Chimpanzee

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TAXONOMY

Suborder: Haplorrhini
Infraorder: Simiiformes
Superfamily: Hominoidea
Family: Hominidae
Genus: Pan
Species: P. troglodytes
Subspecies: P. t. schweinfurthii, P. t. troglodytes, P. t. vellerosus, P. t. verus

Other names: common chimpanzee, robust chimpanzee, Western or masked chimpanzee (P.t. verus), Central African or black-faced chimpanzee (P.t. troglodytes), East African or long-haired chimpanzee (P.t. schweinfurthii), Nigeria chimpanzee (P.t. vellerosus); chimpanzé (French); chimpancé (Spanish); schimpans (Swedish)

Conservation status:  Endangered

Life span: 40 to 45 years (wild), up to 60 (captive)
Total population: 200,000 (wild), 1450 (captive)
Regions: Equatorial Africa
Gestation: 8 months (240 days)
Height: 816 mm (M & F)
Weight: 40 to 60 kg (M), 32 to 47 kg (F)

Some argue that chimpanzees should be categorized in the same genus as humans, Homo, based on the fact that chimpanzees and humans diverged only 4 to 6 million years ago (Groves 2001). The implications of changing the taxonomical categorization could have enormous impacts on how chimpanzees are perceived and the rights extended to them. For example, by categorizing chimpanzees as Homo, it might be considered unethical to keep them in zoos or use them in research.

MORPHOLOGY

Chimpanzees exhibit very little morphological differences between subspecies. They have a more robust build than bonobos (Pan paniscus) and are slightly sexually dimorphic with males, on average, weighing 40 to 60 kg (88.2 to 132 lb) and females, on average, weighing 32 to 47 kg (70.5 to 104 lb) (Rowe 1996). Males and females have an average height of 816 mm (2.68 ft) (Rowe 1996).

Common chimpanzee
Pan troglodytes

Chimpanzees are all black but are born with pale faces and a white tail tuft, both of which darken with age. They have prominent ears and both males and females have white beards.

Locomotion patterns include quadrupedal knuckle walking and occasional bipedalism. Chimpanzees are both terrestrial and arboreal, with the amount of time spent on the ground varying between study sites and between sexes (Doran 1996). All chimpanzees build sleeping nests in trees at night (Rowe 1996).

The average lifespan of chimpanzees is 40 to 45 years, though it is considerably longer for captive chimpanzees (Macdonald 2001).

RANGE

CURRENT RANGE MAPS (IUCN REDLIST):
Pan troglodytes

Chimpanzees are found across a west-east belt in equatorial Africa. Their range spans 22 countries: Angola, Burkina Faso, Burundi, Cameroon, Central African Republic (CAR), Congo, Côte d’Ivoire, Democratic Republic of Congo (DRC), Equatorial Guinea, Gabon, Ghana, Guinea, Guinea Bissau, Liberia, Mali, Nigeria, Rwanda, Senegal, Sierra Leone, Sudan, Tanzania, and Uganda (Butynski 2001; Nishida et al. 2001). This represents a total area of about 2.5 million km² (965,255 mi²) though the majority (about 77%) of the total estimated population can be found in only two countries, Gabon and Congo (Cowlishaw & Dunbar 2000). Odzala National Park, Congo boasts the highest population density of chimpanzees in Central Africa with 2.2 individuals per km² (1.37 per mi²) while Gabon has the largest population (Bermejo 1999; Butynski 2001). Researchers roughly estimate the wild population of chimpanzees to be between 100,000 and 200,000 (Nishida et al. 2001). There are approximately 250 animals in zoos and another 1,200 in research facilities (Goodall 2001).

Chimpanzees have been studied at 41 sites, but there are a few long-term study sites and notable scientists that have been sources of invaluable discoveries about chimpanzee biology, society, and culture. In 1960, Jane Goodall began the first long-term study of wild chimpanzees (P.t. schweinfurthii). Her research in Tanzania at Gombe Stream National Park led to significant discoveries about social relationships, tool-use, and warfare in chimpanzee societies. At another site in Tanzania, Toshisada Nishida began a long-term research project on the chimpanzees (P.t. schweinfurthii) of the Mahale Mountains National Park. Christophe and Hedwige Boesch have headed the research on chimpanzees (P.t. verus) in Taï National Park in Côte d’Ivoire since 1976. Other important study sites include Bossou, Guinea and sites in Uganda including the Ngogo study site in Kibale National Park and Budongo Forest Reserve.

HABITAT

Because of their broad distribution, chimpanzees live in a wide variety of habitat types that includes dry savannas, evergreen rainforests, montane forests, swamp forests, and dry woodland- savanna mosaics (Goodall 1986; Fruth et al. 1999; Poulsen & Clark 2004). To live across such different habitat types, chimpanzees must be quite adaptable. In low-altitude rainforests, there is little change in temperature from season to season, the humidity is always high, and there are few dry days each year. In contrast, the arid areas, including the north and southeastern limits of their range (Senegal and Tanzania, respectively), show huge fluctuations in temperature and humidity throughout the year as well as long dry periods (Goodall 1986). Another dry habitat where chimpanzees have been studied is Semliki, Uganda, where average annual rainfall is 1206 mm (3.95 ft) and maximum temperatures reach 34°C (93.2°F) (Hunt et al. 2002).

