GOLDEN ANGWANTIBO

Arctocebus aureus

Geographic Distribution and Habitat
The golden angwantibo (Arctocebus aureus) is endemic to Africa, residing in the continent’s western-central region in an area that comprises the Congo Basin, known as “the green heart of Africa.” Geographic distribution for this enigmatic primate is thought to extend from the Sanaga River in Cameroon, through Equatorial Guinea, Gabon, and Congo, to the Congo and Ubangi rivers in the Central African Republic. Populations are highly localized and occur sporadically throughout a range where precise boundaries remain unknown.

Moist evergreen, lowland rainforests, along with tall deciduous forests with high tree-fall areas, provide golden angwantibos with their preferred habitat. They dwell within dense, leafy vine tangles of the understory in primary and secondary forests at low to medium elevations, typically less than 16.4 ft (5 m) above the forest floor. These primates are also unwelcome visitors to plantations and farmlands.

TAXONOMY IN TRANSITION

​Prior to attaining full species status, the golden angwantibo was considered a subspecies of the Calabar angwantibo (A. calabarensis), also known as the Calabar potto. The two species are sometimes referred to together as golden pottos; however, neither of these two primates is a true potto. Rather, they are both prosimian primates belonging to the primitive suborder Strepsirrhini (characterized, in part, by their moist or “wet” noses) within the family Lorisidae, whose other family members include pottos along with lorises. A point of distinction: the golden angwantibo and the Calabar angwantibo are the only two species who occupy the genus Arctocebus.

Golden angwantibo range, IUCN 2008

Size, Weight, and Lifespan
Golden angwantibos are tiny primates, similar in size to their Calabar “cousins.” Adults weigh a mere 9.4–16.4 oz (266–465 g) and grow only to 8.7–11.9 in (22–30 cm) in height. A vestigial stub of a tail fails to contribute to their overall body length. Sexual dimorphism is unremarkable in these prosimians.

Lifespan in the wild has not been reported. However, life expectancy for Calabar angwantibos is reported as 12 to 15 years.

Appearance
Did this curious-looking little prosimian swallow a bowling ball? No. But its portly physique suggests he enjoys the buffet table. Or maybe it’s the golden angwantibo’s hunched posture that contributes to this effect.


The dense, woolly fur coat that cloaks this primate’s back, shoulders, and slender limbs is reddish-gold in color. Frosted tips make one wonder whether the golden angwantibo has visited a rainforest hair salon. In actuality, these are lighter-colored “guard hairs” that protect the pelage from abrasion and moisture. Cream-colored fur covers the prosimian’s underside.

Large, brown eyes and a long, pointy nose dominate the face. Darker fur surrounds the eyes and a white strip of fur follows the length of the nose. Small, scalloped, naked ears jut out from either side of the head.

Five digits on hands and feet provide dexterity. Index fingers are shorter than others, and a specialized claw (known as a “toilet claw”) on the second digit of each foot (next to the big toe) assists angwantibos in grooming their dense fur coat.

A physical characteristic that distinguishes the golden angwantibo from its Calabar angwantibo cousin is the lack of a nictitating membrane, colloquially referred to as a “third eyelid.” (People who share their home with a feline may have noticed the occasional appearance of this so-called third eyelid, particularly when kitty is not feeling well but occasionally when kitty is just very sleepy.) This whitish membrane serves as an inner eyelid that helps keep the eye moist and protects it from dust. Most of the time, it retracts into the inner corner of the eye and is not visible. But, if need be, an animal equipped with a nictitating membrane can draw it across the eye for protection. Golden angwantibos, lacking this adaptation that Mother Nature saw fit to give to their Calabar cousins, cannot do this. Neither can we humans.

Photo credit: © Averee Luhrs/iNaturalist/Creative Commons

Diet
Golden angwantibos are primarily insectivores. Caterpillars—including the hairy, foul-tasting toxic species typically avoided by most other insectivores—are golden angwantibos’ food of choice. The wriggly creatures provide the prosimians with a good source of protein, fat, and iron. Golden angwantibos also eat other insects along with a small amount of fruits, particularly fruits that have fallen to the ground.

Behavior and Lifestyle
These solitary creatures are nocturnal, active during nighttime hours. Excellent night vision—thanks to an adaptation known as the tapetum lucidum, a thin membrane situated behind the eye’s retina that reflects light, colloquially referred to as “eye shine”—allows these prosimians to easily navigate in the darkness. (You might share your home with another creature who possesses this adaptation. That “glow” you see in your cat’s eyes as she walks stealthily through your dark backyard or living room? Eye shine. Cats, like prosimians, are endowed with night vision that is superior to that of us humans.)

