CALABAR ANGWANTIBO

Arctocebus calabarensis

Geographic Distribution and Habitat
The Calabar angwantibo is also known as the Calabar potto, the potto calabarensis, and the golden potto. They are not pottos, but are a unique, closely related species. The Calabar angwantibo belongs to the Arctocebus genus of the Lorisidae family. It is a lesser-known prosimian primate that shares many characteristics with African pottos and Asian lorises.

Calabar angwantibos have very localized distribution. They are only found in patches of lowland rainforests in western Cameroon and eastern Nigeria between the Sanaga and Niger rivers. There, they live in the dense forest undergrowth where lianas and vines thrive.

Calabar angwantibo range, IUCN 2008

Size, Weight, and Lifespan
Calabar angwantibos are small prosimian primates with a body measuring 9–11 inches (23–30 cm) and a tail that is barely 3 inches (8 cm) long. Both male and female adults are of comparable size and only weigh between 9 and 16 ounces (250–465 grams).

They can live up to 13 years in captivity. Their lifespan in the wild is not documented.

Appearance
Calabar angwantibos have reddish-brown fur on the back and light gray fur on the belly. Their nose is accentuated by a white line that extends from the forehead to the tip of the snout. Their ears are triangular and quite large compared to the head. Their brown-orange round eyes are delineated by a circle of black fur. The eyes contain a nictitating membrane that extends over the entire eye, like a third eyelid. This transparent membrane protects and hydrates the eye while allowing the animal see through it.

Calabar angwantibos’ hands and feet each have five digits and are designed to allow a solid secure grip on branches as they climb and hang. The second digit of the hand is very short and the big toe is widely separated from the rest of the toes to further facilitate their unique locomotion. They keep their dense pelage clean by using a toilet claw that resides on the second toe of each foot.

Photo credit: ©Averee Luhrs/iNaturalist/Creative Commons

Diet
Calabar angwantibos consume insects—mostly caterpillars—which are rich in protein, fat, and iron. Since the caterpillars are covered in venomous hair, angwantibos do not have much competition for this particular food source. About 85% of their nutritional needs are met from this one staple. Fruits and gums supplement their diet.

The angwantibos use a unique technique for capturing caterpillars—holding their heads close to the branch they stand on, they use their long noses to detect their prey and grasp it with their hands. With the dexterity that few animals (other than primates) possess, they massage the caterpillar, extending it until the toxic hair and spines are removed. Then, they squeeze and devour the body.

What Does It Mean?

Allogrooming:
Social grooming within a species.

Desertificatiion:
The process by which fertile land becomes desert, typically as a result of drought, deforestation, or inappropriate agriculture.

​Lorisidae:
A family of slim arboreal strepsirrhine primates (i.e. primates with a wet nose) found in tropical Africa and Southeast Asia. 

Nictitating membrane:
A whitish or translucent membrane that forms an inner eyelid in birds, reptiles, and some mammals. It can be drawn across the eye to protect it from dust and keep it moist.

Parking:
Refers to mothers leaving their young alone in the nest at night.

Prosimians:
The most primitive of the primates. “Prosimian” means pre-monkey. The living (extant) prosimians are in the suborder Prosimii, ​which includes four families of lemurs, the bush babies (galagos), lorises and pottos, angwantibos, and the tarsiers.

Viverrids:
Small to medium-sized carnivorous mammals that include 33 species. including Africa civets and genets.

Visit the Glossary for more definitions

Behavior and Lifestyle
Calabar angwantibos are nocturnal and arboreal. They spend most of their time (95%) foraging alone in the lower canopy in trees with small branches, 15–50 feet (5–15 m) above ground.  

Because they move slowly in dense foliage and their fur is not bright, they are not easily detected by predators. Moving slowly also works to their advantage when hunting; they can surprise unsuspecting prey.  

It is not unusual for angwantibos to remain still while hanging from a branch. They can easily do so because the muscles in their limbs can remain contracted for a very long time without any interruption to normal blood flow. Their muscles, therefore, continue to receive oxygen and don’t get tired or numb.

Daily Life and Group Dynamics 
An angwantibo male’s territory usually overlaps the territories of several females. Therefore, although they forage solitarily, males and females have the opportunity to interact when they meet within their respective borders. They mark those territorial boundaries by urinating and/or rubbing their scent glands on branches.

When faced with a predator, angwantibos are said to tuck their head under their body and extend out their limbs, making themselves as stiff as possible. If the predator moves in, they bite at it while keeping their head under their armpit.

Fun Facts

The Calabar angwantibo is named after the city of Calabar in Southeast Nigeria. The city was built on a hill that overlooks the Calabar River.

Communication
Smell is the primary means of communicate for angwantibos. Urine and gland secretions contain a host of information a Calabar angwantibo may need to know about another individual, such as territorial boundaries, gender, age, and location. 

It is possible that they do not vocalize much to avoid attracting attention from predators. However, mothers and offspring exchange high-pitch clicking calls to stay connected while the mother is out foraging. 

Calabar angwantibos have also been heard groaning when threatened.

Reproduction and Family
Males find receptive females through scent. When they meet, they initiate allogrooming sessions and a ritual called “passing over” during which the male climbs over the female while rubbing his scrotum on her fur.