Characterizations of temperature and rainfall are mostly available for sites where long-term research is being conducted. Gombe and Mahale are similar in climate and character, though Mahale is slightly more humid with more woodlands and higher mountains (Boesch & Boesch-Achermann 2000). Gombe is made up of steep ridges and valleys bordering Lake Tanganyika, one of Africa’s Great Lakes. There is marked seasonality here, with the wet season spanning from mid-October to mid-May, and the rest of the year being quite dry. Daily temperatures range from 18.5°C to 30°C (65°F to 86°F) throughout the year, with August and September being the hottest months (Goodall 1986). Because of the dramatic changes in elevation at Gombe, there are a variety of vegetation types throughout the park: subalpine moorland, open woodland, semideciduous forest, evergreen forest, grassland with scattered trees, and beach (Goodall 1986). At Bossou, the major part of the core area utilized by chimpanzees consists of multi-stage secondary deciduous forest arising in plots abandoned after shifting agriculture. The other areas at Bossou are primary forest and grasslands (Sugiyama & Koman 1987). The chimpanzees at Taï inhabit the only remaining tropical rainforest in Côte d’Ivoire (Boesch & Boesch-Achermann 2000). While there is no true dry season, the rainy seasons are from March to June and between September and November, and the average minimum temperature is 18°C (64°F) (Boesch & Boesch-Achermann 2000).

ECOLOGY

Common chimpanzee
Pan troglodytes

The chimpanzee diet consists mainly of fruit, but they also eat leaves and leaf buds, and the remaining part of their diet consists of a mixture of seeds, blossoms, stems, pith, bark and resin (Goodall 1986). Chimpanzees are highly specialized frugivores and across all study sites preferentially eat fruit, even when it is not abundant. They supplement their mainly vegetarian diet with insects, birds, birds’ eggs, honey, soil, and small to medium-sized mammals (including other primates) (Goodall 1986; Boesch & Boesch-Achermann 1989; Isabirye-Basuta 1989). Their most common mammalian prey is the red colobus monkey (Procolobus badius), though they also eat blue duikers, bushbucks, red-tailed monkeys (Cercopithecus ascanius), yellow baboons (Papio cynocephalus cynocephalus), and warthogs (Boesch et al. 2002). Chimpanzees spend, on average, half of their days feeding, and much time moving from one food source to the next (Goodall 1986). The actual time spent feeding, though, is correlated with the amount of processing time required by the type of food being consumed.

The use of tools to obtain some foods has been documented across all chimpanzee populations. Sticks, rocks, grass, and leaves are all commonly used materials that are modified into tools and used to acquire and eat honey, termites, ants, nuts, and water. While these implements may seem too crude to be considered true tools, there certainly is evidence that forethought and skill are required to make and use them and lack of complexity should not detract from the fact that they are still tools (Boesch & Boesch 1993). For example, to extract honey from the hives of stingless bees, chimpanzees use short sticks stripped of their leaves, twigs, and bark to most effectively scoop it out of the hive. On the other hand, to extract honey from the hives of aggressive African honeybees, chimpanzees use significantly longer and thinner sticks to avoid the painful stings of these bees (Stanford et al. 2000). In a similar fashion, chimpanzees strip the leaves off of long, thin sticks and use these to extract ants from ground nests (Goodall 1986; Boesch & Boesch 1993). This practice requires some amount of skill, and infant and juvenile chimpanzees must practice a great deal before mastering the technique necessary to extract the ants still clinging to the thin, flexible tools. In fact, some chimpanzees never fully master the skill of ant dipping, and in general, females are more successful than males in this endeavor (Goodall 1986; Boesch & Boesch 1993). A similar tool and technique is used to extract termites from nests at Gombe, but at Taï, the chimpanzees simply use their hands (Boesch & Boesch 1993).

Common chimpanzee
Pan troglodytes

Using a hammer and anvil tool set made of fallen branches or hand-held stones and exposed tree roots or rocky outcroppings, chimpanzees in West Africa crack hard nuts (Boesch & Boesch 1993; Boesch & Boesch-Achermann 2000). Often these items are not found together or near a source of nuts, so nut-cracking chimpanzees must exhibit forethought to gather the appropriate accoutrements to eat these important high-protein, high-fat foods. Like ant fishing, nut cracking is a skill that must be learned, and infants and juveniles must learn from their mothers the appropriate tools and movements to shell nuts (Boesch & Boesch-Achermann 2000). Chimpanzees also use leaves as sponges or spoons to drink water. Selectively choosing the type of leaf to use, chimpanzees crumple these leaves in their mouths and then submerge them in water; the crumpled leaves act like a sponge and they suck the water out of them and repeat the process (Sugiyama 1995). This behavior is especially prevalent where water is scarce at certain times of year and it is so deep in tree holes that chimpanzees cannot easily access it directly with their mouths.

Chimpanzees have excellent mental maps of their home ranges and use these to locate food resources repeatedly. Their attention may be directed to a new food source by a noisy group of animals, such as birds or other primates, or they may be led to a new fruit tree or termite mound by a foraging companion that has been there before (Goodall 1986).

