Chiropotes satanas
brown-bearded saki

Chiropotes satanas (brown-bearded saki) is found throughout much of northern Amazonia and the Guianas. There are two recognized subspecies: C. s. satanas is endemic to Brazil occupying a small area around the Tocantin river near the mouth of the Amazon, C. s. chiropotes occurs more widely north of the Amazon river and east of the Negro and Orinoco rivers. The total geographic range of C. satanas has been estimated at 62,911 square kilometers. (Flannery, 2007; Fleagle, 1999; Lehman, 2004; van Roosmalen, et al., 1981; Veiga and Ferrari, 2006)

Chiropotes satanas is typically found in primary tropical rainforests. In Brazil, members of this species are found in terra firma forests and occasionally in regenerating forests. In Suriname, C. satanas has been seen in rain forests, mountain savannah forests and occasionally in gallery forests. They rarely descend to lower canopy levels and the forest floor. Chiropotes satanas individuals spend 60% of their time in the middle and upper levels of the forest canopy. (Flannery, 2007; Lehman, 2004; van Roosmalen, et al., 1981; Veiga and Ferrari, 2006)

Brown-bearded sakis are marked by bulbous temporal swellings, long bushy tails, and short body hair unlike the long, shaggy hair of their relatives in the genera Cacajao and Pithecia. Brown-bearded sakis are distinguished from the closely related Chiropotes albinasus by their larger black beards and their black noses. The two identified subspecies are primarily black except for the light yellowish-brown to ochraceous coloring on the back of C. s. chiropotes and the dark brown to black back and shoulders of C. s. satanas. In both subspecies, as well as in C. albinasus, males have distinctive, pink scrota and females have pink vaginal lips. Black-bearded sakis are slightly sexually dimorphic with an average weight of 3 kg in males and 2.6 kg in females. Head and body length ranges from 327 to 480 mm and tail length from 370 to 463 mm. Their hindlimbs are slightly longer than their forelimbs, resulting in an intermembral index of 83. They have a small thumb lacking true opposability. The foot tends to deviate laterally and the tarsal bones have increased mobility, a trait associated with their habit of hindlimb suspension while feeding. (Flannery, 2007; Fleagle and Meldrum, 1988; Fleagle, 1999; Van Roosmalen, et al., 1988; van Roosmalen, et al., 1981; Walker, 2005)

The jaws of brown-bearded sakis have specialized anterior dentition for opening thick, woody, husked fruits. Adapted for powerful crushing, they have strong jaw muscles, low, flat molar teeth, broad canines, a deep robust mandible, and a dense maxilla without a maxillary sinus. (Flannery, 2007; Fleagle and Meldrum, 1988; Fleagle, 1999; Van Roosmalen, et al., 1988; van Roosmalen, et al., 1981; Walker, 2005)

Little is currently known about the mating system of Chiropotes satanas in the wild. They live and interact mainly in multi-male multi-female social groups, monogamous groups have been observed rarely. (Fleagle, 1999; Kay, et al., 1988; Peetz, 2000; van Roosmalen, et al., 1981)

Mating has been observed in captivity although it was between a female Chiropotes albinasus and a male Chiropotes satanas, producing a hybrid offspring. Here it was observed that the female’s anogenital region became bright red to indicate sexual receptivity and that she made this visible to the male by lying in front of him and lifting her to exposing the red color. She also made a purring vocalization similar to one made by the male during mating. (Fleagle, 1999; Kay, et al., 1988; Peetz, 2000; van Roosmalen, et al., 1981)

There is little information available on the reproductive cycles of Chiropotes satanas in the wild. Birth seem to occur at the beginning of the rainy season, in December or January. This coincides with the beginning of the fruiting season of several important species of Eschweilera trees that brown-bearded sakis exploit for food. (Flannery, 2007; Van Roosmalen, et al., 1988; van Roosmalen, et al., 1981)

All other reproduction information for C. satanus is based on observations of a hybrid born to a female Chiropotes albinasus and a male C. satanas in captivity. These observations estimate a gestation period of four to five months. The hybrid offspring was weaned and capable of independent locomotion by the age of three months. (Flannery, 2007; Van Roosmalen, et al., 1988; van Roosmalen, et al., 1981)

An interesting trait of C. satanas infants is their prehensile tail. Observed in the wild as well as with the captive hybrid, the tail is prehensile for about the first two months of life. It is used to cling to the mother. The tail ceases being prehensile at about 2 months old. (Flannery, 2007; Van Roosmalen, et al., 1988; van Roosmalen, et al., 1981)

Most of the parental care comes from the mother. The reaction of a male Chiropotes satanas to the cries of his hybrid infant in captivity show a level of concern that could translate in the wild to pre-weaning protection. This cannot be truly known given that the offspring is a hybrid and in captivity forced to be in close contact. The mother nurses the infant and carries the infant on her until the young are weaned. Infants show some association with the mother after weaning, at 2 to 3 months of age, often retreating to her for protection when startled. (Fleagle, 1999; van Roosmalen, et al., 1981)

There have been limited long term studies on Chiropotes satanas, so no available information on lifespan in this species. Related species have been recorded living up to 20 years.

