Owl-faced guenon (Cercopithecus hamlyni)

Also known as: Hamlyn’s guenon, Hamlyn’s monkey, owl-faced monkey
French: Cercopithèque D'Hamlyn
GenusCercopithecus (1)
SizeHead-body length: 56 cm (2)
Male weight: 5.5 kg (2)
Female weight: 3.4 kg (2)

Classified as Vulnerable (VU) on the IUCN Red List (1), and listed on Appendix II of CITES (3).

The owl-faced guenon is an unusual-looking monkey whose large, round head, triangular face and large eyes give it a somewhat owl-like appearance. The name ‘guenon’ is given to a group of monkeys with distinctive ‘moustaches’, light nose spots or striped sideburns (4). The owl-faced guenon has a silky, olive coat, a black face with a yellowish patch above the brow, and a thin, white stripe running down the nose. The long tail is ash-grey and ends in a black tassel, and the rear end and scrotum of the guenon are bright blue (2) (4). Two subspecies have been described in the past, Cercopithecus hamlyni hamlyni and Cercopithecus hamlyni kahuziensis (5), but the status of C. h. kahuziensis is now in doubt (1) (6), and, as such, it is not currently recognised as a distinct subspecies, pending further investigation (1).

The owl-faced guenon occurs in eastern Democratic Republic of the Congo, northwestern Rwanda, and Uganda (1) (2) (6).

The owl-faced guenon primarily inhabits dense montane rainforest, but can also occur in lowland forest (5).

The owl-faced guenon is thought to be largely terrestrial, spending most of its time on the ground (4) (6). It has two peaks of daily activity; one in the early morning, and then again in the late afternoon or evening (7). Living in small groups with a single male (2), the owl-faced guenon is apparently territorial, but avoids serious conflicts with neighbouring groups (7).

This omnivorous monkey feeds on fruit, insects and leaves (2). Its fairly large incisors are perfect for biting into fruit, and the flatter molars are suited to crushing and grinding hard seeds. It also possesses cheek pouches, the advantages of which are twofold: in areas where competition for fruit is intense, the monkey can grab as much food as possible before being supplanted by another hungry monkey, and at the same time, enzymes in the saliva help break down toxic compounds in unripe fruits and seeds stored in the pouches (8).

Guenons are vulnerable to both the bushmeat trade and human disruption of forests. Destruction of forest habitat throughout its range continues due to agricultural expansion and logging (7). Logging operations result in an increase in workers in the area, causing an increased demand for bushmeat, and logging roads make remote forests more accessible to hunters seeking meat to sell in local markets. In central and west Africa, a guenon carcass can fetch the equivalent of US $5 (8). Forests surrounding Mount Kahuzi are under increasing pressure from rapidly rising human populations. An influx of Rwandan refugees in 1994 and rebel soldiers from 1997 resulted in widespread forest clearance for agriculture and hunting (9). The year 2000 also saw a rush for the valuable industrial mineral coltan, which attracted more than 10,000 miners to the Kahuz-Biéga National Park in which Mount Kahuzi lies, and led to drastic deforestation and poaching (9).

The owl-faced guenon can be found within a small number of protected areas, such as the Okapi Faunal Reserve and the Kahuzi-Biéga National Park in the Democratic Republic of Congo (9) (10), but, as mentioned above, these generally offer only nominal protection. This species is likely to benefit from the increased protection and management of these areas, but at present, the situation in this volatile region is often too dangerous for action to be taken.

For further information on guenons see:

Authenticated (26/03/09) by Matthew Richardson, primatologist and author.

  1. IUCN Red List (September, 2013)