Long thought to be free of natural predators because of their large body size, work in the Taï Forest and at Lopé National Park, Gabon has shown that leopard (Panthera pardus) attacks can be a significant cause of mortality in chimpanzees (Boesch &Boesch-Achermann 2000; Henschel et al. 2005). The extent to which leopards choose to hunt chimpanzees is unclear, though, and may be the work of just a few risk-taking cats (Boesch & Boesch-Achermann 2000). Lions are also capable of killing chimpanzees, and predation by lions has been observed at Mahale Mountains National Park in Tanzania, but there are scant observations of lion predation at other sites where they are sympatric with chimpanzees (Tsukahara 1993).

Content last modified: April 13, 2006

Written by Kristina Cawthon Lang. Reviewed by Elaine Videan.

Cite this page as:
Cawthon Lang KA. 2006 April 13. Primate Factsheets: Chimpanzee (Pan troglodytes) Taxonomy, Morphology, & Ecology . <http://pin.primate.wisc.edu/factsheets/entry/chimpanzee>. Accessed 2020 July 30.

SOCIAL ORGANIZATION AND BEHAVIOR

Primate behavioral ecologists have long debated the costs and benefits of group living, but some of the factors that affect chimpanzee social structure include decreased likelihood of predation, resource defense and feeding efficiency, and higher copulatory success because of access to mates (Sakura 1994; Boesch 1996). Chimpanzees live in a fission-fusion social group consisting of a large community that includes all individuals that regularly associate with one another (up to a few hundred individuals) and smaller, temporary subgroups, or parties. These subgroups are unpredictable and can be highly fluid, changing members quickly or lasting a few days before rejoining the community (Goodall 1986; Chapman et al. 1993; Boesch 1996). At Taï, the average party size is between five and eight individuals (Boesch 1996). Party size greatly increases when food availability increases, though, and at Kibale, average party size is 10 but ranges from one to 47 individuals during periods of highest food availability (Mitani et al. 2002). Party size also increases when the estrous females are present (Matsumoto-Oda et al. 1998; Mitani et al. 2002). Party composition is variable, including unisexual and bisexual parties of adolescents or adults, parties of adult females and infants, lone adult females and their offspring, and mixed age and sex parties (Boesch 1996). The most frequently observed party across all chimpanzee communities is the mixed-sex party, though Taï males are the most inclined to associate with females, and Gombe males are the least inclined to do so. At Bossou, though, where the adult sex ratio is skewed, the high number of females relative to males means the most common party composition there is mother-infant (Boesch 1996).

Common chimpanzee
Pan troglodytes

There is a distinct linear dominance hierarchy in male chimpanzees, and males are dominant over females (Goldberg & Wrangham 1997). Males remain in their natal communities while females, in general, emigrate at adolescence, between nine and 14 years old (Nishida et al. 2003). The complete transition between groups may take up to two years, though, and is characterized by vacillating between their natal group and new community (Goodall 1986; Hasegawa 1989; Pusey 1990). Rates of female transfer are much higher at Mahale and Taï than at Gombe and Bossou. This may be attributed to the smaller population size and isolated conditions at Gombe and Bossou; with fewer options, it is more beneficial to remain in their own group and take behavioral precautions to avoid inbreeding (Goodall 1986; Gagneux et al. 1999; Nishida et al. 2003). For female chimpanzees that do emigrate, though, they are not likely to be related to other adult females in their new community and the dominance hierarchy is linked to age (with younger immigrant females ranking the lowest) and the status of their offspring (Nishida 1989). Lactating females generally spend most of their time with their own offspring, though they may be seen with other lactating females in “nursery groups” (Pepper et al. 1999). Females become very sociable during estrus, though, and are seen mostly in bisexual parties (Pepper et al. 1999).

Given the female-biased dispersal pattern, male chimpanzees in a community are more likely to be related to one another than females are to each other, but matrilineal kinship does not always strongly influence patterns of male chimpanzee social behavior. In studies at Kibale, genetic analyses of males support the theory that cooperation is of greater evolutionary significance than kinship affiliation (Goldberg & Wrangham 1997; Mitani et al. 2000). Research at Gombe, on the other hand, has consistently emphasized kinship as the most important underlying factor of the strong social bonds (Goodall 1986). Close relationships between males serve two purposes within chimpanzee communities: inter-community interactions and intra-community politics (Goldberg & Wrangham 1997). Some examples of inter-community interactions include hostile attacks by groups of males and cooperative boundary patrol parties. Intra-community interactions that are dominated by male cooperation include securing and maintaining dominance, mate guarding, and group hunting and meat sharing (Goldberg & Wrangham 1997; Mitani et al. 2000).

