and minerals into tools for use in their daily lives. Modified twigs, sticks, and stems become instruments to extract ants, bees, termites, and other bugs from their hiding places. Rocks become sledgehammers to crack open hard-shelled nuts. Leaves are used to collect water or used as napkins to catch juicy fruit residue from a chin, following a meal.
Chimpanzee aptitude extends beyond tool usage; these great apes routinely use local flora for medicinal purposes. As example, an individual suffering from an upset tummy might suck on the bitter pith (stem) of a plant, thereby releasing healing compounds that provide relief. Nigeria-Cameroon chimpanzees have been observed using 13 plant species to treat various illnesses, including abdominal upsets and parasitic infections.
Leopards and large snakes—and in some cases, baboons—are natural predators of chimpanzees. Infant chimpanzees are at greatest risk of such predation. But a study reported in the July 2021 American Journal of Primatology (“Environmental and anthropogenic effects on the nesting patterns of Nigeria–Cameroon chimpanzees in North‐West Cameroon”) found humans to be the sole predators of Nigeria-Cameroon chimpanzees.
Chimpanzees may be our closest genetic relative, but we humans are not directly descended from them. Rather, humans and chimpanzees share a common ancestor from whom we each evolved—4 to 8 million years ago!
A female chimpanzee is known as an “empress.”
A male chimpanzee is known as a “blackback.”
Nigeria-Cameroon chimpanzees live in social family groups, typically comprised of 4 to 12 individuals. Contrast this group size to other chimpanzee subspecies from other parts of the African continent, where group size can range from 2 to 150 individuals! Family groups are smaller for Nigeria-Cameroon chimpanzees due to fragmented habitat and competition for food and breeding partners.
An alpha male is entrusted with protecting his family group and their territory; he rules more through power of persuasion, rather than might. Otherwise, a chimpanzee community is rather loosely structured, with a linear hierarchy. A female’s dominance is even less pronounced, though her offspring inherits her status within a family group. Upon reaching sexual maturity, females migrate to neighboring communities to mate. A group’s males, however, remain with their natal (birth) group. These “momma’s boys” are known to share lifelong bonds with their mothers.
When headed out for a day of foraging, chimpanzees travel in smaller subgroups, or alone, with everyone reconvening as a complete group later in the day (a practice described as “fission-fusion”). Males tend to travel in larger subgroups, while females more often travel alone or with their dependent offspring. Occasionally, two mothers travel together with their children in tow—allowing for impromptu playtime between the little ones!
Chimpanzees are able to discern and recognize individuals not only in their own family group but also those whom they may have met in previous encounters, indicative of a robust memory. (Indeed, studies of captive chimpanzees who’ve been taught sign language not only recall how to sign, but they also recall their human primate teachers, even after lengthy separations.)
Home ranges for chimpanzees are strongly influenced by habitat. Within forested habitats, home ranges are between 1.9 and 19 sq mi (5 to 50 sq km), with an average of 4.6 sq mi (12 sq km). Within savanna habitats where food sources are widely dispersed, chimpanzees must travel farther, between 46 and 216 sq mi (120 to 560 sq km). Lucky for them, they can travel at speeds up to 25 mi (40 km) per hour!
The number of individuals in a family group and the proximity of hostile neighboring groups are additional factors affecting home range.
Generally, males travel more broadly than females who tend to keep within a core area of their home range—unless a female is in estrus. Then she may range as far as males, alongside them, for mating opportunities.
Chimpanzees are not known to be welcoming hosts to outsider chimpanzees. Always on alert to interlopers, they patrol their territory by walking in a single line formation along its borders. Should they encounter trespassers, they will vigorously defend their turf—sometimes to the death.
Other species who make their home in Cameroon include Cross River gorillas, western lowland gorillas, central chimpanzees, and Pruess’s monkey (Allochrocebus preussi). Nonprimate species include forest and savanna elephants and the African golden cat.
Nigeria hosts western lowland gorillas, chimpanzees, lions, leopards, mongooses, hyenas, side-striped jackals, African buffaloes, African elephants, pangolins, and a bevy of other magnificent and diverse animals.
Nature has given chimpanzees the ability to express themselves and communicate with one another through a variety of means, including 30 recorded vocalizations. A wide range of emotions are expressed through these calls. Notably, chimpanzees elicit different warning calls in association with specific predators.
Out of all their vocalizations, the “pant-hoot” is perhaps the one that most of us human primates associate with chimpanzees. This structurally complex, long-distance call is a sequence of shrieks and roars. It begins softly, almost tentatively, gradually building in intensity with in-and-out pants, culminating in a series of frenetic, high-pitched screams, before gradually quieting. Pant-hoot calls carry a distance up to 1.2 mi (2 km). Both males and females engage in the pant hoot, though it is more commonly heard from a group of adult males, collectively pant-hooting in chorus.