Mostly arboreal, golden angwantibos spend the bulk of their time in trees. The dense underbrush and lower layers of the forest provide them with a level of safety, particularly during daylight hours while they curl up to sleep, hidden within tangles of liana vines from predators. (Mothers sleep with their infants; otherwise, golden angwantibos sleep solo.) Rarely do they climb higher than 49 ft (15 m) and are most often found perching on small branches no more than 16.4 ft (5 m) from the forest floor. Their tree height preference is strategic: at lower levels of the forest, they encounter less meal competition from birds (who are also insectivorous), and they find more insects to eat. Lower levels are also better shielded from nature’s elements. Their choice of branches to travel upon is about sensibility and physical capability. Golden angwantibos’ narrow hands and feet simply cannot grip large vertical branches. So, while traveling, these prosimians choose thin branches, less than 2.4 in (6 cm) in diameter, as they advance through dense and continuous vegetative walkways quadrupedally, carefully placing one hand over the other. Characteristic of primates within the Lorisidae family, golden angwantibos are languid in their movements. They are not leapers.

Foraging behavior is similar to that of their Calabar cousins. With their long, narrow muzzles pointed downward, led by a strong sense of smell, these prosimians are quiet and stealthy when hunting insect prey—but react with incredible swiftness and dexterity when reaching out with their strong hands to capture unaware creatures.

Prior to devouring poisonous caterpillars, angwantibos employ a curious technique. They “massage” the crawly insect’s spine, thereby discarding toxic hair follicles. Researchers have observed this behavior in young angwantibos as well. Because these youngsters are not yet able to capture insect prey on their own, researchers posit that this prey-massage behavior may be innate in these primates.

For a more varied insect selection, or to choose a piece of fallen fruit, golden angwantibos frequently descend to the ground to forage.

Their keen sense of smell also helps angwantibos detect predators—giving them a chance to camouflage themselves in their leafy environment, whereby remaining completely still, they can escape detection. (The practice of camouflage, scientifically known as “cryptic coloration,” is a defense mechanism that animals in the wild use to disguise their appearance by blending in with their surroundings for the purpose of avoiding predators—but camouflage is also used by some animals to sneak up on prey.) To protect themselves from a predator, angwantibos assume a defensive posture: nose down, limbs rigid and extended, head tucked under body. Should a predator approach, an angwantibo raises its hindquarters and, with its head tucked securely under its armpit, issues rapid bites to the predator.

Predators of angwantibos are thought to include viverrids (small- to medium-sized carnivorous mammals, including the weasel-like civet and the cat-like genet), snakes, large birds of prey—and their greatest predator: humans.

What Does It Mean?

Allogrooming:
Social grooming within a species.

Anthropogenic:
Environmental disturbance or environmental pollution originating in human activity.

Conspecific:
An animal of the same species.

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

Lothario:
A man who behaves selfishly and irresponsibly in his sexual relationships with women.
A seducer, debaucher, Casanova.

Pelage:
The fur, hair, or wool of a mammal.

Pheromone:
A chemical that an animal produces that changes the behavior of another animal of the same species.

Primary forest:
Also termed old-growth forest, virgin forest, or primeval forest—a forest that has attained great age without significant disturbance and thereby exhibits unique ecological features and might be classified as a climax community, an ecological community in which populations of plants or animals remain stable and exist in balance with each other and their environment.

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.

Quadrupedally:
Using four limbs to move about. This word comes from the Latin meaning “four feet.”

Secondary forest:
A forest that has regrown after a major disturbance, such as fire or timber harvest, but has not yet reached the mature state of primary forest.

Sexual dimorphism:
Distinct difference in size or appearance between the sexes of an animal in addition to difference between the reproductive organs themselves.

Species:
A group of living organisms (animals) consisting of similar individuals capable of exchanging genes or interbreeding. The species is the principal natural taxonomic unit, ranking below a genus.

Strepsirrhine or strepsirhine: 
Relating to the primate suborder Strepsirrhini, consisting of lemurs, lorises, and bush babies, who characteristically have moist areas around their nostrils.

​Subspecies:
A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

Sympatric: 
Occurring or living in the same area; overlapping in distribution.  