First seen at Gombe in 1963, chimpanzee hunting behavior probably evolved because of the direct benefits of a protein source in their largely frugivorous diets, but it is more than nutritionally important; meat is socially important as well (Mitani & Watts 2001). Meat is social currency used to develop and maintain alliances between adult males; it is usually shared reciprocally and non-randomly (Mitani & Watts 2001). Hunting is cooperative in the sense that multiple males are involved in cornering and capturing prey, though there is debate among researchers if this is true cooperation (Videan pers. comm). Members of the hunting party are spread out widely on the ground and in the trees (if hunting arboreal prey such as colobus monkeys), and other members of the community often observe and vocalize excitedly throughout the pursuit (Watts & Mitani 2002). Hunting success increases with group size, and chimpanzees are more successful where the canopy is broken and open. The male chimpanzees in Kibale are the most successful hunters with an average success rate of 84%, though at other sites hunting parties have success rates above 50% (Watts & Mitani 2002). The influence on red colobus (Procolobus badius) populations because of high success rates of chimpanzee hunters should not be ignored. Chimpanzees are contributing to population declines of red colobus monkeys in multiple sites across Africa, especially at Gombe (Struhsaker 1999).

REPRODUCTION

Males reach adolescence between nine and 15 years of age and are capable of reproduction at 16 years or older. First estrus is seen in females at 10 years of age and is characterized by anogenital swelling. Menarche occurs a few months after the first swelling and continues on a cycle of about 36 days (Goodall 1986). There is a period of adolescent infertility in female chimpanzees that usually coincides with permanent emigration from their natal groups (Goodall 1986; Nishida et al. 2003). During the transition period, females still exhibit sexual swellings that may serve as a passport to gain males’ tolerance in their new social communities (Boesch & Boesch-Achermann 2000). Once established in their new communities, young females cease cycling for two to four years but continue to attract adult males and mate promiscuously. First parturition occurs, on average, between 13 and 14 years and the interbirth interval is between three and five years (Goodall 1986; Boesch & Boesch-Achermann 2000; Nishida et al. 2003). The lag time between menarche and first parturition may have adaptive significance for emigrating females. Having offspring before being accepted by the community could jeopardize both the mother and infant (Boesch & Boesch-Achermann 2000). Infanticide has been documented at Gombe, Mahale, and Kibale study sites and is often attributed to sexual selection theory; males kill infants unlikely to be their own, infanticide shortens interbirth intervals by inducing cycling in females that lose infants, and infanticidal males thus increase their chances of siring offspring. Infanticidal behavior by females has also been observed, though there is some question as to whether these were isolated incidences of pathological behavior, or if it could be related to dominance rank in females (Goodall 1986; Pusey et al. 1997).

Common chimpanzee
Pan troglodytes

Mating occurs throughout the year and there is no evidence of a birth season, female chimpanzees do exhibit seasonality in the number of estrous females within a group (Wallis 1995; Boesch &Boesch-Achermann 2000; Wallis 2002). The number of estrous females is positively related to food abundance; because of the energetic requirements of ovulation and mating, female chimpanzees are more likely to come into estrus during times when food is readily available (Anderson et al. 2006). The majority of chimpanzee reproductive behavior is promiscuous, with females mating with multiple males opportunistically during estrus, though the majority of copulation occurs during the 10-day period of maximal tumescence (Goodall 1986). There are other types of reproductive strategies that are recognized as well. Restrictive mating, where the dominant male restricts other males from mating with estrous females in the community, consortship mating, where an adult pair leave the community for several days to weeks, and extra-group mating, where females leave their communities and mate furtively with males from nearby communities (Goodall 1986; Gagneux et al. 1999). Chimpanzee social and mating groups do not always overlap, given the variety of reproductive situations. This may have evolved because females have limited choice in mates after committing to a community, and the dominance hierarchy of males often dictates which males an estrous female will mate with. By having multiple strategies, females can expand the pool of males from which they choose while not losing the important support of the males in their communities (Gagneux et al. 1999). Having multiple strategies also maximizes the chances of males’ reproductive success; they are able to vary, throughout their lives, their mating strategies with depending on their position in the dominance hierarchy.

PARENTAL CARE

In chimpanzees, the majority of parental care is the responsibility of the mother and is critical to the survival and emotional health of youngsters (Goodall 1986). Chimpanzee infants and juveniles benefit from the close relationship with their mothers in terms of food, warmth, protection, and the opportunity to learn skills. There is also some evidence that a young chimpanzee achieves rank according to his or her mother’s status (Goodall 1986; Boesch & Boesch-Achermann 2000).

Chimpanzee newborns and mothers are in constant ventral-ventral contact for the first 30 days of life. During the newborn period, chimpanzees are helpless to survive without maternal support and though they have a firm grasping reflex, it is not strong enough to support the infant for more than a few seconds at a time. In fact, for the first two months of life, chimpanzees are unable to support their own weight and depend entirely on their mothers’ support (Bard 1995). After five or six months, chimpanzee infants ride dorsally on their mothers’ backs. During the first year of life, infant chimpanzees maintain almost continual contact with their mothers. By the age of two, they begin to travel and sit independently within five meters of their mothers and this corresponds to a decrease in nursing and the onset of independent eating and play behavior (Bard 1995; Coe 1990). Not until three years of age do young chimpanzees venture more than five meters from their mothers, and between ages four and six, the period of infancy ends with weaning (Bard 1995).