Chiropotes satanas live in relatively large multi-male multi-female groups of about 8 to 40 individuals. Larger groups split into smaller troops of about nine while foraging. While foraging the troop moves fast, stopping briefly for intense feeding periods. Troops move so rapidly from one cluster of feeding trees to the next that occasionally, single individuals get lost from their group for days or weeks. In these cases the lost monkey often temporarily joins groups of Ateles or mixed groups of Cebus apella and Saimiri sciureus. Brown-bearded sakis use a variety of sleeping trees and do not return to the same sleeping site each night. Locomotion in C. satanas is characterized as arboreal quadrupedalism with some leaping and climbing. Climbing only accounts for 2% of locomotion, leaping accounts for 18%, and quadrupedal branch walking and running account for the vast majority of locomotion at 80%. Brown-bearded sakis typically feed in a pronograde, quadrupedal position but also commonly use hindlimb suspension postures to extend their reach to otherwise inaccessible fruits. In hindlimb suspension brown-bearded sakis typically drape their long, non-prehensile tails over a branch for added support. While resting on horizontal boughs or thick branches adults wave their tails to give signals. When on smaller branches, tail waiving is used for balance. The tail of C. satanas is interesting in that it is prehensile until about two months of age and then becomes non-prehensile. (Flannery, 2007; Fleagle and Meldrum, 1988; Fleagle, 1999; Norconk, 1994; Peetz, 2000; Van Roosmalen, et al., 1988; van Roosmalen, et al., 1981; Veiga and Ferrari, 2006; Walker, 2005)

An interesting behavior observed in C. satanas is huddling. Characterized by two or more individuals crowding close together or embracing on horizontal supports, huddling behavior is a response to threatening situations like predation avoidance, resource defense, and mate defense. Accompanied by alarm, chirping sounds, and tail wagging, these huddling bouts last an average of 23 seconds. Interestingly, the majority of huddling is done between two males (62%), while none has been observed between two females. Males and females have been observed huddling together in 38% of observations and juveniles have been involved in 16%, usually because of an association with a female. Adult to adult as well as adult to juvenile grooming has been observed in Chiropotes satanas. (Flannery, 2007; Fleagle and Meldrum, 1988; Fleagle, 1999; Norconk, 1994; Peetz, 2000; Van Roosmalen, et al., 1988; van Roosmalen, et al., 1981; Veiga and Ferrari, 2006; Walker, 2005)

Day ranges of Chiropotes satanas have been recorded averaging 2500 to 3500 m. Home range has never accurately been recorded but estimates range from 75 to 250 ha. (Flannery, 2007; Van Roosmalen, et al., 1988; van Roosmalen, et al., 1981)

Black-bearded sakis use vocalizations and body language to communicate. As is the case with many arboreal primates, vocalizing is an important way to keep track of conspecifics in an environment with often limited vision. There have been no extensive studies on vocalizations of Chiropotes satanas, but some repeatedly observed vocalizations have been recorded. Weak chirps are associated with eating and satisfaction, and a shrill vocalization was recorded when a group was eating seasonally abundant caterpillars in eastern Brazilian Amazonia. A high pitch whistle, described as starting off as a sharp penetrating whistle, lasting for about a second and then cutting off, serves as a contact signal while a more intense version serves as an alarm call. A shrill bird like cry is also made when disturbed. Purring vocalizations are emitted by the female prior to mating and by the male while mating. The hybrid offspring infant described above made similar sounds when it wanted to nurse prompting the mother's help in finding the nipple. The infant's vocalization also provoked a similar vocalization from the mother which apparently excited the male. Loud cries by the infant disturbed the mother and father prompting close examination by both parents.

