CENTRAL CHIMPANZEE

Pan troglodytes troglodytes

Geographic Distribution and Habitat
Central African chimpanzees live in the dense tropical rainforests of Central Africa. These forests are characterized by hot weather and heavy rain. The boundaries of their range are set by the Congo River in the south, the Ubangi River in the east, and the Sanaga River in the north. They are found in the countries of Gabon, Equatorial Guinea, Cameroon, Republic of Congo, Central African Republic, and Democratic Republic of Congo.

Central chimpanzee geographic range. Map credit: Luís Fernández García/Creative Commons

Size, Weight, and Lifespan
Central chimpanzees are the largest of all the chimpanzee subspecies and also exhibit the most significant sexual dimorphism. Males can have a head-to-rump length of up to 38 inches (96 cm) and an average weight of 132 pounds (60,000 g). Females have an average length of 31.5 inches (80 cm) and a weight of 97 pounds (44,000 g).

Chimpanzees can have a wide range of lifespans. Many chimps in captivity have lived to well over 50; however, a more typical life expectancy for a captive chimpanzee is between 30 and 40 years. In the wild, most chimpanzees that survive their infancy will live between 15 and 25 years.

Appearance
Chimpanzees are robust apes with black hair covering most of their bodies. Their bare skin is exposed on their hands, face, and feet. Chimpanzees have pink skin early in life; it turns black as they mature. Central chimpanzees have less hair covering their face than the other subspecies, especially females. Once one looks past the hair, it is easy to see that chimpanzees are our closest relatives, having only diverged from humans 4–8 million years ago. Chimpanzee physiology is not all that different from human physiology.

Central chimpanzees have arms that are not only significantly longer than human arms, but are also the longest of all chimpanzee subspecies. In addition to long arms, their hands feature long fingers and short thumbs adapted for climbing trees. Chimpanzees are too heavy to gracefully climb like the monkeys who inhabit the same areas, but they can climb well enough to forage for the best fruit. Another major difference between humans and chimps is how our legs are built. Human thighs slope inward while chimpanzee thighs slope outward. This allows humans to close their legs together and walk upright, while chimps can only walk upright in short spurts. The chimpanzee foot features an opposable big toe spaced far apart from the other toes allowing them to grasp the branches and maintain balance as they travel through the trees.

Olga Chimp. Photo courtesy of © HELP-Congo. Used with permission

What Does It Mean?

Activity Budget:
A way to quantify animal behavior by observing an animal over an extended period and documenting activity. An activity budget demonstrates how much time an animal spends in various activities such as eating, resting, sleeping, and moving.

Alpha male:
The dominant male animal in a particular group.

Anogenital:
Relating to the anus and genital region.

Estrus:
A recurring period of sexual receptivity and fertility in many female mammals.

Gender dimorphism:
Distinct difference in size or appearance between the sexes of an animal, in addition to difference between the reproductive organs themselves, but only during certain seasons.

Natal group:
The group into which an animal is born.

Polygamous:
Having more than one mate.

Subspecies:
A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

Sympatric:
Occurring or living in the same area; overlapping in distribution.

Visit the Glossary for more definitions

Diet
Chimpanzees, like humans, have a set of teeth that is designed to eat both plants and meat. Fruits make up about 60% of their diet, while leaves make up about 25% of their diet. Seeds comprise about 7% of their diet and the rest is made up of flowers, tree bark, and buds. Meat is a rare but valuable catch for chimpanzees and they will sometimes organize hunts of monkeys and other small animals.

Behavior and Lifestyle
Chimpanzee behaviors change not only with the subspecies, but with individual families as well. This is because many behaviors are passed down from generation to generation as opposed to being totally instinctive. One notable behavior only seen in Central chimpanzees so far is tortoise hunting. Several chimps in Gabon were seen using rocks to crack open tortoise shells.