During the juvenile period, from about six to nine years old, chimpanzees remain close to their mothers but play independently and have greater social interactions with other community members. Adolescent females spend some of their time moving between groups and are supported by their mothers during agonistic encounters while adolescent males spend more time with adult males in social activities such as boundary patrols and hunting parties (Bard 1995).

COMMUNICATION

Common chimpanzee
Pan troglodytes

Visual and vocal communication are important to chimpanzee society. A suite of facial expressions, postures, and sounds function as signals during interactions between individuals and groups (Goodall 1986). Chimpanzees have particularly expressive, hairless faces and facial expressions play an important role in close-up communication between individuals. For example, a “full closed grin” is in response to an unexpected and frightening stimulus and evokes an instant fear response in others. Other facial expressions include “lip flip,” “pout,” “sneer,” and “compressed-lips face” (Goodall 1986). Body position and stance also convey information to other individuals. Submissive positions include extending the hand, crouching, and bobbing while aggressive positions usually involve an individual trying to appear larger than he is by swaggering bipedally, hunching his shoulders, and waving his arms (Goodall 1986). Adult chimpanzees will also drum on the trunks of trees, by beating their hands and feet against large trees, for a dramatic display. Drumming can be heard in multiple contexts including while traveling, during displays, encounters with other chimpanzee communities, and when arriving at large food sources (Crockford &Boesch 2005).

LISTEN TO VOCALIZATIONS

Vocal communication also conveys a wide variety of emotional states and intentions and often serves to affect the behaviors of those that hear the calls. One important vocalization is the “pant-hoot,” which is the most commonly heard call of adult individuals and is used to signify food enjoyment, social excitement, and sociability feelings (Goodall 1986). One of the best ways to assess dominance rank is to listen for “pant-grunts,” which are directed towards dominant individuals by submissive individuals (Goodall 1986; Pusey et al. 1997). Distance calls are used to draw attention to danger or food sources for other community members as well as establish location of other groups in the area (Goodall 1986). It is given while feeding, during travel, and when meeting chimpanzees from other parties or communities (Crockford & Boesch 2005). The “pant-hoot” is a four part call which starts with soft “hoos” and increasing in volume as the “hoos” build up to the climax of the call, made up of screams and sometimes barks, followed by the ending, in which the screams die down to soft “hoos” again (Crockford &Boesch 2005). Another call heard under these circumstances is the “bark” which is modified under certain circumstances as the “short bark,” when hunting and the “tonal bark,” given in the presence of large snakes (Crockford &Boesch 2005).

SPECIAL NOTES

Highly distinctive behavioral differences between populations of chimpanzees have been observed and documented. These behavioral differences between communities include 39 different patterns of tool-use, grooming, and courtship behaviors and are classified as cultural differences (Whiten et al. 1999). Behaviors are classified as culture if inter-generational transmission of behavior occurs through social or observational learning to become a population level characteristic. That is, these behaviors are not linked to genetic differences among subpopulations nor are they related to ecological differences between study sites. While some behaviors are species typical, such as nest building, others are far from uniform across chimpanzee populations. Termite or ant fishing, which may be the most famous examples of chimpanzee tool use are seen only in some populations while nut cracking behavior is seen only in West Africa (McGrew 1994; Whiten et al. 1999).

Content last modified: April 13, 2006

Written by Kristina Cawthon Lang. Reviewed by Elaine Videan.

Cite this page as:
Cawthon Lang KA. 2006 April 13. Primate Factsheets: Chimpanzee (Pan troglodytes) Behavior . <http://pin.primate.wisc.edu/factsheets/entry/chimpanzee/behav>. Accessed 2020 July 30.

 

INTERNATIONAL STATUS

CITES: Appendix I (What is CITES?)
IUCN Red List: P. troglodytes: EN (What is Red List?)
Key: EN = Endangered
(Click on species name to see IUCN Red List entry, including detailed status assessment information.)

Common chimpanzee
Pan troglodytes

With only 100,000 to 200,000 left in the wild and about 250 individuals in zoos in the United States, chimpanzees are among the most threatened primates in Africa for many reasons (Goodall 2001). Central chimpanzees are the most numerous, with about 80,000 found in Gabon and Congo, eastern chimpanzees number about 13,000 though the estimates from DRC are very rough, and western chimpanzees are very patchily distributed with no more than 12,000 remaining (Oates 1996). Several synergistic factors have led to the decrease in chimpanzee populations across Africa and some of the most salient threats include hunting, habitat loss and degradation due to industrialized logging and human population growth, and disease (Kormos 2003; Walsh et al. 2003; Poulsen & Clark 2004). Even in Gabon and Congo, widely considered stronghold countries for chimpanzees, populations are declining at a rate of at least 4.7% per year (Walsh et al. 2003).

CONSERVATION THREATS & POTENTIAL SOLUTIONS

Threat: Human Induced Habitat Loss and Degradation

Deforestation in the tropics has multiple causes including agricultural expansion, overgrazing, fuelwood gathering, commercial logging, and infrastructure and industrial development (Rowe et al. 1992). Particularly problematic in Africa is industrialized logging, which compromises the habitat in which chimpanzees thrive, both directly and indirectly. Direct consequences of logging include the loss of trees, but the indirect threats are more far reaching and include soil erosion, loss of biodiversity, climate change, desertification, watershed degradation, landscape fragmentation due to roads, and facilitation of access by settlers who convert logged forest into agricultural areas (Rowe et al. 1992; Wilkie et al. 2000). The roads that are created are particularly of concern because they provide access to once isolated forests that can then be exploited for resources, both floral and faunal.

