Geographic Distribution and Habitat
The bearded saki (Chiropotes chiropotes) also goes by the common names Humboldt bearded saki, red-backed bearded saki, red-backed saki, and tawny-olive bearded saki. They are native to the South American countries of Brazil, French Guiana, Guyana, Suriname, and Venezuela. They prefer to make their homes in upper primary rainforests, often near streams or rivers, although they can also be found in low and secondary forests. They rarely reside on the edges of habitats, preferring to be deep in undisturbed forest.
There is debate over the taxonomy of Chiropotes. As of this writing, the Internation Union for Conservation of Nature’s Red List of Threatened Species recognizes five Chiropotes species: the bearded saki, C. chiropotes (the subject of this profile), the white-nosed saki, C. albinasus, the red-brown bearded saki, C. sagulatus, Uta Hick’s bearded saki, C. utahicki, and the the black bearded saki, C. satanas. Other sources recognize yet another species, the brown-backed bearded sakis, C. israelita. Some sources treat C. chiropotes and C. israelita as synonymous. Some treat C. sagulatus and C. israelita as synonymous.
Both C. israelita and C. chiropotes were formerly considered synonymous subspecies of C. satanas. However, in 2003, a study provided morphologic and molecular evidence that both may be deserving of full species status. Some sources accept this study and treat both as separate species, while others side with the IUCN and consider C. chiropotes a full species, with C. israelita a synonym.
The controversies among scientists continue. Until their resolution, it is fair to say that this genus is very much “under construction” and subject to change as more evidence for or against elevating populations to species status comes to light.
Size, Weight, and Lifespan
Bearded sakis are medium-sized monkeys, with an average weight of 5.6 lbs (2.6 kg) for females and 6.8 lbs (3 kg) for males. Their average head and body length is between 16 and 18 inches (41–46 cm), with males on the longer side. Bearded sakis have been known to survive into their late teens in captivity.
Bearded sakis are highly unique in appearance. Their most prominent features are their beard and head hair. The hair on the top of their head, called “coronal tufts,” is puffy and round and often forms two distinct spheres. On some individuals, this hair pattern is so prominent that they appear to have two black tennis balls strapped to their head like a helmet! Their beard only adds to this effect, as it too is very round and bulbous. Their head and face are black, and their noses are very flat. Like other primates, their eyes are situated on the front of their face, providing them binocular vision. Their arms and legs are long, agile, and black. Their tail is covered in long, black hair, giving it an almost fox-like shape. The hair on their shoulders and upper back is often longer than the rest of their body, which can give them the appearance of a cape. Their back is a rusty orange color, a primary distinguishing characteristic from other species in their genus. Bearded sakis exhibit mild sexual dimorphism: males are often larger and have a longer and more prominent beard than females.
Bearded sakis are primarily frugivorous (fruit-eating), with seeds comprising the largest portion of their diet, along with fleshy fruits and nuts. They supplement this diet with insects. They are very well adapted to their seed-heavy diet, and can use their powerful teeth and jaws to efficiently open hard-shelled fruits. They eat these fruits by gnawing a hole at the top then use their large incisors like a can opener to pop the shell open. Seed-eating is more common during the dry months, while more fruits are eaten in the wet months. They aren’t picky about the ripeness of the fruits they eat, and the only period of food scarcity they experience is the time during seasonal transitions, and they account for this by spending more time foraging during these parts of the year. Bearded sakis have also been known to eat soil from termite nests.
Behavior and Lifestyle
Bearded sakis are active from right after sunrise to right before sunset, and spend their entire lives in trees. A study based in Venezuela found that they spend their waking hours feeding 37% of the time, foraging 10%, traveling 19%, nesting 21%, and doing other activities the remainder of the time. They range about 0.7 to 2 miles (1.1–3.2 km) per day. Because their food sources are usually abundant, they move rapidly from food tree to food tree, stopping to feed for a short time before moving on. They are very agile, using their powerful hind legs to leap long distances. They often eat while suspended from their hind legs, with their non-prehensile tail draped over a branch for additional support. It is believed that they sleep high in the trees, often with their tail curled around their body. A study of a closely related species, black-bearded sakis (C. satanas), found that they move quadrupedally (on all fours) about 80% of the time, leaping 18%, and climbing only rarely. While leaping, they begin their jump while already moving, not while standing, and land on all fours. They usually travel and feed in the upper parts of the canopy. When the monkeys are forced to inhabit small fragments of forest, their travel distance is shortened and they revisit the same food trees more often than when living in intact forest.
Bearded sakis are born with prehensile tails, which they retain for about the first two months of life. This allows them to cling to their mother’s body. After this time, their tail loses its prehensility.
