Ateles chamek

Geographic Range

Ateles chamek , or the black-faced black spider monkey, is found in areas of Peru, Brazil, or Bolivia.

• Biogeographic Regions
• neotropical neotropical

Habitat

Black-faced black spider monkeys can be found in a variety of semi-deciduous lowland forests (including piedmont and cerrado forests which can be dry and have hilly landscapes) in Peru, Brazil and Bolivia. They typically shift their home ranges based on food availability, moving between areas of patchy food resources within these forests. They are typically found in high forest strata, occupying the canopy and sub canopy layers.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• scrub forest scrub forest

Physical Description

The weight of an adult black-faced black spider monkeys typically ranges from 15 to 20 lbs (7 to 9 kgs), and represents some of the largest of the New World monkeys. Black-faced black spider monkeys have a prehensile tail like the other Ateles species that can be used to assist with brachiation. Use of the prehensile tail allows them to be extremely agile through the canopy. They also have four long fingers and a thumb which is short (almost absent).

In the past, black-faced black spider monkeys were often confused with another closely related species, Ateles paniscus , red-faced spider monkeys. Ateles chamek was once thought to be a sub-species of Ateles paniscus . Ateles chamek can be distinguished from the closely related Ateles paniscus by several external characteristics. Black-faced black spider monkeys typically have an all black pelage, and a black face color in contrast to the lighter red-faced Ateles paniscus . Additionally, Ateles chamek typically has shorter hairs on the prehensile tail and less exposed skin on the face than Ateles paniscus .

Ateles chamek and Ateles paniscus can also be distinguished by their different number of chromosomes (2n=34 and 2n=32 respectively). It is because of this difference, along with geographical isolation of the populations, that these two spider monkeys are now considered distinct species.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Like many other spider monkeys, black-faced black spider monkeys are polygyandrous and both males and females will attempt to reproduce with more than one mate during one reproductive cycle. Much of species-specific information on the mating system of Ateles chamek is not available due to the recent classification of Ateles chamek as its own species rather than as a subspecies of Ateles paniscus . Like other spider monkey species, it is possible male black-faced black spider monkeys may monopolize females in same social groups during mating attempts.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Black-faced black spider monkeys give birth throughout the year, however the majority of the births have been seen to occur in the fall months of September through December. They give birth to a single offspring after a long gestation period of 226 to 232 days. Much like other spider monkeys, black-faced black spider monkeys reach sexual maturity at the age of 4 to 5 years. In captivity, the interbirth time is on average 17.5 months, whereas in the wild it is likely longer, ranging between 28 and 30 months.

The sex ratio of offspring in black-faced black spider monkeys is female biased and driven by lower ranking female monkeys producing female offspring almost exclusively. Additionally, males tend to stay with their natal groups while female offspring disperse at the age of maturity to look for a mate. Male black-faced black spider monkeys also compete for mates, which does not impact the at birth sex ratio, but may impact amount of parental investment across the two sexes.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

Parental investment in Ateles chamek is largely the job of the mother. Male black-faced black spider monkeys participate only in the reproductive effort and do not invest in the offspring after insemination of the female. Young black-faced black spider monkeys spend the majority of the first 15 months of their lives living closely with and being carried by their mother (either clinging to their mother or riding on the mother’s back). The mother provides protection for the young and nutrients in the form of milk. By 15 months, the young can travel independently, but many remain in very close proximity of their mother until 23 months of age.

Lower ranking females produce female offspring almost exclusively, creating a sex-bias in the offspring overall. In contrast, higher-ranking females produce male and female offspring in equal numbers. This is likely due to a combination of reasons including the increased likelihood of female offspring to be successful in future matings due to male competition for mates rather than female competition. Also, the biased sex ratio and increased production of daughters over sons in lower-ranked females is likely because only sons of high-ranking females are likely to be reproductively successful, making the production of sons in lower-ranked females reproductively costly. In addition, maternal investment in offspring varies with the rank of the female. Higher-ranking females exhibit less bias in their maternal investment toward sons over daughters, but bias does occur. Evidence of this biased maternal investment can be seen in average gestation time of male and female offspring, as well as carrying time and weaning time. Higher-ranked females carry sons for a longer period of time (20 months for sons versus 17 months daughters), and tend to reject daughters attempts to nurse 4 months earlier than attempts of sons. Additionally, interbirth time between a son and subsequent birth of another offspring is longer (36 months) than the interbirth time between a daughter and subsequent birth (29 months) for a higher-ranked female. These biases are even more pronounced for lower-ranking females. When comparing the weaning time and carrying time for daughters of higher-ranked females to lower-ranked females there is little difference. Higher-ranked and lower-ranked females seem to invest similar amounts of parental investment in daughters regardless of rank. Post weaning parental investment of sons and daughters seems to be equal across the sexes, and also across the rank of the mother. Both sexes tend to stay close to their mother until approximately four years of age. At this point, which is also the offspring's point of sexual maturity, the females disperse to find mates in neighboring communities, and the males remain with their natal group and compete for mates.

• Parental Investment
• altricial altricial
• female parental care female parental care
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female
• extended period of juvenile learning
• maternal position in the dominance hierarchy affects status of young

Lifespan/Longevity

Limited species-specific data is available for the lifespan of Ateles chamek due to the recent classification as a species. Similar species of spider monkeys generally have a life span in the wild of longer than 20 years. The oldest black-faced black spider monkey in captivity lived for 48 years.

