Pan troglodytes ssp. verus 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Primates Hominidae

Scientific Name: Pan troglodytes ssp. verus Schwarz, 1934
Parent Species:
Common Name(s):
English Western Chimpanzee
Taxonomic Source(s): Mittermeier, R.A., Rylands, A.B. and Wilson D.E. 2013. Handbook of the Mammals of the World: Volume 3 Primates. Lynx Edicions, Barcelona.
Taxonomic Notes:

Chimpanzee taxonomy remains an active area of research. Four subspecies are commonly recognized: the Western Chimpanzee (Pan troglodytes verus), the Nigeria-Cameroon Chimpanzee (P. t. ellioti), the Central Chimpanzee (P. t. troglodytes), and the Eastern Chimpanzee (P. t. schweinfurthii). Although the appropriate taxonomic labelling for different Chimpanzee populations remains a matter of debate (e.g., Prado-Martinez et al. 2013, Fünfstück et al. 2015), some genetic research suggests that currently recognised subspecific distinctions are warranted (e.g., Becquet et al. 2007, Gonder et al. 2011). Given that the different populations across Africa differ in the threats they face, a regional approach is valuable for conservation purposes. Therefore, we use a four-subspecies classification, acknowledging that future work may lead to recognition of more or fewer subspecies.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A4bcd ver 3.1
Year Published: 2016
Date Assessed: 2016-03-18
Assessor(s): Humle, T., Boesch, C., Campbell, G., Junker, J., Koops, K., Kuehl, H. & Sop, T.
Reviewer(s): Williamson, E.A. & Mittermeier, R.A.
Contributor(s): Blom, A., Brugiere, D., Butynski, T.M., Casanova, C., Duvall, C., Ellis, C., Farmer, K., Fleury-Brugiere, M., Gamys, J., Granier, N., Herbinger, I., Kormos, R., Kouakou, C., Normand, E., N'Goran, P., Oates, J.F., Phillips, K., Pruetz, J., Regnaut, S. & Wild Chimpanzee Foundation
Due to high levels of poaching, and loss of habitat and habitat fragmentation resulting from human activities, Pan troglodytes verus is estimated to have experienced a significant population reduction in the past 50 years, and it is suspected that this reduction will persist in coming years. An analysis by Sop et al. (in prep.) estimated an average annual rate of decline of 6.53% between 1990 and 2014. This rate was derived from models of decline across 20 sites, where at least two surveys were carried out during this time period. Some populations remained stable; others experienced dramatic declines. Using a total population estimate of 35,000 individuals in 2015 (Sop et al. in prep.) and assuming variable but conservative rates of annual decline of 1% for the period 1960–1989, 4.5% for 1990–2014, and then halving that rate to 2.25% for 2015–2029 (assuming that conservation efforts in coming years will be able to reduce rates of decline), the total population loss over a three-generation period (i.e., 69 years; Western Chimpanzee generation time is taken to be ~23 years) is estimated to exceed 80%, hence qualifying this taxon as Critically Endangered under criterion A.

The causes of the reduction, although largely understood, have certainly not ceased and are not easily reversible. Current trends in threat patterns are very concerning. The extent of overlap between Chimpanzee occurrence and areas suitable for oil-palm development is likely to exacerbate population declines in coming years (Wich et al. 2014), especially in Liberia (94.3% overlap) and Sierra Leone (84.2% overlap), which along with Guinea are the strongholds for the taxon (Kormos, Humle et al. 2003, Brncic et al. 2010, Tweh et al. 2015). This situation is even more concerning as the majority of Chimpanzees in these three countries occur outside protected areas. The suspected future continuation of population reduction is, therefore, a precautionary approach based on industrial development trends and associated infrastructure, especially in Guinea and in post-war Liberia and Sierra Leone. The decline in Western Chimpanzees numbers is also linked to increasing human populations and movements, habitat loss and fragmentation, the high risks of zoonosis and disease outbreaks, the persistence of an illegal pet trade and the high degree of political instability in some range states.
Previously published Red List assessments:

Geographic Range [top]

Range Description:

Pan troglodytes verus (Schwarz 1934) is found in West Africa, and is patchily distributed from Senegal to Ghana. It is possible that its geographic range extends further east, but genetic evidence is needed to confirm whether or not P. t. verus occurs in western Nigeria. In high altitude parts of their range, western chimpanzees are found up to 1,200 m asl (Koops et al. 2012), and occasionally go beyond 1,300 m asl (K. Koops pers. comm. 2016).