Bearded sakis associate in large troops of 20–30 members, although they break into smaller groups of about 9 to travel and forage, an arrangement known as a “fission-fusion” social structure. Foraging groups move very quickly, a benefit afforded to them because of their plentiful food sources. Individuals can actually become lost from their foraging groups, sometimes being separated for days or weeks. Home range size has been recorded between 0.5 and 2.2 sq miles (1.42–5.6 sq km).
Bearded sakis communicate vocally using whistles and twitters, as well as with a variety of body language signals. When silence is important, such as to communicate the presence of a predator, they wag their tails. They are also known to use olfactory communication.
Reproduction and Family
Little is known about the bearded saki’s mating system. Based on information available for the closely related brown-bearded saki, bearded sakis are likely not monogamous. There is little information about their breeding cycles, although births seem to be most common at the beginning of the rainy season in December and January, which is also when several important food trees begin their fruiting season. When she is receptive to breeding, a female’s anogenital region turns bright red, and she will present this to males as a signal by lying prone in front of them and lifting her rump to expose the red area. She also makes a purring noise to indicate her receptivity to breeding. After mating, bearded sakis have about a five month gestation period, after which a mother gives birth to a single offspring. Very little data has been recorded about parenting among bearded sakis, although based on limited observations from related species, babies likely begin gaining independence at about three months of age. Before that, their mother provides the bulk of their care.
Bearded sakis are known as “seed predators” because, unlike many other frugivorous primates that excrete intact seeds in their droppings where they later germinate and grow, bearded sakis fully digest most of the seeds they eat. That being said, they can and do certainly drop fruit and seeds that later grow into plants. One study found that seeds comprise almost three-quarters of their diet, and another found that they consume seeds from over 100 plant species. They are sympatric with numerous other primates. Because they eat fruits and seeds at all different stages of ripeness, they rarely have competition for their food source. Occasionally, however, there is competition with capuchin monkeys (Cebus spp.) and howler monkeys (Alouatta spp.) when they are both feeding at the same tree, resulting in displacement or aggression. These species eat the same fruits but only when ripe. They also compete with other seed predators such as macaws and other parrots. Recorded predators of bearded sakis include boa constrictors and harpy eagles.
Fortunately, bearded saki populations are very stable and, as such, they are considered Least Concern by the IUCN (2015). They live in well preserved areas of the Amazon rainforest where human population densities are low. They are occasionally subject to hunting pressures from humans, but this is generally low and has a negligible impact on population.
While bearded sakis fortunately live in well-protected habitat, that doesn’t mean it’s not under threat. Climate change is already having impacts on the Amazon rainforest and is expected to continue. By 2050, temperatures in the Amazon are expected to increase by 3.6 to 5.4 degrees Fahrenheit (2 to 3 degrees Celsius) and rainfall is expected to decrease during the dry months. While those may not seem like substantial changes, even relatively small changes in climate can have massive impacts on habitats—and by extension, biodiversity. If habitats change too drastically and quickly for species, including bearded sakis, to adapt, it, unfortunately, won’t matter how many habitat protections are in place. Brazil’s National Space Research Institute calculated that climate change could turn between 30 and 60% of the Amazon rainforest into dry savanna.
Bearded sakis are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which limits international trade of species. Forty-four percent of the Amazon rainforest is covered by protected areas, and while some of these areas are subject to poor management, the area of the bearded saki’s range is known to be particularly well-preserved and not under immediate threat of development or deforestation.
- Bonvicino, C., Boubli, J., Otazú, I., Almeida, F., Nascimento, F., Coura, J. and Seuánez, H. 2003. Morphologic, karyotypic, and molecular evidence of a new form of Chiropotes (primates, pitheciinae). Am. J. Primatol., 61: 123-133. https://doi.org/10.1002/ajp.10115
- Boyle, S.A., Lourenço, W.C., da Silva, L.R. et al. 2009. Travel and Spatial Patterns Change When Chiropotes satanas chiropotes Inhabit Forest Fragments. Int J Primatol 30, 515–531. https://doi.org/10.1007/s10764-009-9357-y
- Norconk, M. 1994. Challenge of Neotropical Frugivory: Travel Patterns of Spider Monkeys and Bearded Sakis. American Journal of Primatology, 34(2): 171-183.
- Van Roosmalen, M.G.M., Mittermeier, R.A. and Fleagle, J.G. 1988. Diet of the northern bearded saki (Chiropotes satanas chiropotes): A neotropical seed predator. Am. J. Primatol., 14: 11-35. https://doi.org/10.1002/ajp.1350140103
Written by K. Clare Quinlan, December 2021