Visit the Glossary for more definitions

Daily Life and Group Dynamics 
The social lives of golden angwantibos are largely a mystery, much like their nocturnal lifestyle is shrouded in darkness, making field observations challenging for researchers. Unlike their Calabar cousins, whom researchers have successfully captured and observed in an outdoor caged setting, golden angwantibos have, thus far, evaded capture.

Primates of the Lorisidae family are believed to be loners. However, some researchers would like to dispel the notion of the exclusively solitary Lorisidae primate. They suggest that certain species of these nocturnal creatures choose to live in small family groups and engage in multiple displays of social behavior, apart from breeding. These activities include foraging and feeding.

Further conclusions are drawn from studying patterns of overlapping home ranges and through studies of communication between these conspecific primates.

But from what little is known about golden angwantibos, it appears that these lorisids are, in fact, true loners. The exceptions are mothers with their dependent offspring and, of course, when males and females come together to breed.

The Congo Basin is rich with sympatric species. Chimpanzees, mandrills, red and green monkeys, giant hawks, and eagles are a few of the species who live in Cameroon. Gorillas, leopards, hippopotamuses, forest elephants, bush elephants, and pythons live throughout Equatorial Guinea. Gabon’s wildlife includes forest elephants, bonobos, and giraffes. The Central African Republic is home to crocodiles, semiaquatic tortoises, and water snakes swim in the rivers of the Congo Basin.

Fun Facts

A subplot of British naturalist/writer-turned-zookeeper Gerald Durrell’s first book, The Overloaded Ark (1953), centers on his attempts to capture an angwantibo for zoological study. Thankfully, Durrell was unsuccessful, so angwantibos were not among the African animals he kidnapped and sold to zoos in England.

Bärenmaki, meaning “bear lemur,” is the German name for the golden angwantibo—due to the prosimian’s bear-like appearance. We don’t see the resemblance, though.

Communication
These are relatively silent primates. Angwantibos’ limited vocalizations (observed in captive Calabars) include a hissing call, emitted when distressed; a groan-like call, emitted when threatened; and a clicking call, shared between mothers and their infants. Researchers have posited that angwantibos may be communicating with one another through ultrasonic vocalizations. Further investigation is necessary.

Like pottos, angwantibos rely heavily on olfactory communication. To mark their territory, they urinate on tree branches, leaving “urine trails” along their travel paths. Other messages are conveyed through secretions released from specialized scent glands. Leaving sensory cues allows solitary golden angwantibos to communicate with one another without having to physically interact.

Angwantibos’ acute sense of smell is thanks to an adaption in the roof of the mouth, colloquially known as “Jacobson’s organ” and scientifically known as the vomeronasal organ. This organ contains a patch of sensory cells that detect moisture-borne scent particles. We humans are equipped with this organ, too. Whether or not this organ serves us is the topic of much scientific speculation. But you know what other animal has this organ and knows how to use it? Cats. (Of course.) And their organ contains far more scent receptors than ours. Perhaps you’ve seen a cat with her mouth slightly open, her upper lip curled as if she’s taking in a scent. That’s just what she’s doing. So if you’re trying to come up with an interesting name for a newly adopted kitty, consider “Angwantibo.” Spark conversation in primate conservation!

Reproduction and Family
The reproductive behavior of golden angwantibos is similar to that of their Calabar angwantibo cousins. Age of sexual maturity is between 9 and 10 months (no distinction is given between males and females). Males are opportunists and will mate with any female whose overlapping territory puts her on a male’s turf. Foreplay includes heavy petting sessions (or, rather, “allogrooming”) and a male maneuver referred to as “passing-over behavior.” In this Lothario maneuver, a male clambers over a female while rubbing his scrotum against her body, saturating her fur with pheromone secretions from his scrotal gland, thereby “claiming” her. Copulation occurs on a branch, as do births.

After a gestation period of 131–136 days, a single infant is born, weighing in at just 0.85–1.1 oz (24–30 g). Newborns cling to their mother’s furry stomach; as they become a bit older, they cling to her back. A mother may “park” her days-old infant on a tree branch as she goes off foraging, returning for her baby at dawn.

Mothers nurse their babies for 100–130 days, at which time young angwantibos are considered weaned. The species has no specific mating or birth season, and breeding often resumes immediately following births. Females typically give birth to one infant twice each year.

Photo credit: ©Rod Cassidy/iNaturalist/Creative Commons

Ecological Role
​With their enormous propensity for consuming insects, golden angwantibos can be thought of as Nature’s pest control primates. Seeds from the small amount of fruits they consume end up back in the soil (via the angwantibo’s feces) and might help to plant a tree or two.