Human population growth is another underlying factor of wild chimpanzee vulnerability. With population growth rates increasing, food production miserably inadequate, and political and economic insecurity a fact of life, Africans are struggling to meet short-term needs at the expense of chimpanzees (Butynski 2001). Demand for land for housing, development of infrastructure, agriculture, and grazing animals indirectly threatens chimpanzees because of forest loss. The need for forest products for subsistence usage such as vines for basketry, medicine, collection of food, and firewood also degrades chimpanzee habitat (Conserving the Chimpanzees of Uganda 1997). As human populations explode so will the development of infrastructure and habitat degradation will follow. Currently, more than 70% of chimpanzee habitat is affected by infrastructure and if current human population growth rates are maintained, it is estimated that by the year 2030 less than 10% of chimpanzee habitat will remain unaffected by development (Nellemen & Newton 2002).

Potential Solutions

Some possible suggestions to mitigate habitat degradation due to logging include responsible forest practices, including selective felling, use of pitsaws rather than power saws, and restrict access for loggers to only a few days per week (Endroma et al. 1997). Sustainable forestry practices that include selective logging and limited extraction can not only stop negative effects of logging on chimpanzee populations, but actually improve population densities because of higher abundance of fruits in successional plots and a decrease in mechanized logging equipment (Plumptre and Grieser Johns 2001). Establishment of strict protection areas in high priority conservation areas thereby precluding logging activity is another possible mechanism to decrease habitat loss. This solution is only possible, though, if alternative income strategies are provided for the communities that depend on logging for income.


Threat: Invasive Alien Species

As humans come into contact with chimpanzees more readily through bushmeat availability and open-access logging roads, the spread of zoonotic diseases such as Ebola, a deadly hemorrhagic fever, threaten both human and ape populations. In some areas, Ebola is a concern for the viability of chimpanzee populations because of its acute deadliness and misunderstood etiology (Walsh et al. 2003). Other infectious diseases that threaten chimpanzees include the common cold, pneumonia, paralytic poliomyelitis, tuberculosis, chicken pox, and influenza (among others) (Butynski 2001). An epidemic of any of these diseases could cause massive mortality within a small population and potentially cause rapid extinction of subspecies and species. In 1966, multiple infants were killed and many adults paralyzed in an outbreak of a paralytic disease (probably polio) at Gombe (Goodall 1986). Frequent close contact due to increasing human populations or even tourists, guides, and park personnel may increase the risk of transmitting these diseases to chimpanzees, and the problem could worsen.

Potential Solutions

Limiting human proximity to chimpanzees as much as possible will decrease the likelihood of infectious diseases traveling between humans and chimpanzees. In areas of high tourism, research activity, and where interactions between chimpanzees and local communities are common, stricter precautions are needed to protect chimpanzees from human diseases as well as safeguard humans against novel chimpanzee diseases (Butynski 2001). For tourists and researchers that come into close contact with chimpanzees, certain regulations should be implemented and adhered to including regular screening for and vaccination against diseases such as tuberculosis and proper sanitation including hand-washing, disinfectant footbaths, or surgical masks within a certain distance of the apes.


Threat: Harvesting (hunting/gathering)

Though the trade of chimpanzees is restricted, the unstable political situation and rampant corruption in many countries translates into little enforcement (Ammann 2001). The increase in availability of firearms over the last few decades has greatly increased poaching efficacy. The prevalence of guns in poaching activity is 80% greater than other weapons (including traps, spears, and harpoons) (Poulsen & Clark 2004). Modern firearms make poaching these large, strong apes much easier and more successful than when using traditional weapons. For hunters that poach chimpanzees for commercial purposes, the use of guns ensures a higher yield as well, so populations may be dropping exponentially faster than if traditional weapons were used. Moreover, because of their life history characteristics, chimpanzees are more likely to go extinct due to hunting than other primates. Those primates most vulnerable to hunting pressures are those dependent on old-growth forest, that weigh at least 4 kg (8.82 lb), spend a significant amount of time on the ground, are noisy and conspicuous, and live in areas of high or increasing human populations that have a tradition of hunting primates or where a demand for bushmeat exists (Struhsaker 1999). Especially troubling is the problem of orphaned chimpanzees. Poachers are only interested in adults for their meat, but killing an adult female with dependent offspring ensures that those infants or juveniles will either be sold into the pet trade or die because they lack the support of their mother so integral to chimpanzee development.

