| White-faced saki | |
|---|---|
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| Male atSingapore Zoo | |
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| Female atPhiladelphia Zoo | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Suborder: | Haplorhini |
| Infraorder: | Simiiformes |
| Family: | Pitheciidae |
| Genus: | Pithecia |
| Species: | P. pithecia |
| Binomial name | |
| Pithecia pithecia | |
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| White-faced saki range | |
| Synonyms | |
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Thewhite-faced saki (Pithecia pithecia), is a species ofNew Worldsaki monkey. The small bodiedneotropicalprimate can be found inBrazil,French Guiana,Guyana,Suriname, andVenezuela. This species feeds mostly onfruits,nuts,seeds, andinsects. Although it is anarboreal species and is a specialist ofbrachiation, it is alsoterrestrial whenforaging. Typicallife expectancy is around 14 years in its natural habitat, although individuals have been recorded to live up to 36 years incaptivity. The white faced saki isactive in the day and sleeps highly elevated (15–20 m (49–66 ft)) in trees with many leaves to shelter from weather and flyingpredators.[2]
A formerly recognizedsubspecies,P. p. chrysocephala,[3] was elevated to full species status asP. chrysocephala in 2014.[4]
Pairs of white-faced saki onlybreed once a year, but do not breed seasonally. Estimated typical breeding season is through August and September, but white-faced sakis have been observed breeding in March, April, and June. Breedings are typically not private and are sometimes even done with other group members watching. Regardless of when or howreproduction occurs, a white-faced saki female only gives birth to oneoffspring at a time. Peak birth months typically occur between February and June.[5][6] In captivity, female white-faced sakis experienceovarian cycles of approximately 17 days, and agestational period of 20–21 weeks. Following birth, the mother undergoes a period of lactationally-inducedinfertility lasting 23 weeks on average.[7][2] Once an infant is born, the father spends a great deal of time around it and the mother, likely to protect the two from predators. During this time the mother grooms and takes care of itsoffspring until it becomes independent.[8] Malepaternal care on the other hand does not exist at all. Once it is independent, the offspring usually stays and contributes as a member of the group it was born in. Mature females that are still housed by their parents do not participate in reproduction. White-faced saki practice bothmonogamy andpolygamy, and are defensive when it comes to keeping other groups away from their females. As such, there are only two objectives to the white-faced saki mating system: 1) exclude outsider groups from accessing their females and 2) reduce competition within the group over females.[6]
White-faced sakis display noticeablesexual dimorphism incoloration. Females have shorter hair than males, with brownish-grey fur and white or pale brown stripes around the corners of the nose and mouth. Males, on the other hand, have blacker fur, with a reddish-white forehead, face, and throat. Their faces are much whiter than those of females.[4][2] When compared in size, there is little to no difference between a male and a female white-faced saki. In the species, both genders have relatively small bodies with males typically weighing in around 1.73 kg (3.8 lb) and females weighing in around 1.52 kg (3.4 lb).[6] In terms ofhierarchy, males are clearly favored within the group and its social bonds. Typically, the oldest male is the most dominant in a group.[6] Young saki males are often identified as females because of their sometimes "grizzling"dorsal hair and orangish bellies. It is at approximately 2 months of age when males and females begin to show differences, although it gradually becomes obvious over a few years.[4]
The white-faced saki typically exhibitsshy behavior. It is most active during the early morning and mid-afternoon, and can be found in theunderstory and lowercanopy of therainforest.[5] Males are usually more active than females.[9] At night, the white-faced saki typically migrates uphills to higher altitudes to sleep near the tops of trees. It typically changes its sleeping site every night except on rare occasions. The white-faced saki separates themselves into small family-like groups.[5] ASouth American study shows that groups can range from 2-12 group members, with higher numbers typically occurring (but not exclusively) inGuyana.[9] Most widespread observations conclude that the white-faced saki travels in small groups of 2 and 3, which usually is made up of the bonded parents and their offspring.[10][11] It is believed that it practices both monogamy and polygamy. It is uncertain which one is practiced more, but single male and single female white-faced saki bonds are the strongest bonds witnessed within the groups.[5] The white-faced saki typically strengthens and demonstrates this bond throughgrooming. However, only the females groom males, and the males do not reciprocate. This practice occurs less frequently after an infant is born. As the child becomes more independent, the father and mother spend less time together, and the mother grooms the father less. Male-male bonds between white-faced saki are the weakest. When polygamy is practiced within groups, competition between members can arise. In some cases, members may even interrupt one another while reproduction is occurring.