The pant hoot call serves multiple purposes. Chorusing among males is thought to cultivate “brotherly” friendships. High-ranking males emit pant-hoots to proclaim their dominance or strength over other group members. An individual who comes upon a tree laden with fruit announces his find to fellow members with a pant-hoot call. Pant hoot calls are also used by individuals to communicate their location to one another while foraging.
While the pant-hoot is certainly impressive, it’s their facial expressions, hand gestures, and postures that most often indicate what’s on their mind. In fact, an international team of researchers found that wild chimpanzees communicate through hand gestures in a manner that follows human linguistic rules. They posit that despite chimpanzees’ inability to speak human language, the foundations of the two species’ respective communications systems follow the same basic mathematical principles. Human speech may have evolved from gesturing! Researchers have stated that the communication systems of human toddlers and chimpanzees are remarkably similar.
Chimpanzees do not have a poker face. Stink eye, maybe. This penetrating stare is meant as a threat. When angry or threatened, they curl their wide lips apart into what appears to be a smile. But this “fear smile” (as it is colloquially referred to by wildlife biologists) is not indicative of happiness or contentment. When they wish to intimidate a potential predator, chimpanzees flash their giant, fearsome fangs. This toothy threat might be accompanied by slapping the ground or raising the arms overhead while standing fully upright. In a phenomenon described as “piloerection,” the hairs on an individual’s body bristle to stand on end, making the chimpanzee appear larger than his actual size and, hence, a greater threat. (We may have witnessed this occurrence in dogs. When fearful or angry, the hairs around a dog’s neck bristle and stand up. We call these hairs “hackles.” In human vernacular, we might warn someone against “raising our hackles,” which means “you better not anger me, or else. . .”).
In chimpanzee culture, foot stomping is an overture of randy males directed at a particular female with whom they wish to mate. Or a male might engage in more subtle flirtation by tearing strips of leaves with his teeth to get a female’s attention. Chimpanzees are known to greet and comfort one another with an embrace. They kiss, hold hands, and even tickle one another.
Lip smacking or teeth clacking can be heard by an individual who is lost in the Zen of grooming another. Like other nonhuman primates, mutual grooming is an important daily activity for Nigeria-Cameroon chimpanzees. This activity serves a greater purpose than just picking parasites off of one another; “allogrooming” helps to instill and strengthen social bonds and establish trust among group members. Scratching one’s own body part in the presence of another is an invitation to be groomed. A mother who wishes to invite her little one to hop onto her back will present her rear end and extend her foot, exposing the sole.
Communication studies of captive chimpanzees leave no doubt as to their exceptional intelligence. Researchers have taught these chimpanzees to communicate through American Sign Language. Other captive chimpanzees have been taught to remember and apply abstract mathematical principles (symbols, shapes, sizes). An indication of self-awareness, chimpanzees recognize their reflection in a mirror.
Because Nigeria-Cameroon chimpanzees have been so little studied, we must look to the parent species, the common chimpanzee for clues to reproductive behavior. Like their human primate cousins, chimpanzees reach sexual maturity in their early teens. At age 13, females are able to conceive and bare young. Males develop sexually a bit later, able to sire young by the time they are 16 years of age.
Chimpanzees are polygynandrous; that is, both males and females mate with multiple partners. The species has no defined breeding season and births occur year-round. When she is in estrus, a female’s bright pink anogenital skin swells, eliciting maximum male attention.
After a gestation period of about 8 months, a female gives birth to a single infant (rarely, twins). She will not give birth again for another five years (for captive chimpanzees, living under artificial conditions and who are controlled by their human captors, birth intervals are shorter). Typically, a mother in the wild gives birth to three children in her lifetime.
Newborns instinctively cling to their mothers. They will nurse for the first five years of their lives, before they are finally considered weaned. Youngsters begin exploring their surroundings but remain in their mothers’ “orbit” for their first decade of life. They learn survival skills—including what foods to eat, how to construct a sleeping nest, how to refashion sticks into tools— by watching their mothers. As primary caregivers to their children, mothers have a lot of responsibility. Fortunately, older siblings and related females lend a hand. Youngsters learn to develop social skills by playing with others their age and by grooming each other.
Although fathers and mothers do not form long-term bonds with one another, a group’s males (whether or not they are biological fathers) protect and play with the children.
Nigeria-Cameroon chimpanzees are ambassadors of their forest ecosystem. Thanks to the many fruits they consume, they help replenish their forest habitat by dispersing seeds—via their feces—along all that ground they cover through their long-distance foraging expeditions. They also act as nature’s gardeners by pruning overgrowth from trees as they pluck fruits. The loss of these essential ambassadors, therefore, would threaten the forest ecosystem in which they live, and another piece of our world (along with one of her most vital citizens) would disappear.
The Nigeria-Cameroon chimpanzee is classified as Endangered by the International Union for Conservation of Nature (IUCN, November 2015), appearing on the IUCN Red List of Threatened Species. Its limited geographic range is the smallest of the four subspecies, and it has the smallest population with less than 6,000 individuals, total.