Tail wagging has been observed in a number of contexts. Considered a sign of excitement, it may also serve as a displacement activity and as a silent contact signal. (Flannery, 2007; van Roosmalen, et al., 1981; Veiga and Ferrari, 2006)

Primarily a sclerocarp frugivore, Chiropotes satanas feeds primarily on immature seeds particularly covered in hard pericarp. They have been recorded to eat at least 53 different species of seeds and are especially fond of the Brazil nut family (Lecythidaceae). Their specialized anterior dentition allows them to open very hard fruit for the young, relatively soft seeds. By eating young immature seeds C. satanas not only gets at a resource unavailable to many other primates, but also may avoid toxins that only occur in more mature seeds. The ability to break open hard shells of immature seeds and fruit also gives C. satanas an advantage by allowing them first pick of fruiting trees often not leaving many to ripen to stages that other species can eat. The opening of hard fruits and shells by C. satanas is accomplished by first biting a hole into the fruit at the edge of the operculum, then using it’s procumbent incisors to pop off the operculum to get to the seeds inside. The powerful wedge-shaped canines of C. satanas, rather than the incisors, are used when opening very tough foods with thick, hard seed pods.

The most efficient seed predator of any monkey species, C. satanas> individuals have been observed consuming 66% of their diet in seeds. They compliment this diet with ripe fruit, flowers, leaf stalks, and arthropods. Studies in Brazil, Surinam, and Venezuela showed 10 taxonomic orders of arthropods and 85 different plant species being exploited. The most common arthropods eaten are caterpillars, termites and gall wasps. Arthropod consumption in C. satanas is usually fairly low throughout the year peaking one to three times a year during temporary spikes in prey availability. When capturing prey, C. satanas often exhibit dexterity and agility. For example, individuals can remove gall wasp larvae from galls 4 mm in diameter, and others rest their arms, allow ants to climb onto them, and then eat the ants off their hair.

Captive individuals often drink by cupping their hands to pick up water then suck the fluid from their hands. Although not recently recorded in the wild, it can probably be assumed that this is characteristic of the species since the scientific name Chiropotes, coined by Humboldt, means “hand-drinker.”

Interestingly, geophagy (the ingestion of earth, soil or clay) has been observed on two occasions by C. satanas. In both instances individuals were seen eating a few handfuls of termitaria without any inspection (as they would do when hunting insects) indicating that the ingestion of the termitaria was the purpose. This is thought to be an adaptive behavior for a number of reasons: mineral supplementation, absorption of harmful toxins, and for easing gastrointestinal disorders such as diarrhea and excess stomach acidity.

Brown-bearded sakis spend 130 to 200 minutes a day feeding, not including travel time between food resources. While foraging they split up into smaller feeding units of around nine individuals and move rapidly in a cohesive manner between groups of feeding trees. Once the troop has arrived at a new feeding area they then split up, staying within a radius of 50 to 75 m, well within range of each others vocalizations which they keep up constantly. The pattern of rapidly moving between food trees with periods of relatively short but intense feeding bouts observed in brown-bearded sakis is to be expected of a specialized species concentrating on widely dispersed, seasonal, high protein food sources. (Flannery, 2007; Fleagle and Meldrum, 1988; Fleagle, 1999; Norconk, 1994; Van Roosmalen, et al., 1988; van Roosmalen, et al., 1981; Veiga and Ferrari, 2006; Veiga and Ferrari, 2007)

Brown-bearded sakis avoid predation largely through occupying the highest levels of the forest canopy and through their large body size. Quadrupedal leaping is also a helpful predator avoidance mechanism allowing a speedy and difficult to follow getaway. Harpy eagles, jaguars, and humans are the primary predators of Chiropotes satanas. (Fleagle, 1999; van Roosmalen, et al., 1981; Walker, 2005)

As frugivores, brown-bearded sakis play a role in distributing seeds of fruiting trees. Their role as seed dispersers, however, is decreased by the fact that they eat immature seeds of unripe fruits. Their ability to get at immature seeds in unripe fruits also effects sympatric frugivorous species like Ateles paniscus and Cebus apella who eat some of the same fruits, but only when ripe. Brown-bearded sakis often live sympatrically with several other Platyrrhini species such as Alouatta seniculus, Saimiri sciureus, Saguinus midas, and Pithecia pithecia. (Fleagle and Meldrum, 1988; Fleagle, 1999; Van Roosmalen, et al., 1988)

Some groups of humans benefit from Chiropotes satanas by hunting them for meat and body parts. Humans also may benefit economically from keeping some black-bearded sakis in zoos. (van Roosmalen, et al., 1981)

There are no known adverse effects of Chiropotes satanas on humans.

Chiropotes satanas is considered endangered because of human induced habit degradation and hunting. The United States Endangered Species Act list lists C. satanas as endangered. The CITES appendices has both subspecies under Appendix II since 1977. The formation of protected areas may be improving the prospects for populations of Chiropotes satanas chiropotes.