[6][8] These conflicts that occur within groups are nowhere near as intense as the conflicts that occur between two different groups. White-faced sakis are typically peaceful when in the presence of other species of primates, but when in the presence of a different group of white-faced sakis, they become very hostile. These encounters usually lead to standoffs and loud calls between groups.[5] At times these standoffs can even lead to white-faced sakis chasing one another from tree to tree, causing deaths of some participants who have fallen out of a tree. The reason behind this hostile behavior between groups is usually over access to females. White-faced sakis want to keep access to females exclusive to their group. However, altercations between groups can also occur over resources and food. Even though groups are typically hostile to white-faced sakis outside the group, they do sometimes allow immigrant white-faced sakis to become members of the group.[6][8]
The white-faced saki differs from many other primates including its close relative,Chiropotes satanas, in that it is predominantly aleaper.[12] The white-faced saki is considered one of the greatest leapers ofneotropical primates. It is so good at leaping that it was given the nickname "mono volador" (flying monkey).[13] The white-faced saki'sskeleton accounts for their skill with its manymorphologies associated with leaping.[12] Its longhind limbs allow it to propel itself from tree to tree. Between leaps, the white-faced saki uses its average lengthforelimbs to make a series of rapid hand holds that allow it to pull itself and change direction. It is considered to be an awkward quadrupedal walker and runner. The white-faced saki rarely uses any suspensory behavior like other primates and usually eats in a seated or clinging position.[13] Leaping accounts for over 70% of white-faced saki locomotion behavior.Quadrupedal walking/running accounts for 25% of locomotive behavior, while climbing accounted for the remaining 5%.[12]
This picky primate travels distances of 0.5 to 1.25 mi (0.8 to 2.0 km) in search of food or other resources.[10] The white-faced saki has a mixed diet of fruits,leaves, seeds, flowers, insects,honey, and small animals.[2] It is primarily aseed predator, with 60% or more of its diet consisting of seeds. As such, its average monthly intake oflipids is extremely high compared to other fruit consuming animals. Its lipid intake is 4 times higher than otherfrugivores. Itsprotein intake is 2-3 times lower, and its fiber intake is slightly higher than other frugivores. Its specializeddental anatomy consisting of largecanines allows it to bite into and open up hard or protected fruit. It normally consumes the seeds of unripe/immature fruit. When it does eat the flesh of fruit, it comes from ripe/mature fruit. After seeds, young leaves are the second most important food resource to the white-faced saki. In a Venezuelan study, researchers placed out two groups of leaves. One group included youngimmature leaves, and the other group included developed mature leaves. At the end of the study, it was observed that the white-faced saki only ate out of the group of young leaves and did not or rarely ate out of the group of mature leaves. In the same study, it was also established that the white-faced saki eats insects more regularly during thewet seasons of therainforest.[14] On other occasions, the white-faced saki has been observed crawling into hollow portions of trees and eating bats where they roost.[8] It typically get most of its protein from immature fruit seeds, and its lipids from ripe fruit. It also eats a variety of maturedrupes that give it its free simplesugars andfiber. There is little variation in its sources of protein and sugars, but there is great variation in where it gets its lipids.[14]
If a predator is near,alarm calls, which have been observed to last from 1.2 to 88 minutes, will be sounded by an initial white-faced saki and then continuallyechoed by others to spread the warning. They will then puff their bodies up and stomp their feet on the ground or trees in an attempt to intimidate the threat.[11][10] They are small primates and dwell in the branches of trees, so one of their biggest predator threats are large birds such ashawks andharpy eagles. In the face of danger, the white-faced saki will emit warning calls to others or freeze if in the canopy in an attempt to move down where it is out of sight. The predator response of the white-face saki is based on what type of threat they are facing: if it is a smaller, easily overpowered threat, the group will participate in a behavior called"mobbing" to scare the predator away, but if the threat is larger, such as an eagle, they will refrain from warning calls and descend out of sight into the lower canopy. Otherterrestrial andaquatic predators includetayras,jaguars,pumas,green anacondas,ocelots,red-tailed boas, and even largemustelids, which are usually threats to the young and elderly.[10]