Another factor that has made hunting easier is the spread of industrialized logging. Commercial logging transforms roadless forests into major thoroughfares which can be easily accessed by commercial hunters. Poachers can find their own transportation or hitchhike on logging trucks into the forests and loggers, after their daily work, can stay to hunt before driving back to the village (Ammann 2001). Not only does the infrastructure provided create ease of access to forests for poachers (including restricted natural areas and parks), but an influx of men working for logging companies drives up the demand for bushmeat, which is much less expensive than other protein sources available at markets in logging towns (Walsh et al. 2003). More than just providing access to areas where chimpanzees are available, logging companies provide guns, materials for snares, transportation to and from hunting areas as well as transportation of carcasses to markets in large cities. Employees of some logging companies are involved at every step of the bushmeat process from the tools to make the guns to the consumption of the meat (Ammann 2001).

Potential Solutions

If the bushmeat trade is to stop, there are some very important and difficult objectives that must be achieved. First, the governments of African countries have to implement sustainable use policies for the natural resources in their countries and global institutions such as the World Bank must begin to offer financial and political incentives to implement environmentally responsible development projects that do not include the unsustainable use of natural resources (Butynski 2001). These projects should include the development of alternate food sources for bushmeat.

Furthermore, logging companies should be held to corporate codes of conduct and responsibility by western consumers. Logging companies with leases to forests are usually from developed countries; certainly international pressure on these companies could be great enough to change some of their policies. Certification programs based on sustainable techniques and extraction practices are another option to decrease bushmeat hunting (Butynski 2001). Reviewed by independent parties, the criteria of certification can involve control of the bushmeat trade and maintenance of biodiversity as central parts of the accreditation process. Education programs and materials at zoos and on the internet can get the message across to western consumers that purchasing uncertified tropical woods from Africa has deleterious effects on biodiversity, chimpanzee habitat, as well as the people of Africa.

Another step for African governments is to turn so-called “paper parks” into legitimate protected areas. Enforcement of protected areas and the laws regarding the trade of chimpanzees would also affect the number of chimpanzees killed for bushmeat. Guards and park patrols are needed to deter hunters from entering protected areas in search of chimpanzees.

Finally, sanctuaries for orphaned chimpanzees are necessary to rehabilitate the infants and juveniles and save them from an unnatural life in a home. Chimpanzee orphanages, while not ideal for developing chimpanzees, could ensure a relatively normal socialization and learning period, and eventually orphaned chimpanzees may be returned to the wild or be used in captive breeding programs, if necessary.

For more reading about the bushmeat crisis and commercial logging: Peterson D. 2003. Eating apes. Berkeley, CA: Univ Calif Pr. 320 p.
http://www.bushmeat.org
http://www.karlammann.com


Threat: Accidental Mortality

Across much of their range chimpanzees are threatened by snares set by poachers and farmers. Though snares do not kill adult chimpanzees immediately, wounds caused by snares can become infected or snares can disfigure chimpanzees to the point that they can no longer obtain and eat food (Endroma et al. 1997; Quiatt et al. 2002; Reynolds et al. 2003). In Kibale, snares injure chimpanzees at a rate of 3.7 percent per year, and though chimpanzees have learned to recognize snares, they often are caught when their attention is distracted (Wrangham 2001).

Potential Solutions

Guards and patrols in parks and protected areas that survey and disarm snares and traps could decrease accidental mortality. Habituated chimpanzees in field research groups could receive basic medical treatment, including antibiotics, for infected wounds, if necessary, though immobilization of chimpanzees for veterinary treatment is often difficult and dangerous (Wrangham 2001).


Threat: Persecution

As alluded to above, where chimpanzees coexist with humans that practice agriculture, these apes may be considered pests, raiding crops, and in a few, very rare instances, killing children (Endroma et al. 1997; Wrangham 2001; Reynolds et al. 2003). Pest chimpanzees are often killed by farmers and then sold for profit or fed to their hunting dogs (Wrangham 2001).

Potential Solutions

Given the growing human population across Africa, it is unlikely that human-chimpanzee conflict will decrease. Therefore, the best solution to increase tolerance of chimpanzees and decrease their persecution in areas where humans and chimpanzees coexist is to make them valuable to the local people through ecotourism and research (Wrangham 2001). Though neither solution is perfect and both have risks and benefits, both offer an opportunity for local people to fiscally benefit from the presence of chimpanzees and thereby increase their tolerance of crop-raiding behavior. Either directly through employment or generating revenues to reimburse people for crops lost to chimpanzees, ecotourism and research programs change the attitudes of people towards chimpanzees and increase their acceptance as these apes begin to “pay for themselves.”


Threat: Changes in Native Species Dynamics

Though it is not well documented, the potential exists for parasitic or pathogenic infections to cause massive mortality in chimpanzee populations (Butynski 2001). Over 100 parasitic diseases, including protozoal and metazoal pathogens, affect the great apes and they are fatal or cause morbidity with severe consequences for behavior and reproduction. Often mortality results from a secondary infection in lesions caused by the primary pathogen (Toft 1986).

Potential Solutions

In some field sites where chimpanzees are habituated, it is possible to administer antibiotics for these and other diseases, which may mitigate the effects but do not eliminate the source or prevent recurrent infections (Goodall 1986).