Conservation Status and Threats
Because of the species’ relatively widespread distribution, the golden angwantibo is classified as Least Concern by the International Union for Conservation of Nature (IUCN, 2016), appearing on the IUCN Red List of Threatened Species. (Its Calabar cousin is classified as Near Threatened.) But this lesser threat classification does not mean there is no cause for alarm. These prosimians are routinely killed, their dismembered body parts used to make traditional medicines and their flesh cut into slabs and sold as bushmeat in local markets. Not too long ago, human predation was a lesser threat to golden angwantibos. But as other larger wildlife species have been hunted to the point of scarcity, tiny golden angwantibos have become a choice prey of human hunters. Wildlife laws intended to protect the species are routinely flouted.

The biggest threat against golden angwantibos, however, is loss of habitat. Throughout the Congo Basin—one of the earth’s most important wilderness areas (and second largest river basin, after the Amazon)—pristine rainforests are disappearing through anthropogenic activities. With the loss of habitat comes the loss of wildlife.

Golden angwantibos are not able to easily establish themselves in a new area; thus, habitat loss and fragmentation pose a serious threat to their long-term survival. The looming climate crisis makes the situation even more grave.

In Gabon, where golden angwantibos are considered rare, unsustainable and illegal logging is the obvious culprit. Population densities of only 2 individuals per square kilometer were found in dense primary forest, and 7 individuals per square kilometer were found in thickets of secondary forest (as reported by the IUCN, 2016).

But it is small-scale tree clearing, conducted by local people using rudimentary axes, that is responsible for more than 80 percent of the region’s total forest loss. Poverty, stemming from political instability and conflict in the region, has driven locals to clear tracts of forest for subsistence farming. These novel farmers are without other livelihood options and need to feed their families. Unfortunately, their farming practices—besides vanquishing swaths of pristine forest—deplete the land of nutrients. In what is described as “shifting cultivation,” farmers abandon tracts of land as the soil becomes infertile and take down more trees to create new tracts of farmland—perpetuating a detrimental cycle.

A study conducted by researchers from the University of Maryland (UMD) in the U.S. revealed (through satellite images) that between 2000 and 2014, about 63,707 sq mi (165,000 sq km) of Congo Basin Forest was lost to shifting cultivation. These researchers warn that if these current practices continue, by the year 2100 no primary Congo rainforests will remain.

Conservation Efforts
Golden angwantibos are listed as Class B under the African Convention and in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.

Wildlife biologists presume that populations of golden angwantibos occur within the national parks throughout the species’ range. But they can’t say for certain, as few field studies have been conducted on this cryptic species. As such, biologists call for increased research through long-term observation within golden angwantibo habitat—along with the use of radio telemetry—to monitor population trends, help preserve habitat, identify possible risks, and know more about this prosimian’s social behavior.

Conservation groups working to protect golden angwantibos and the Congo Basin include the World Wildlife Fund (WWF) and African Wildlife Foundation (AWF), working with rangers and officials from the region’s national parks and reserves. As an example, in Cameroon AWF is training rangers to thwart poaching activity and providing them with support to effectively enforce wildlife protection laws. AWF is also working with local communities to create sustainable income-generating livelihoods by crafting non-timber forest products into goods for sale. For example, bush mango and the njansang plant are used to produce oils and butters. Additionally, AWF is engaging citizens in wildlife monitoring and conservation plans.

In 2007, the country of Gabon created a national park agency, Agence Nationale des Parcs Nationaux (ANPN). APN’s overarching goal is to conserve Gabon’s wildlife heritage by enhancing its capacity to effectively manage protected areas and provide leadership for conservation in Central Africa.

How You Can Help:
For simple actions you can take to help ensure the golden angwantibo’s survival, and that of other endangered wildlife species and their habitat, visit: What You Can Do for Animals and the Environment.

​References:

  • Erickson-Davis, Morgan. “Congo Basin Rainforest May Be Gone by 2100, Study Finds.” Mongabay. 2018:
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  • Svenssonn, Magdalena S. and Luhrs, Averee, M. “Behaviour of Pottos and Angwantibos.” Evolution, Ecology, and Conservation of Lorises and Pottos edited by K. A. I. Nekaris & Anne M. Burrows (2020): https://radar.brookes.ac.uk/radar/file/f4f48f93-fa5f-4796-952f-bdce4ff9df8f/1/Behaviour%20of%20pottos%20and%20Angwantibos%20-%202019%20-%20Svensson%20Luhrs.pdf
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Written by Kathleen Downey, November 2021