Countries occurrence:
Côte d'Ivoire; Ghana; Guinea; Guinea-Bissau; Liberia; Mali; Senegal; Sierra Leone
Possibly extinct:
Benin; Burkina Faso; Togo
Additional data:
Upper elevation limit (metres):1600
Range Map:Click here to open the map viewer and explore range.

Population [top]


Chimpanzee population estimates are made using a standard index of abundance: night nest abundance and distribution, sometimes combined with predictive modelling. The total population estimate for P. t. verus is 18,000–65,000 (Sop et al. in prep.). Already P. t. verus is almost certainly extinct in Benin, Burkina-Faso and Togo (Ginn et al. 2013, Campbell and Houngbedji 2015). Its numbers are in the low hundreds in Ghana (Danquah et al. 2012), Guinea-Bissau (Carvalho et al. 2013) and Senegal (e.g., Pruetz and Bertolani 2009). Pan t. verus therefore persists mainly in Côte d’Ivoire (Campbell et al. 2008, Granier 2013), Guinea (e.g., Ham 1998, Kormos, Humle et al. 2003), Liberia (Tweh et al. 2015), Mali (Duvall et al. 2003), and Sierra Leone (Brncic et al. 2010). Côte d’Ivoire has seen a catastrophic decline of about 90% of its Chimpanzee population (Campbell et al. 2008).

Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:Unknown
Continuing decline in subpopulations:Yes
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:

Pan t. verus is found predominantly in dry and moist lowland tropical forests, and forest galleries extending into savannah woodlands. In West Africa, Chimpanzees also occur in fallow-agricultural matrices dominated by wild or feral oil palm (Leciak et al. 2005, Brncic et al. 2010, Sousa et al. 2011). Western Chimpanzees are omnivorous, and their diets vary greatly between populations and seasons. Fruit comprises about half the diet, but leaves, bark and stems are also important. Mammals or insects form a small but significant component of the diet of most populations. Western Chimpanzees form communities of ~12 to at least 84 individuals (Boesch and Boesch-Achermann 2001, Matsuzawa et al. 2011). Home range sizes of 15–65 km² have been estimated. Chimpanzees range further in savanna-dominated landscapes than in mixed forest (Pruetz and Bertolani 2009, Matsuzawa et al. 2011).

Generation Length (years):23
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade:

Chimpanzees are completely protected by national and international laws in all countries of their range, and it is, therefore, illegal to kill, capture or trade in live Chimpanzees or their body parts.

Threats [top]

Major Threat(s): The major threats to Pan troglodytes verus are:

1. Habitat loss and fragmentation, with varying impacts on populations and caused mainly by:

(a) Slash-and-burn agriculture: deforestation across West Africa has severely reduced Chimpanzee habitats. Rapidly growing human populations are expected to cause continued widespread conversion of forest and woodland to agricultural land.

(b) Commercial agriculture: in some African countries propitious to oil palm and other large-scale agricultural developments, such as rubber, eucalyptus and sugar cane, more than two-thirds of the land suitable for oil-palm development is unprotected Chimpanzee habitat (Wich et al. 2014). Liberia and Sierra Leone—strongholds for P. t. verus—are particularly vulnerable (ibid.). Changes caused by the rapid transformation of ape habitat can have profound impacts on Chimpanzee food availability, activity patterns, natural dispersal and ranging patterns, social systems, exposure to new pathogens and other risks linked to close proximity with people (Ancrenaz et al. 2015).

(c) Extractive industries (logging, mining, oil): increased accessibility to remote areas through road building and associated infrastructures, such as railways, poses risks to Chimpanzee populations through habitat degradation and fragmentation, increased illegal hunting, and logging in areas previously not seriously impacted by such anthropogenic pressures (Williamson et al. 2014). Logging generally, but not always, has a negative impact on Chimpanzee densities due to habitat alteration (principally removal of important food trees) and disturbance (Morgan et al. 2007).