After a gestation period of approximately 135 days, the mother stands on a branch and gives birth to her offspring, weighing about 0.9 ounces (26 g), who immediately attaches to her belly. After a few days, when the infant is strong enough, he or she climbs on the mother’s back. The mother nurses the infant and “parks” it when she goes out to forage.

At about 3 months (115 days), when the baby weight reaches almost 6 ounces, the youngster is weaned, but remains with its mother until it reaches maturity at approximately 9 months of age (270 days for males; 279 days for females).

Since there is no specific mating season, mothers can give birth again 4.5 months later.

Few photos of Calabar angwantibos are available. This antique rendering is by John Wolf, Zoological Society of London, 1864

Ecological Role
Since angwantibos primarily consume caterpillars, they probably contribute to insect population control.

Conservation Status and Threats
The International Union for Conservation of Nature lists the Calabar angwantibo as Near Threatened (IUCN, 2016), appearing on the IUCN’s Red List of Threatened Species. In the last 15 years, the population is estimated to have declined by approximately 20%.

Calabar angwantibos’ natural predators include viverrids, snakes, and large birds of prey, but the greatest threat to their survival is habitat loss. Rapid deforestation is pushing these primates closer to human agricultural areas than ever before and even if, until now, the species has been able to survive in degraded habitat, there is no telling how much longer it can go on.  

Nigeria lost 59% of its forest cover between 1990 and 2015, compared to 22% for Cameroon. With 200 million people, Nigeria is the most populated country in Africa. Feeding an extremely poor human population is the main priority for the country. Many forested areas (such as the Cross River National Park) have been converted to monocultures for agro-business (mostly bananas, coconut, and oil palm). The forest is also threatened by illegal logging as well as slash and burn agriculture for family farming. Unsustainable agricultural practices and overexploitation of natural resources are causing desertification and water and air pollution, not to mention severe habitat degradation. Under such circumstances, not only are animal species like the Calabar angwantibo impacted, but so are plants—this is how several rainforest native trees, like zebrawood and ebony, have disappeared.

There is no evidence that Calabar angwantibos are captured for the pet trade. However, illegal poaching is another real threat. These animals are often killed by hunters—not necessarily intentionally, but because they happen to get caught in snares and traps meant for larger animals. Calabar angwantibos are too small to be sold on markets for a hefty sum of money, but they provide an easy meal to hunters while they are in the forest—even if their meat is reportedly very tough. Consuming their flesh is not taboo and some local beliefs support the practice, by encouraging pregnant women, for instance, to take a bite to ensure their newborn will have sturdy legs. Their body parts can also be used for other folk medicine or witchcraft; smearing their grinded bones over one’s body is purported to make one stronger. 

Conservation Efforts
Cameroon is Africa’s 5th richest country in biodiversity, behind the DRC, Madagascar, Tanzania, and South Africa. In 2020, the government launched the Green Campus project, planting trees in all public and private schools to educate youth about the importance of reforestation. This is not new. Already, in 2006, the Cameroon ministry of forest and fauna, with LAGA—the first wildlife law enforcement nonprofit—wrote decree 0648/MINFOF to ensure the protection of endangered species. The Calabar angwantibo is included in the class A of mammals protected under the law and, as such, should not, theoretically, be captured or killed under any circumstances. Enforcing this law is one of biggest conservation challenges in the country.

In Nigeria, protected areas are few and conservation laws are not easily implemented, but ecotourism may be one way to bring in revenue to the Cross River State, where mountain gorillas and Calabar angwantibos live. Scientists and NGOs recommend stronger involvement from the Nigerian government, the implementation of more educational programs and degrees that would open doors to conservation careers for locals. They also recommend more projects encouraging locals to participate in wildlife conservation and natural resources management.  

The one message from conservation experts we ought to remember is that humans, other animal species, and plants are interconnected and cannot live without one another.

​References:

  • IUCN Red List
  • Behaviour of Pottos and Angwantibos – Magdalena S. Svensson and Averee M Luhrs
  • Wikipedia
  • Nutritional contributions of insects to primate diets: Implications for primate evolution – Jessica Rothman, David Raubenheimer, Margaret A.H. Bryer, Maresssa Takahashi, Christopher C. Gilbert
  • www.guwsmedical.info/mammals-3/calabar-angwantibo
  • www.genomics.senescence.info/species/entry.php?species=Arctocebus_calabarensis
  • Threats from trading and hunting of pottos and angwantibos in Africa resemble those faced by slow lorises in Asia – Magdalena S Svensson, Sagan C Friant
  • www.afw.org 
  • Primates of the World – Jean-Jacques Petter and François Desbordes
  • La Législation Faunique Camerounaise comme un outil de protection des espèces animales menacées d’extinction au Cameroun – Ministère des forêts et de la faune (MINFOF) – direction de la faune et des aires protégées – Assisté pare Last Great Ape Organization (LAGA), financé par Arcus Foundation et Born Free Foundation – Robinson Djeukam (2012)
  • www.Afrik21.africa – Cameroon: Africa’s 4th biodiversity reserve calls for eco-citizenship – Boris Ngounou
  • Nigeria – Biodiversity and Tropical Forests 118/119 Assessment – Beth Hahn USDA Forest Service (2013)
  • A review of the biodiversity conservation status of Nigeria – Odoligie Imarhiagbe, Wisdom Oghenevwogaga Egboduku, Beluchkwu Joseph Nwankwo
  • www.factinstitute.com

Written by Sylvie Abrams, August 2021