Threat: Intrinsic Factors

Some intrinsic factors, shaped by human-induced environmental changes, threaten chimpanzee populations. High juvenile mortality and sex differences in mortality threaten recruitment slow population growth rates (Hill et al. 2001). Factors that contribute to high mortality in wild chimpanzees include poor nutrition, lack of regular veterinary health care, and natural hazards such as predators and conspecific aggressiveness. Moreover, because of their long lifespan and reproductive characteristics, a female chimpanzee is expected to produce only .8 daughters, on average, in her entire lifetime (Hill et al. 2001). This is well below the population replacement rate, and even a slight change in population composition, caused by diseases, habitat fragmentation, or poaching could negatively affect growth rate, causing extirpation.

Inbreeding necessitated by habitat fragmentation could also pose a threat to chimpanzee conservation. Strategies of inbreeding avoidance are evident in the mating behavior of female chimpanzees; they often seek extra-group copulations and actively avoid mating with close community members. Habitat fragmentation could isolate female chimpanzees and either force them to mate with community members that may be related to them or even inhibit successful dispersal from their natal communities (Gagneux et al. 1999). The potential problems associated with inbreeding are particularly devastating in small communities and include inbreeding depression and genetic drift (Marsh 2003).

Potential Solutions

Intrinsic factors which threaten chimpanzees that are compounded by human influence such as inbreeding depression due to habitat fragmentation and high juvenile mortality due to zoonotic disease transfer should be the focus of conservation programs. Creating habitat corridors to increase gene flow between populations and increasing the number protected areas could help decrease the possibility of inbreeding while providing supportive veterinary care to sites where habituated chimpanzees are found may alleviate undue suffering from diseases transferred from local human populations.


Threat: Human Disturbance

Much time and energy has been devoted to habituating chimpanzees at some research sites in Africa. Where they have been studied for great lengths, chimpanzees are accustomed to humans, and while this is helpful for researchers, it also poses a risk to the apes’ health. Moreover, where chimpanzees have not been habituated to human presence but researchers have tried to habituate them, the most common response is curiosity and trust of humans (Tutin & Fernandez 1991; Morgan & Sans 2003). Chimpanzees that are accustomed to humans or are not afraid of them on first contact are vulnerable to poaching and diseases.

War and civil unrest is, unfortunately, relatively common in post-colonial Africa. The effects of political instability and conflict on wildlife, especially chimpanzees, should not be underestimated. In Rwanda, for example, civil war starting in 1990 directly affected the chimpanzees because of landmines and mortars in the forests, while the indirect consequences were habitat degradation due to the massive number of people seeking refuge in protected forests and withdrawal of funding for conservation projects and research (Plumptre et al. 2001).

Potential Solutions

It is enormously important that research, including direct observation, continues on chimpanzees. Current field research practices are non-invasive and there is little evidence that field workers’ presence disturbs chimpanzees’ social or physiological patterns, still the risks of exposure to disease and trust of humans may threaten chimpanzees. If chimpanzees are habituated at a field site, much effort should be focused on physically protecting that area and keeping it free of poachers as well as precautionary measures to ensure the subjects are not exposed to infectious diseases.

While intractable ethnic divisions lead to instability and conflict in many African nations, there are a few things that can be done to minimize damage to protected areas and conservation projects during future times of instability. When possible, researchers should maintain a presence of committed staff at the project site, ensure continued funding through continued research, plan ahead for unsafe conditions, train junior staff thoroughly, maintain neutrality, and provide good communication systems between field sites and elsewhere (Plumptre et al. 2001).

The threats to chimpanzee survival are closely linked and it will take much effort to create solutions to these problems. The economic atmosphere in many of the chimpanzee range countries serves to fuel hunting and logging (Wilkie et al. 2000). Unfortunately, the problems of scarce economic opportunity, political strife, and civil unrest, are too complicated to be solved before chimpanzee populations are annihilated. Ecotourism is not a viable income-earning alternative because of the civil conflict in certain regions of Africa. Because ecotourism is not a reliable solution to the continuous decline of chimpanzee populations, conservationists should invest in massive law enforcement campaigns to guard parks and other formally protected areas from poachers (Walsh et al. 2003). Other options are to focus on areas where high densities of chimpanzees occur naturally and human populations are currently scarce, for example, the swamp forests of Congo. In these areas, chimpanzees utilize swamp forests during the dry season and terra firma during the wet season, but human population density is low because of the difficulty of access, low timber values in the area, and few agricultural possibilities (Poulsen & Clark 2004). Protection of swamp forests would be simple and effective during the wet season and because of the limited access to gathering areas during the dry season, it would be easy to protect large numbers of chimpanzees at other times of the year.

LINKS TO MORE ABOUT CONSERVATION

CONSERVATION INFORMATION

CONSERVATION NEWS

ORGANIZATIONS INVOLVED IN Pan troglodytes CONSERVATION

Content last modified: April 13, 2006

Written by Kristina Cawthon Lang. Reviewed by Elaine Videan.

Cite this page as:
Cawthon Lang KA. 2006 April 13. Primate Factsheets: Chimpanzee (Pan troglodytes) Conservation . <http://pin.primate.wisc.edu/factsheets/entry/chimpanzee/cons>. Accessed 2020 July 30.

The following references were used in the writing of this factsheet. To find current references for Pan troglodytes, search PrimateLit.

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Content last modified: April 13, 2006

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