Piliocolobus pennantii

Geographic Distribution and Habitat

Red colobus monkeys have been called the most threatened taxonomic group of African primates. The Pennant’s red colobus is, sadly, no exception. It is Critically Endangered and regularly featured on the list of the 25 most endangered primate species in the world. These monkeys are endemic to Equatorial Guinea and are found only on the island on Bioko. The remaining range of the entire species is limited to just 40,000 acres (16,000 ha) in Gran Caldera Scientific Reserve at elevations from 0 to about 4,000 feet (0–1200 m). This reserve is made of lowland and mid-montane tropical moist forest, and marsh forest, sometimes known as “monsoon” forests due to the large amount of rainfall they receive. The Pennant’s red colobus likely lived in other locations across Bioko until fairly recently, but the combined threats of habitat loss and hunting have decreased their known range to the very southwest of Bioko.


The Pennant’s red colobus species has a complicated taxonomic history, until recently being classified as a subspecies, along with the Niger Delta red colobus and western red colobus. However, scientific analyses has recently identified that each of these three are indeed stand-alone species.

Pennants red colobus range, IUCN 2018

Size, Weight, and Lifespan

Adult male and female Pennant’s red colobuses are of a similar size, with head and body length reaching an average of 18.5–23 in (47–58 cm) for females and 18.5–22 in (47–55 cm) for males. Tail length averages 25 in (64 cm) in females and 23 in (59 cm) in males. Adults weigh approximately 20–24 lbs (9–11 kg).

Like many other monkeys, they do show sexual dimorphism in some traits that are likely controlled by sexual selection, such as canine length. Female upper canines measure only around 0.28 in (0.7 cm), compared to an impressive 0.67 in (1.7 cm) in males.

Although the lifespan of this species is not well known, based on closely related species they probably live around 20 years.


The Pennant’s red colobus has a gray face, the lower half of which is framed by distinctive white hair forming elaborate cheek tufts. The tops of their heads, as well as their backs and hands and feet, are all covered with black hair, which changes to varying shades of orangey-red on their sides, outer limbs, and tails. Their belly, chest, and inner limbs are all cream-colored. They are relatively large-bodied primates and have long fingers that are perfectly evolved to help them move through the trees, while their long, non-prehensile tail helps them maintain their balance.

Photo courtesy of ©Pierre Munch

Like other species of red colobus, the Pennant’s red colobus is primarily a leaf eater, preferring young, immature leaves from a variety of trees. Its morphology, from its stomach to its teeth, is well adapted to being a folivore and obtaining the maximum amount of nutrients from leaves, while sometimes supplementing these with fruits and seeds.

Behavior and Lifestyle

These monkeys are diurnal and arboreal, sleeping high in the trees at night, moving through the trees during the day. They likely divide their day between traveling, foraging, taking part in social activities such as grooming, and resting in the trees.

Fun Facts

The Pennant’s red colobus is found only on the island of Bioko in Equatoral Guinea.

They have lost 80% of their population in the past 30 years.

They are highly threatened by the bushmeat trade and are an easy target for hunters.

Daily Life and Group Dynamics 

Pennant’s red colobus monkeys appear to live in smaller groups than other red colobuses; although initial estimates suggested group size may range from 5 to 30 individuals, only 20 individuals have been observed in the same group. Indeed, average group size seems to lie between 2 and 3 monkeys, likely comprising a male, a female, and their offspring. Within the larger groups, there may be multiple adult males and adult females. In closely related species, both sexes are known to disperse and join or found new groups.


Given that these monkeys spend much of their time in the trees, it is likely that vocal communication plays a primary role in when they communicate with each other.

Red colobuses are known to have a complex vocal repertoire, and likely produce at least 25 different calls. Adult males tend to vocalize more than females or juveniles, perhaps to signal to other males, although females and juveniles also emit a range of calls. These monkeys call in a number of different situations, including when a predator is sighted, during inter-group interactions, and when in distress.

It is likely that, in addition to vocalizations, these monkeys also communicate via gestures and facial expressions, although these forms of communication are only useful when the monkeys are close together.

Reproduction and Family

While little is known of the reproductive life of the Pennant’s red colobus, it is likely similar to other species of red colobus monkeys, where females give birth to one infant every two years after a gestational period of between 4 and 6 months. The females will likely carry their infant on their bellies for at least the first few months of life before they are old enough to begin moving and traveling independently.

Photo courtesy of ©Pierre Munch
Ecological Role

As folivores, these monkeys likely play a role in the forest ecosystem by pruning leaves from a variety of trees. When they eat fruits, they may act as seed dispersers, moving seeds away from their parent tree to other parts of the forest.

Conservation Status and Threats

The International Union for Conservation of Nature lists the Pennant’s red colobus as classified as Critically Endangered (IUCN, 2016), appearing on the IUCN’s Red List of Threatened Species. There are probably fewer than 1,200 animals remaining and it is estimated that their population has declined by 80% over the past 30 years.

The greatest threat to this species has been from hunting for the bushmeat trade. Unfortunately, Pennant’s red colobus monkeys are highly preferred by bushmeat hunters and their large size makes them easy targets for hunters with guns. While hunting these monkeys is officially banned, there is little on-the-ground protection for them, and hunting continues to deplete their numbers. Continuing demand for their meat, combined with human-caused disturbance in their remaining habitat means that, without intervention, they will likely become extinct in the near future.

Conservation Efforts

Pennant’s red colobus monkeys have considerable official protection, such as being listed on Appendix II of the Convention on International Trade in Endangered Species (CITES) and on Class B of the African Convention on the Conservation of Nature and Natural Resources. They are also included in the Red Colobus Conservation Action Plan (ReCAP). The small area where they still occur is a protected area and the hunting, sale, and consumption of all primates was banned in Equatorial Guinea in 2007. However, this hunting ban is not effectively enforced and there in no management plan of the Gran Caldera Scientific Reserve.

Some conservation projects are being implemented in the Gran Caldera Scientific Reserve and include a focus on primate monitoring, education and outreach, training of eco-guards, and the development of alternative livelihoods that deter bushmeat hunting. In order to conserve this species, scientists have suggested that conservation efforts should include the development and implementation of a management plan for the Gran Caldera Scientific Reserve, as well as strengthening the legal, and practical, protections for these monkeys with a focus on halting the bushmeat trade. 

  • Cronin, D.T. 2019. Piliocolobus pennantiiThe IUCN Red List of Threatened Species 2019: e.T41025A92653653. 
  •  Cronin, D. T., Riaco, C., Linder, J. M., Bergl, R. A., Gonder, M. K., O’Connor, M. P., & Hearn, G. W. (2016). Impact of gun-hunting on monkey species and implications for primate conservation on Bioko Island, Equatorial Guinea. Biological Conservation197, 180-189.
  • Cronin, D.T., Woloszynek, S., Morra, W.A., Honarvar, S., Linder, J.M., Gonder, M.K., O’Connor, M.P. & Hearn, G.W. 2015. Long-term urban market dynamics reveal increased bushmeat carcass volume despite economic growth and proactive environmental legislation on Bioko Island, Equatorial Guinea. PLoS One : e0134464.
  • Struhsaker, T. T. (2010). The red colobus monkeys: variation in demography, behavior, and ecology of endangered species. Oxford University Press.
  • Struhsaker, T. T. (2010). Variation in adult sex ratios of red colobus monkey social groups : implications for interspecific comparisons. In (Ed) P. Kappeler, Primate Males: Causes and Consequences of Variation in Group Composition. Cambridge University Press.
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Written by Jennifer Botting, PhD, March 2022