Habitat loss and fragmentation is also associated with increasing reports of Chimpanzees foraging on crops across West Africa. Resource competition between people and Chimpanzees is expected to increase, posing serious risks of deliberate killing, retaliation or capture as a result of people’s negative perceptions and/or intolerance to crop offtake and Chimpanzee incursions into crop fields or plantations (Hockings and Humle 2009).

2. Poaching. Due to their low population densities and slow reproductive rates, hunting can lead to rapid local extirpation of Chimpanzee populations. The main reasons for illegal hunting are:

(a) Bushmeat: commercial hunting, often facilitated by logging activities, has caused declines in Chimpanzee populations in other regions (e.g., Wilkie and Carpenter 1999, Tutin et al. 2005), and in Côte d’Ivoire Chimpanzees constitute 1–3% of bushmeat sold in urban markets (Caspary et al. 2001). During a more recent one-month survey in Liberia, Greengrass (2015) recorded the carcasses of 74 Chimpanzees killed by professional hunters, as well as eight captured infants, at two camping sites at the periphery of Sapo National Park.

(b) Live trade: the capture of an infant Chimpanzee usually implies the death of its mother and often other members of the community (Carter 2003). Although the pet trade is illegal in all range countries that are signatories to CITES, it persists across the region (e.g., CITES Secretariat 2014).

(c) Traditional medicine: in some localities, Chimpanzees are killed for their body parts to satisfy for traditional beliefs (e.g., Gippoliti and Dell'Omo 1995).

(d) Crop protection: people kill Chimpanzees intentionally to protect their crops (Brncic et al. 2010). Chimpanzees may also be maimed or killed unintentionally when caught in snares set for other animals, such as baboons or cane rats (ibid.)

3. Disease. Infectious diseases are the main cause of death in Chimpanzees at Bossou (Humle 2011) and Taï (e.g., Köndgen et al. 2008). Because Chimpanzees and humans are so similar, Chimpanzees succumb to many diseases that also afflict humans (Leendertz et al. 2006). The frequency of encounters between Chimpanzees and humans and/or human waste is increasing as human populations expand and people encroach into Chimpanzee habitat, leading to higher risks of disease transmission between humans and Chimpanzees. If not properly managed, research and tourism also present a risk of disease transmission between humans and Chimpanzees (Gilardi et al. 2015). There is no evidence to date that the recent dramatic Ebola epidemic in West Africa affected Chimpanzees, although Ebola killed Chimpanzees in Côte d’Ivoire in the mid-1990s (Formenty 1999). The high potential risk that Ebola presents to great ape populations is exemplified by the repeated epidemics that have caused dramatic declines in Chimpanzee and gorilla populations in remote protected areas in Gabon and the Republic of Congo (e.g., Walsh et al. 2003).

Conservation Actions [top]

Conservation Actions: Pan troglodytes is listed on Appendix I of CITES and as Class A of the African Convention on the Conservation of Nature and Natural Resources. Chimpanzees are protected by national and international laws throughout their range, but enforcement is generally weak. Western Chimpanzees occur in numerous national parks; however, the majority (>70%) occur outside protected areas (IUCN SSC A.P.E.S. database 2016). National and international laws controlling hunting or capture of great apes exist in all habitat countries, but enforcement of protective legislation is almost non-existent.

In 2003, a Regional Action Plan for West African Chimpanzees generated numerous conservation actions (Kormos et al. 2003). A second, more succinct action plan was published in the same year (Kormos and Boesch 2003). These are available for download at:

See Conservation Actions Needed for additional actions proposed in light of emerging threats, which are especially relevant to the increasing threat posed by extraction and industrialised agricultural developments and heightened resource competition between people and Chimpanzees in the region.

Errata [top]

Errata reason: This is an errata version of the 2016 assessment to correct some minor typos and grammatical errors in the Threats section.

Citation: Humle, T., Boesch, C., Campbell, G., Junker, J., Koops, K., Kuehl, H. & Sop, T. 2016. Pan troglodytes ssp. verus (errata version published in 2016). The IUCN Red List of Threatened Species 2016: e.T15935A102327574. . Downloaded on 17 August 2018.
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