White-nosed Saki (Chiropotes albinasus)
The average body mass for the male white-nosed saki is about 3.1 kilograms, and for the female it is about 2.5 kilograms (Ayres, 1989). The color of the hair is black except for the nose which has white colored hair. This species has broad canines to assist in the eating of fruit with a tough pericarp and also has strong jaw muscles to assist. The scrotum of the male is pink in color. The male of this species does not possess a baculum as other primate species do (Hershkovitz, 1993). The penis of the male possesses spines which are large and hooked (Hershkovitz, 1993). There is little sexual dimorphism of the canine teeth (Kay et al., 1988). The premolars of this species have crenulated occlusal surfaces (Kinzey, 1992). The white-nosed saki has a pelage color which is described as being silky black with a white nose (van Roosmalen et al., 1981). This species is characterized by a beard and temporal swellings (van Roosmalen et al., 1981). This species has a less developed beard as compared to Chiropotes satanas (van Roosmalen et al., 1981). The tail of this species is not prehensile as compared to other New World primates (van Roosmalen et al., 1981). The tail of the infant however, is prehensile until the age of 2 months (van Roosmalen et al., 1981).
The white-nosed saki is found in the country of Brazil, south of the Amazon River and between the rivers Xingu and Madeira (Ayres, 1989). This species lives in high forests, primary forests, and terra firma forests (Ayres, 1989). This species has also been shown to occasionally inhabit igapo forest (Wallace et al., 1996).
The white-nosed saki is primarily a sclerocarpic frugivore (Ayres, 1989). In the Aripuana River region, fruit from trees made up 87% of the diet, while fruit from lianas made up 10% of the diet (Ayres, 1989). In the Aripuana River region 54 % of the diet came from fruit pulp and aril, 36% from immature seeds, 3% from flowers, and 7% from bark, insects, and leaves (Ayres, 1989). The most important fruit species consumed is Astrocaryum vulgare (Palmae) (Ayres, 1989). The most important plant families at the Aripuana River region are Palmae, Sapotaceae, and Leguminosae (Ayres, 1989). During the rainy season seeds from fruits account for 12% of the diet while during the dry season they account for 82% of the diet (Ayres, 1989). Mesocarps from mature fruit account for 79% of the diet during the rainy season and 18% during the dry season (Ayres, 1989). The white-nosed saki seems to prefer fruit that are rich in lipids, proteins, and carotenoids (Ayres, 1989). This species to a lesser extent forages for leaves and insects. The white-nosed saki forages on unripe fruit that other primates would only eat when ripe (Kinzey and Norconk, 1990). Most of the insects this species consumes are soft-bodied (Kinzey, 1997). The most insects consumed were found to be larvae of Lepidopterans (Ayres, 1989).
The group size for this species ranges from 19 to 30 individuals (Ayres, 1989). This species never uses the same tree for consecutive nights and sleeps on medium size branches of emergent trees (Kinzey, 1997). This species forages in the upper part of the canopy (Ayres, 1989). This species moves rapidly between widely scattered trees and engages in rapid feeding bouts (Ayres, 1989). The large multimale groups travel together between feeding sources then split when arriving at the food source (Ayres, 1989). When foraging on trees that are narrow, individuals will line up and remove the fruit to larger trees so that all members of the group can have a chance to feed (Ayres, 1989). This species sometimes forms mixed-species associations with Cebus apella (van Roosmalen et al., 1981). This is an arboreal and a diurnal species.
The white-nosed saki moves through the forest canopy quadrupedally (Fleagle, 1988). This species uses hindlimb suspension when feeding (Fleagle, 1988). This species also occasionally leaps from a pronograde position and lands on the terminal branch of a neighboring tree (Walker, 1993). Leaping is not as important in this species as it is in Pithecia pithecia (Walker, 1998). When leaping this species usually takes-off from horizontal or angled supports that are less than 2 centimeters in diameter and lands upon supports of multiple terminal branches that are also less than 2 centimeters in diameter (Walker, 1998). When leaping this species first starts to move quadrupedally, then takes-off from a horizontal or angled support, using the momentum gained to assist in the leap (Walker, 1998). Usually this species lands when leaping on all fours (both the hands and feet) (Walker, 1998). The white-nosed saki occasionally climbs in the head-down posture (van Roosmalen et al., 1981).
The white-nosed saki has a multimale social system, containing unequal numbers of males and females (Kinzey, 1997). Grooming does occur amongst members in the social group (van Roosmalen et al., 1981). The large groups split into smaller groups during the day for foraging (Fleagle, 1988).
high-pitch whistle: This call serves as a contact signal and a more intense version serves as a alarm call (van Roosmalen et al., 1981). This call starts out as a sharp penetrating whistle lasting for one second and then cuts off (van Roosmalen et al., 1981).
weak chirp: This call is heard when eating and also when satisfied (van Roosmalen et al., 1981).
tail-wagging: This serves as a displacement activity and a silent contact signal (van Roosmalen et al., 1981).
piloerection: This is where hair on the head of an individual will stand straight up (van Roosmalen et al., 1981). This occurs when an individual is excited (van Roosmalen et al., 1981).
The white-nosed saki gives birth to a single offspring. This species does not have a birth season, with the majority of the births occurring from February to March and from August to September (Robinson et al., 1987). The anogenital region of the female, in particular the labia, changes to a bright red when the female is in estrus. During estrus the female will present to male, lifting her tail so that the bright red anogenital region shows (van Roosmalen et al., 1981).
After the birth of the young, the mother does not eat the afterbirth like other primate species (van Roosmalen et al., 1981). After nursing the infant will urinate and defecate and the mother will lift the tail of the infant to assist in removing feces (van Roosmalen et al., 1981). The infant moves on its own and stops nursing around three months of age (van Roosmalen et al., 1981).
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.
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Fleagle, J. G. 1988. Primate Adaptation and Evolution. Academic Press.
Hershkovitz, P. 1993. Male external genitalia of non-prehensile tailed South American monkeys. Part I. Subfamily Pitheciinae, Family Cebidae. Fieldiana Zoology. New Series, No. 73. 1-17.
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Kinzey, W.G. and Norconk, M.A. 1990. Hardness as a Basis of Fruit Choice in Two Sympatric Primates. American Journal of Physical Anthropology Vol. 81(1), 5-15.
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van Roosmalen, M.G.M., Mittermeier, R.A., and Milton, K. 1981. The Bearded Sakis, Genus Chiropotes. in Ecology and Behavior of Neotropical Primates. eds. A.F. Coimbra-Filho and R.A. Mittermeier. Academia Brasileira de Ciencias.
Walker, S.E. 1993. Positional Adaptations and Ecology of the Pitheciini. Unpublished Ph.D. dissertation, City University of New York.
Walker, S.E. Fine-grained differences within positional categories. In Primate Locomotion. eds. E. Strasser, J.G. Fleagle, A. Rosenberger, H. McHenry. Plenum Press: New York.
Wallace, R.B., Painter, R.L.E., Taber, A.B., and Ayres, J.M. 1996. Notes on a distributional river boundary and southern range extension for two species of Amazonian primates. Neotropical Primates. Vol. 4(4), 149-151.
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