Macaca nigraCelebes crested macaque

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Geographic Range

Macaca nigra is one of seven species of macaques endemic to the island of Sulawesi in Indonesia (Fooden 1969). Celebes crested macaques are restricted to northeast Sulawesi and the adjacent islands of Pulau Manadotua and Pulau Talise. They are no longer found on Pulai Lembeh. An introduced population of at least 100,000 individuals resides on Pulau Bacan, in the Maluku Islands (Supriatna and Andayani 2008). (Fooden, 1969; Supriatna and Andayani, 2008)

Habitat

Celebes crested macaques and tarsiers are the only non-human primates to inhabit the forests of Sulawesi (Riley 2010). Celebes crested macaques live in the island’s forests at moderate elevations ranging from 700 to 1100 m above sea level, most likely determined by fruit abundance (Rosenbaum et al. 1998b). These areas experience relatively constant temperatures, although there are fluctuations in rainfall between dry and wet seasons (Supriatna and Andayani 2008). They prefer humid, tropical lowland and upland rainforests, but they are also known to frequent agricultural areas that have increasingly encroached on their habitat (Rosenbaum et al. 1998b; O’Brien and Kinnaird 1997).

Celebes crested macaques live in many protected areas including Gunung Lokon, Gunung Amban, Tangkoko Batuangus, Dua Saudara, and Batu Putih, and are also commonly found in captivity (Supriatna and Andayani 2008). (O'Brien and Kinnaird, 1997; Riley, 2010; Rosenbaum, et al., 1998a; Supriatna and Andayani, 2008)

  • Range elevation
    700 to 1100 m
    2296.59 to 3608.92 ft

Physical Description

Celebes crested macaques are large, diurnal primates with black faces and bodies. Their crania are more prognathic and baboon-like than those of other macaques (Sugardjito et al. 1989), and their crown hairs form a crest, pointing backward and up. Celebes crested macaques also have prominent kidney-shaped ischial callosities, which are bright pink, and a “nubbin-like” tail (Groves 2001). Because their tails are short (about 20 mm long), they are commonly misidentified as apes (Cawthorn Lang 2006).

The face of Celebes crested macaques is black and thinly covered with hairs, and their body hair is dense, coarse, and woolly (Fooden 1969). Juvenile Celebes crested macaques are paler than adults, appearing more brown than black. Juveniles have black hairs where the crest will develop (Fooden 1969). As adult males age, their hair grays and becomes grizzled, most noticeably in the upper body; this occasionally occurs on the arms of younger males as well (Hamada et al. 1988).

Celebes crested macaques are sexually dimorphic, with males typically measuring from 520 to 570 mm and weighing 9.9 kg and females measuring from 445 to 570 mm and weighing 5.5 kg (Thierry et al. 2004). Adult females are also paler in color than adult males (Fooden 1969).

Among the species of macaques present on the island of Sulawesi, Celebes crested macaques are most difficult to distinguish from Gorontalo macaques, Macaca nigrescens. Both have black skin, but the upper half of the body of Celebes crested macaques is darker and more dull (Hamada et al. 1988). (Cawthon Lang, 2006; Fooden, 1969; Groves, 2001; Hamada, et al., 1988; Sugardjito, et al., 1989; Thierry, et al., 2004)

  • Sexual Dimorphism
  • male larger
  • Range mass
    5 to 18 kg
    11.01 to 39.65 lb
  • Average mass
    Males 9.9 kg; Females 5.5 kg
    lb
  • Range length
    445 to 570 mm
    17.52 to 22.44 in
  • Average length
    Males 520 to 570 mm; Females 445 to 570 mm
    in

Reproduction

Celebes crested macaques are promiscuous, or polygynandrous, as each individual (male and female) has multiple mates. Females exhibit sexual swelling in the anogenital area to indicate ovarian activity and sexual receptivity, sending visual and olfactory cues, which males sense by sniffing female genitalia (Engelhardt and Farajallah 2008). However, the degree to which males use visual, olfactory, and behavioral signs to determine female fertility remains unclear (Thierry et al. 2004).

