Geographic Distribution and Habitat
The white-nosed saki is endemic to the south-central Amazon rainforest in Brazil, particularly between the rivers Xingu and Madeira and farther south to the Guaporé River in Rondônia. They prefer to be in high forests, especially high terra firme forests. White-nosed sakis can be found in flooded forests (also known as inundated forests), far away from rivers, and in dense and moist forests. Occasionally they have been observed in fragmented areas, especially in vegetation between the transition of forest to savanna.
This species prefers to stay at the crown level in trees, away from predators such as jaguars and humans.
Size, Weight, and Lifespan
White-nosed sakis are medium-sized monkeys. Male head-to-body length often ranges between 17 and 19 in (42–48 cm); females are slightly smaller and typically measure around 16.5 in (41.8 cm). The tail is sometimes longer than the head-to-body length, measuring around 12–20 in (30.5–51 cm).
Males weigh around 7.1 lb (3.22 kg), while females weigh 5–6 lb (2.3–2.7 kg).
White-nosed sakis can live up to 26.5 years in the wild.
Able to grasp or hold objects.
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Despite their name, white-nosed sakis actually have a reddish-pinkish nose and upper lip with very fine (hardly visible) white hairs. This species has a unique appearance since no other species in the genus Chiropotes has this brightly colored muzzle. They have a black silky coat and a long bushy tail, which is used for balance. The tail of an infant is prehensile up until two months of age. The white-nosed saki has a beard—though it’s less developed than that of the black-bearded saki (Chiropates satanas)—and temporal swellings. Their large canine teeth allow them to easily access tough fruits and seeds.
The white-nosed saki is mainly a frugivore. They enjoy eating hard-shelled fruits and seeds as a large portion of their diet. In the Aripuana River region of Brazil, 87% of the white-nosed saki diet is fruit from trees. In addition, scientists have found that 54% of their diet comes from fruit pulp and aril (which is similar to a seed pod). The rest of their diet is a mixture of seeds, nuts, bark, flowers, insects, and leaves.
One of the most important fruit species consumed is Astrocaryum vulgare, which is a type of palm tree native to the Amazon rainforest. The fruit from this palm is also used for biodiesel production. White-nosed sakis seem to prefer fruits that are rich in lipids, proteins, and carotenoids. Carotenoids give fruits and vegetables orange, yellow, and bright-red pigments, and are thought to provide some health benefits. This species tends to not only forage for leaves or insects, but also for unripe fruits, which other primate species will only eat ripe.
Behavior and Lifestyle
The white-nosed saki is a diurnal species (active during daylight hours), however, not much is known about their behavior and ecology since they are not easily observed in the wild because they live so high in and above the canopy. They are predominantly arboreal (tree-dwelling), and move quadrupedally (on all fours) throughout the forest. White-nosed sakis are outfitted with longer hindlimbs than forelimbs and are occasional leapers; they leap from a pronograde position—that is, when the body is parallel to the ground or in a quadrupedal position—and land on thin terminal branches. They can also climb trees in a head-down posture, like a squirrel. They do not use their tails to grip or swing; instead they use them for balance while moving through the trees.
The white-nosed saki has a multi-male social system. A group consists of about equal numbers of males and females. Saki monkeys are highly territorial and will defend their homes against other saki groups.
Sakis rarely ever sleep in the same tree for two consecutive days.
Most of the insects white-nosed sakis consume are soft-bodied.
Despite their name, white-nosed sakis actually have bright reddish-pinkish noses with faint white hairs.
White-nosed sakis often live in large groups of 18 to 30 individuals. They sleep on medium-sized branches on the emergent layer (or highest level) of the trees, and forage in the canopy below. Saki monkeys’ main reason for traveling is in search of food. They move quickly between the trees and engage in rapid feeding bouts. During the day, large groups split into smaller groups for foraging. Most of the time, large multi-male groups travel together between feeding sources then split once they arrive at the food source. White-nosed sakis line up when foraging on narrow tree branches so all members of the troop have a chance to feed on fruits.
White-nosed sakis sometimes form associations with black-capped capuchins (Cebus apella). These associations are not well studied, but are believed to be beneficial for reducing predation risk, finding food, and increasing foraging efficiency.
There have not been many extensive studies on the vocalizations of white-nosed sakis. However, some vocalizations have been recorded, such as a whistle, chirp, and shrill call. They use a high-pitch whistle as a contact signal and as an alarm. The call starts out as a sharp, penetrating whistle that lasts for about a second then stops. A shrill-like call is emitted when they feel disturbed. A weak chirp is mainly used when eating or when satisfied. Purring sounds are emitted by the female prior to mating and by the male during mating.
White-nosed sakis also uses visual communication, such as tail wagging, which indicates that they are confused or uncertain about something. When excited, they communicate via piloerection, which is when the hair on the head of an individual stands straight up.
Little is known about the mating system and reproductive cycles of saki monkeys, although it is known that white-nosed sakis breed seasonally. When a female is ready to mate, her anogenital region becomes bright red. The majority of births occur between February and March and between August and September, and females give birth to one infant per year. The gestation period is about five months.
Much of the information on reproduction is based on captive observations. Their remote territories preclude wild observations. Captive observations tell us that young sakis begin to become independent of their mothers at about three months of age. At four years, white-nosed sakis are fully mature.
Most of the parental care comes from the mother. Little is known about the males’ role with infants, especially in the wild. The mother nurses the baby and carries the young until he or she is weaned.
As frugivores, the white-nosed saki plays a role in distributing seeds of fruiting trees.
The white-nosed saki is listed as Vulnerable by the International Union for Conservation of Nature Red List of Threatened Species (IUCN, 2020). The main threats are deforestation, forest fragmentation through logging, cattle ranching, agriculture, rural settlements, subsistence hunting, improvement of road infrastructure, and improvement of energy infrastructure (i.e., the construction of hydroeletric plants on the Rios Teles Pires, Juruena, Tapajós and Madeira). They are also hunted for their tails, which are used as dusters.
Per the IUCN, a population reduction of 30% or more is inferred over the course of 30 years or three generations. Their data suggests that, should forest loss continue at the same rate that has impacted the previous generation (2009-2018), 15% or more of this species’ suitable habitat is likely to be lost by the year 2048. Combined with continued evidence of subsistence hunting, these threats push the white-nosed saki above the threshold for Vulnerable status.
The white-nosed saki is listed on the Convention on International Trade in Endangered Species (CITES) Appendix I. They are found in Amazônia National Park and Tapajós National Forest. In order to help save the species, many conservation actions are needed. Although there are international trade controls on the white-nosed saki, much more monitoring is needed for their protection. Land and harvest management is also essential to control the overuse of agriculture and clearing of land. In addition, more research is needed on the species itself to understand their responses to such threats and what conservation actions would best preserve them.
- Ayres, J.M. 1989. Comparative Feeding Ecology of the Uakari and Bearded Saki, Cacajao and Chiropotes. Journal of Human Evolution Vol. 18(7), 697-716.
- Walker, S.E. 1993. Positional Adaptations and Ecology of the Pitheciini. Unpublished Ph.D. dissertation, City University of New York.
- Walker, S.E. 1998. Fine-grained differences within positional categories. In Primate Locomotion. eds. E. Strasser, J.G. Fleagle, A. Rosenberger, H. McHenry. Plenum Press: New York.
Written by Tara Covert, December 2018