Daily Life and Group Dynamics 
Chimpanzees are most active during the day. Depending on the season, they will spend somewhere between a third and a half of their time foraging. Activity budgets also show that chimpanzees spend equal parts of of their day socializing, traveling, and resting. Central chimpanzee groups have an average population of about 66 individuals, which is much more than their Western and Nigerian-Cameroon cousins, but much fewer than Eastern chimpanzee groups. A typical group will control a territory of over 7 square miles (18 sq km).

Chimpanzee communities are ruled by an alpha male who must use both strength and diplomacy to maintain his power. Chimpanzee politics are not so different from human politics. Leaders must build and foster alliances, ensure loyalty, and keep a close eye on rivals. Given the right situation, a smart and strong chimp can rule a group for several years.

Fun Facts

Locally, Central African chimpanzees are called “tschegos,” which means laughter. This is also the given name in most older texts

Communication
Chimpanzees may communicate emotions and ideas through noise, displays, contact, or smell. Communication is generally centered around food, threats, and politics. For example, a chimp who is attempting to take over or maintain control of a group will make the loudest noises he can. With his hair standing on end (making himself seem larger), he shouts out barks and hoots while slamming branches and banging his feet on tree trunks.

Thirty-two different vocalizations have been deciphered and researchers are working to learn more. The most famous chimpanzee call is the pant-hoot, which is a series of inhaling and exhaling “hoo-hoo” calls. These calls can be made by chimps finding food, maintaining contact with out-of-sight individuals, and warning others of danger nearby. Other calls may include submission grunts, screams as a distress call, and soft grunts used to stay in contact during foraging.

Visual communication through facial expressions and body language is also common and is well understood by researchers. A chimp who opens his mouth and bares his teeth is frightened, but a chimp who opens his mouth while hiding his teeth is looking to intimidate others. Likewise, an aggressive chimp’s hair may stand on end to make him look bigger.

A chimp may hug, pat, or brush the face of another chimp in an effort to reassure them or calm them down. Submissive individuals may bob their head, bow, or kiss another chimp to show their respect. Many different researchers are studying chimpanzee communication and several guides have been developed to translate their actions.

Reproduction and Family
After a pregnancy of about 8 months, chimpanzees are born totally helpless and unable to support their own weight for their first two months of life. The mother will carry her baby close to her chest for about six months before the baby is strong enough to ride on her back. Over the next two years, the baby will gradually grow more independent and curious. Chimpanzees are fully weaned after about 5 years. It is not uncommon for a young chimp to be prematurely weaned 3 or 4 years into life if his mother gives birth to a new baby in that time. In this case, the older sibling is still cared for, but he may struggle in developing confidence and social skills.

Females are able to mate at some time between 12 and 14 years old while males will likely begin mating at 15 years old. Males tend to stay with their natal group for life while maturing females will leave their group for a new one in what is usually a gradual, months-long process.

Chimpanzees mate year-round. When a female is ready to mate and enters estrus, her anogenital region will swell up. Chimpanzees live in polygamous societies. Any persistent male will find opportunities to father offspring, but males who have higher social rankings tend to be more successful at mating.

Reintroduced chimps. Photo courtesy of © HELP-CONGO. Used with permission.

Ecological Role
Like many fruit-eaters, chimpanzees play a special role in their environment as seed dispersers. Chimpanzees consume the fruit and defecate the seeds elsewhere in the forest. The seeds are then allowed to grow into tree without having to compete with their parents for resources. Chimpanzees are capable of eating far larger seeds than most animals in their ecosystem, and many plant species depend on large animals such as chimps to spread their genes and prosper.

Conservation Status and Threats
The International Union for Conservation of Nature classifies the Central chimpanzee as Endangered (IUCN, 2016) due to their declining population, a trend that is not expected to cease in the next few decades. The IUCN lists their most serious threats as disease, poaching, habitat destruction, and global warming.

Because we are so similar, diseases can transfer from humans to chimpanzee. Many of these diseases are completely alien to chimpanzees and so they have not yet developed any immunity to them. In the past few decades, the Ebola virus has been especially devastating to chimpanzee populations in Central Africa.

