Preuss’s guenon  (Cercopithecus preussi)

Classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix II of CITES (3). Subspecies: the Cameroon Preuss’ monkey (C. p. preussi) and the Bioko Preuss’ guenon (C. p. insularis) are listed as Endangered (EN) on the IUCN Red List (1).

The most distinguishing feature of this monkey is the white patch of fur that forms a fluffy ‘bib’ on its face (4). Preuss’s guenon has a long, curling tail and grey or black coat, with a brown saddle-shaped area of fur on its back (4) (5). Typically, male guenons are larger than females (6).

Preuss’s guenon is found in western Cameroon, eastern Nigeria and on Bioko Island (Equatorial Guinea). Two subspecies are recognised: Cercopithecus preussi preussi occurs on the mainland while Cercopithecus preussi insularis is restricted to Bioko Island (1).

Preuss’s guenon occurs primarily above 800 metres, where it is found in montane and submontane forest, although it can also be found at lower altitudes in some areas, such as Bioko Island (1). 

The social group of Preuss’s guenon consists of two to twelve individuals, usually comprising just one adult male, while the rest are females and their young (1); only rarely is there more than one male in a group. Preuss’s guenon is a polygynous species, meaning that each male mates with more than one female (7). It is the female that initiates mating, seeking the attention of a male and letting the male know she is ready to mate. A female gives birth to only a single young at a time (7).

Living in social groups dictates a need for communication, which Preuss’s guenon does using both visual and vocal signals, such as the low-frequency, territorial ‘boom call’ of the male (7). The visual displays are typically threatening, and include staring and opening the mouth with the teeth covered, head-bobbing accompanied by staring, and yawning whilst showing the teeth (7).

The diet of this primate consists primarily of fruit, mature tree leaves and, preferentially, leaf shoots (8), but it is also known to eat seeds and flowers (1).  

Over the past 27 years, populations of Preuss’s guenon have decreased by an incredible 50 percent (1), due to a combination of habitat loss and hunting. As a result of farming, fire, and the collection of wood for fuel, little of Cameroon’s montane forest remains. Preuss’s guenon is particularly vulnerable to hunting due to its fairly large size and its semi-terrestrial habits; spending time on land increases its risk of being killed. Hunting of this species is a particular problem on the island of Bioko (1).

A significant hindrance to the conservation of this species is that no montane forest in the Cameroon highlands is currently protected; this situation needs to urgently change, as it is the most critical remaining habitat for Preuss’s guenon. However, there are several national parks elsewhere in this monkeys’ range including Banyang Hbo Forest in Cameroon, Cross River National Park in Nigeria, and Pico Basil National Park on Bioko Island (1). This species is also listed in the African Convention as Class B, which means it is protected, but may be hunted, captured, collected or killed if special authorisation is given (9).

View information on this species at the UNEP World Conservation Monitoring Centre.

To learn about conservation efforts on Bioko Island see:

• Bioko Biodiversity Protection Program:
  http://www.bioko.org

 To find out about the conservation of primates around the world see:

• IUCN/SSC Primate Specialist Group:
  http://www.primate-sg.org
• Centre for Education, Research and Conservation of Primates and Nature:
  http://www.cercopan.org