Behavior

Black-faced black spider monkeys are diurnal and are typically found in social groups with approximately 5 to 25 animals per square kilometer in hunted areas and up to 80 animals per square kilometer in non-hunted areas. Less individuals per square kilometer are usually present when there is competition with other species of primates. In addition to competition with other primate species as a factor determining population densities, food abundance tends to be the biggest predictor of abundance of black-faced black spider monkeys. Because of this, social parties are usually larger in the wet season than in the dry season. Average social group size tends to be approximately 3 individuals. Typically social interactions between groups tend to be peaceful, with males settling territory disputes should they arise. Party composition is usually stable with members of the party able to recognize each other. Social party membership does change when individuals leave or join the social group. Social grooming typically occurs between females and their offspring rather than between mates. Through observation, researchers have found Ateles chamek individuals spend approximately 30% of time feeding, 44% of time resting, and 25% of the time moving.

• Key Behaviors
• arboreal arboreal
• scansorial
• diurnal diurnal
• motile motile
• social social
• dominance hierarchies dominance hierarchies

Home Range

Black-faced black spider monkeys have a typical home range of 150 to 375 ha (1.5 square kilometers to 3.75 square kilometers) with larger ranges more typical when there are lesser numbers of primates in the surrounding areas. Males tend to travel throughout the territories while females and offspring tend to stay closer to a central area (approximately 27.5% of the total range area) within the territory. Habitat use and range also varies with fruit production. Typically entire social groups will move to areas of the range with the most abundance of food/resources.

Communication and Perception

Species-specific information about the communication patterns of Ateles chamek is limited, however, like other spider monkeys, black-faced black spider monkeys communicate vocally through grunts, howls, or screams. Additionally, mates may recognize each other through smell. Spider monkeys also shake tree branches, and signal each other by swinging their arms.

• Communication Channels
• visual visual
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• scent marks scent marks

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Black-faced black spider monkeys are predominantly frugivores, spending large amounts of time forging for fruits. They supplement their diets in times of low fruit availability with flowers, insects, and leaves, and will occasionally consume insects such as a caterpillars. Observations have shown black-faced black spider monkeys may be able to distinguish between the amounts of energy provided by different types of fruits and plants. Observed overconsumption (consuming more calories than what is likely required for daily activities) of food during periods of food abundance likely allows black-faced black spider monkeys to store excess energy in the form of fat. Then, during times of food shortage, they can use this fat reserve to perform daily functions.

Black-faced black spider monkeys are considered to be ripe-fruit specialists, and have been observed feeding largely on the figs of Fiscus boliviana and Ficus trigona . They substitute other fruits and leaves when figs are scare. Figs make up almost 50% of the diet and they spend considerable amounts of time daily foraging for figs. Daily time spent foraging for and consuming figs increases with increased abundance of the food source.

• Primary Diet
• herbivore herbivore
  • folivore folivore
  • frugivore frugivore

• Animal Foods
• insects

• Plant Foods
• leaves
• fruit
• flowers

Predation

Like Ateles paniscus and several other species of Ateles , Ateles chamek are large and are not easy prey for other similarly sized species. Despite the size of Ateles chamek , larger members of the family Felidae , such as jaguars, Panthera onca , do consume black-faced black spider monkeys.

In addition to natural predators, humans tend to be the largest threat for black-faced black spider monkeys. Humans in the surrounding areas hunt and consume black-faced black spider monkeys as food. Also, expansion of the agricultural industry and logging in Peru, Bolivia, and Brazil has increased the rate of habitat degradation. Replacement of the natural forests with agriculturally valued crops decreases the abundance of potential food sources for Ateles chamek . This process also creates larger open areas, making black-faced black spider monkeys an easier target for hunters.

Little is known about if or how Ateles chamek warn other social group members of potential predators.

Ecosystem Roles

Black-faced black spider monkeys disperse seeds of the plants that are common in black-faced black spider monkey diets. Although they tend to favor figs, they consume over 130 species of fruits, often ingesting the seeds and then dispersing them through defecation. The majority of the seeds eaten by black-faced black spider monkeys remain intact throughout this process. Seed distribution also occurs when they carry food for some distance before ingesting the fruits.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

Black-faced black spider monkeys provide a source of meat for hunters in areas surrounding the monkey populations. Because of the significant decrease in the population of Ateles chamek in recent years, several measures have been taken to limit the amount of hunting of this species of spider monkey.

• Positive Impacts
• food food

Economic Importance for Humans: Negative

There are no known adverse effects of Ateles chamek on humans.

Conservation Status

According to the IUCN Red List, Ateles chamek is currently listed as an endangered species. Because black-faced black spider monkeys reproduce infrequently, have only one offspring per reproduction, and have a long period of parental investment in young prior to the young’s reproductive maturity, it will likely be difficult for this population to increase in number. The additional human threats of hunting and deforestation make it even more likely that the number of Ateles chamek will continue to decline over time. Limitations or bans on hunting black-faced black spider monkeys in their natural habitat may improve the status of this species, but it may be unlikely that this effort will be substantial enough to help the species recover completely.

Additional Links

Encyclopedia of Life

Contributors

Sylvie Kademian (author), University of Michigan, Joanna Larson (editor), University of Michigan, Priscilla Tucker (editor), University of Michigan, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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Felton, A., A. Felton, J. Wood, et al.. 2009. Nutritional Ecology of Ateles chamek in lowland Bolivia: How Macronutrient Balancing Influences Food Choices. International Journal of Primatology , 30(5): 675-696.

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