Where it is most threatened, within southwestern Nigeria and northwestern Cameroon, less than 250 individuals are thought to reside in each area. Researchers fear a further population decline of 80 percent by 2060 and, thus, call for the species to be classified as Critically Endangered for these subregions.
These chimpanzees are under siege from anthropogenic activities. Pristine tracts of forest are being chopped down to supply the logging industry or burned to the ground and transformed into farmland and oil-palm and rubber plantations. Human settlements are increasingly taking over Nigeria-Cameroon chimpanzee habitat, forcing the primates into isolated and unsustainable forest fragments. A growing human populace puts the chimpanzees at risk of emerging diseases. Nigeria-Cameroon chimpanzees are also illegally hunted (poached) and killed for their flesh, known as “bushmeat.” For years, chimpanzees were treated as biomedical research subjects (whether kidnapped from the wild or born in captivity) and endured invasive and painful experiments, purportedly in the name of science. Ethical concerns and outcry from animal rights groups prompted humane legislation that forced the U.S. National Institutes of Health (NIH), in 2013, to end its support for invasive research on chimpanzees and to retire most of its captive research chimpanzees to sanctuaries. Other countries had already banned this invasive research on chimpanzees.
Bad actors in the illegal wildlife trade are culpable for kidnapping and selling chimpanzees as pets. But chimpanzees do not make good pets. They are wild animals who grow from helpless infants into strong individuals who can easily overpower and inflict serious injury upon a human.
Remember “Little Mama,” the captive female Nigeria-Cameroon chimpanzee who lived to be in her early 80s? Well, she didn’t come to that Florida safari park on her own volition. She was originally kidnapped from her native Africa, sold into the illicit wildlife trade, exploited for human entertainment as a trained, skating chimpanzee in the traveling Ice Capades show, and when that “career” ended, again found herself in the hands of a wildlife dealer who sold her to the owner of the safari park where she lived her remaining years.
Then there’s Ham, the “space chimp.” Held and trained by the U.S. Air Force, Ham has the unsought distinction of being the first chimpanzee propelled into space on January 31, 1961. Ham had been kidnapped from Cameroon, where he was born in 1957. His plight, and that of other Air Force chimpanzees used in the early days of space research, inspired the creation of the primate protection organization, Save the Chimps.
The earth’s growing climate crisis, an increasingly sinister anthropogenic-caused situation, looms over this diminishing population of rare chimpanzees—and over all of us.
Nigeria-Cameroon chimpanzees are listed in Appendix I 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.
Several protected areas are home to these rare and little-known primates. In Nigeria, these areas include Oluwa Forest Reserve, Gashaka-Gumti National Park, Cross River National Park, and Afi Mountain Wildlife Sanctuary. In Cameroon, these areas include Mbam and Djerem National Park, Korup National Park, Takamanda National Park, Mount Cameroon National Park, Banyang-Mbo Wildlife Sanctuary and the proposed Ebo National Park. Unfortunately, enforcement of wildlife protection laws is difficult to enforce due to inadequate resources. Widespread corruption in the region has only made the task more difficult. As a result, a high level of poaching occurs. Other conservation laws are flouted, too. The logging industry is a major driver of deforestation in Nigeria’s Oluwa Forest Reserve and in Cameroon’s Ebo National Park (which has yet to receive formal protection designation, compounding its vulnerability). Of course, those Nigeria-Cameroon chimpanzees who live outside of these “protected” areas are most vulnerable.
But there is a glimmer of optimism. The region has seen a rise in community-based conservation measures with a focus on chimpanzees, led by local conservation groups. One such group, The SW/Niger Delta Forest Project, is dedicated to preserving highly threatened populations of Nigeria-Cameroon chimpanzees within southwestern and Niger Delta Nigeria. Through conservation-focused research, community education and outreach, stakeholder engagement, and policy advocacy, the Project aspires to preserve these rare primates.
Conservation-focused research includes the study of ecological niche models to predict a species distribution patterns. The Nigeria-Cameroon chimpanzee is an ideal candidate of study, given its genetic and geographic distinctions.
Community education and outreach seeks to foster a sympathetic sentiment, appreciation, understanding, and pride for this endangered primate subspecies and for other resident wildlife.
Stakeholder engagement involves having local communities take on an active role in preserving their forested environment, and by so doing, preserve their chimpanzee citizens. As example, in Nigeria’s Mbe Mountain Range, nine communities have formed a conservation association—resulting in a decline in poaching.
Policy advocacy seeks to negotiate with key decision makers to create new legislation, and enforcement thereof, to ensure the protection and preservation of Nigeria-Cameroon chimpanzees.
The Wildlife Conservation Society (WCS) is another organization working hard to save the Nigeria-Cameroon chimpanzee from extinction. WCS is at the forefront of this mission with support and advocacy for the creation of new protected areas, improved law enforcement, community conservation, education, and awareness, and the creation of alternative livelihoods for local citizens that negate the need for poaching. One innovative approach engages local women’s groups for the cultivation and sale of bush mango.
Written by Kathy Downey, February 2022