Logging in Central African countries has not only harmed chimpanzees through habitat destruction, but it has also made them more accessible for poachers and traders. Until recently, Central chimpanzees have been protected from humans due to the remoteness and density of their environment. These days, logging companies have built roads that poachers may use to reach previously untouchable jungles.

Global warming may prove to be the greatest threat to the Central chimpanzee, as it is the hardest one to combat. As temperatures rise and seasons shift, certain trees will be unable to produce fruit and the food supply for chimpanzees will drastically fall. Additionally, global warming is predicted to shrink the rainforests, increase wildfires, and increase the range of deadly diseases.

Conservation Efforts
The IUCN has adopted an action plan for the years of 2015 to 2025 to aid conservation of the Central chimpanzee as well as the sympatric western lowland gorilla. The plan called for doubling the range of protected forests throughout the region in order to cover 77% of local ape populations. Chimpanzees are relatively slow breeders and developers compared to other animals, and so they need larger habitats and longer time frames for their populations to recover.

One essential action for the conservation of great apes in Central Africa is to expand law enforcement around protected forests and logging areas. Armed guards are hired to protect chimpanzees from poachers, but these guards only cover 22% of their range. Most of the laws needed to protect chimpanzees are already in place in their respective countries; however, they often lack enforcement due to both corruption and logistical reasons.

There must also be an increase in research on the Ebola virus. A vaccine has been developed to protect chimps from Ebola, but it has faced complications related to how it should be tested and administered in the wild. In documentaries, you will often see researchers and crew members wearing face masks. This is meant to prevent the transfer of disease.

The IUCN also calls for more effective land use management to avoid creating patches of forest that can isolate ape populations.

References:

  • https://www.iucnredlist.org/species/15936/102332276
  • http://wwf.panda.org/knowledge_hub/endangered_species/great_apes/chimpanzees/
  • http://www.theprimata.com/pan_troglodytes/
  • https://www.wcs.org/our-work/species/chimpanzees
  • http://pin.primate.wisc.edu/factsheets/entry/chimpanzee/taxon
  • https://alltheworldsprimates.org
  • Pika S, Klein H, Bunel S, Baas P, Théleste E, Deschner T (2019) Wild chimpanzees (Pan troglodytes troglodytes) exploit tortoises (Kinixys erosa) via percussive technology.
  • https://www.nationalgeographic.com/animals/2019/05/chimpanzees-eat-tortoises-smash-shells/
  • https://www.newscientist.com/article/2124022-ebola-vaccine-promising-in-chimps-but-may-never-be-used/

OUR THANKS

Thanks to the Pan African Sanctuary Alliance (PASA) for facilitating securing the beautiful photos on this page on our behalf. PASA is the largest association of wildlife centers in Africa. Their 23 member organizations in 13 countries secure a future for Africa’s primates and their habitat. The combination of PASA’s global network and their members’ local expertise uniquely positions the Alliance to protect chimpanzees, gorillas, bonobos, and monkeys from extinction.

Our thanks to Help-Congo for providing photos for this profile. The HELP project (Ecological Habitat and Freedom of Primates) consists of two partner organizations: HELP Congo and HELP International. HELP Congo is a Congolese association of law 1901, created in 1990. The field of action of this NGO is the protection of primates, particularly chimpanzees, and their habitat. It acts in the Republic of Congo.

Our thanks to Ape Action Africa for supplying photos for this profile. Ape Action Africa is passionate about great ape conservation in Cameroon. They address the immediate threats faced by gorillas and chimps in Africa, and to work with communities to develop long-term solutions to ensure their survival in the wild. Ape Action Africa rescues orphaned and injured gorillas and chimpanzees and works around the clock in Cameroon’s Mefou Primate Park to give them urgent veterinary care and nourishment. When the young orphans are strong enough, they are introduced into groups of their own kind in safe and controlled environments.
 

Written by Eric Starr, August 2019