Adult females approach high-ranking males for sex more often than they do low-ranking males, although all males copulate about the same amount (Reed et al. 1997). A female presents herself to a male by facing her swollen genitals, slightly raised, toward the male, and smacking her lips. The male holds the female’s legs and waist during copulation. The pair engages in reciprocal grooming following intercourse (Nickelson and Lockard 1978). There are two types of ejaculatory patterns among species of macaques. Male Celebes crested macaques mount the female multiple times but only ejaculate during the last mount (multiple-mount ejaculation) (Caldecott 1986).

Sexual swelling of the female anogenital area also occurs when females are not ovulating, which promotes non-procreative copulation (Thomson et al. 1992). Homosexual behavior such as displaying, mounting, and genetal contact has also been observed among males of this species (Soltis 2004). (Caldecott, 1986; Engelhardt and Farajallah, 2008; Nickelson and Lockard, 1978; Reed, et al., 1997; Soltis, 2004; Thierry, et al., 2004; Thomson, et al., 1992)

Little is known about the reproductive biology of Celebes crested macaques in the wild (Engelhardt and Farajallah 2008). They breed year-round, although periods of high ovarian activity among adult females occur from August to June, and birthing peaks between January and May (Engelhardt and Farajallah 2008).

Fertility of males and females overlaps (Bernstein et al. 1982). Females have a menstrual cycle of approximately 32 days, which is unusually long for macaques and occurs because of an extended follicular phase. Cycle length and maximal genital swelling period are extended when males are absent (Bernstein et al. 1982; Thomson et al. 1992).

Females give birth to a single offspring every 18 months. Gestation last 5.5 months. Offspring spend much less time with their mother at 4 months of age and are completely weaned by 1 year of age (Durrell Wildlife Conservation Trust 2011).

In most populations, the adult sex ratio is 3 females to 5 males (Thierry et al., 2004). Macaques are sexual bimaturists, with females reaching physical maturity faster than males, though the hormonal processes responsible for maturation are identical in both sexes (Thierry, 2007). Males produce sperm around 3 or 4 years of age, though they do not reach a body mass necessary for mating (physical maturity) for another 3 to 6 years (Thierry et al. 2004; Howard et al. 1999). (Bernstein, et al., 1982; "Sulawesi crested black macaque", 2011; Engelhardt and Farajallah, 2008; Howard, et al., 1999; Thierry, et al., 2004; Thomson, et al., 1992)

  • Breeding interval
    Celebes crested macaques typically give birth once every 18 months.
  • Breeding season
    Celebes crested macaques breed year-round, although breeding increases between August and June.
  • Average number of offspring
    1
  • Average number of offspring
    1
    AnAge
  • Range gestation period
    5 to 6 months
  • Average weaning age
    12 months
  • Range age at sexual or reproductive maturity (female)
    4 to 6 years
  • Range age at sexual or reproductive maturity (male)
    4 to 6 years

Little is known regarding parental care among Celebes crested macaques. Based on comparable patterns of behavior and social structure, parental investment in this species is likely similiar to that of other macaques: care is primarily maternal, though aunting behavior occurs, in which an infant is carried by juvenile females supervised by the mother (Cawthorn Lang 2006). Infants of this speices often cling to their mother's belly for protection (Durrell Wildlife Conservation Trust 2011).

Although sexual swelling in the anogenital area marks periods of ovulation, sexual swelling also occurs when females are not ovulating, promoting non-procreative copulation (Thomson et al. 1992). This may confuse paternity, increasing male parental care and decreasing the likelihood of infanticide (Soltis 2004). (Cawthon Lang, 2006; "Sulawesi crested black macaque", 2011; Soltis, 2004; Thomson, et al., 1992)

  • Parental Investment
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

The average life span of Celebes crested macaques is 18 years Cawthorn Lang 2006). The oldest individual in captivity survived 34 years (Schulz 2009). (Cawthon Lang, 2006; Schulz, 2009)

  • Range lifespan
    Status: captivity
    34 (high) years
  • Average lifespan
    Status: wild
    18 years
  • Average lifespan
    Status: captivity
    34 years
    AnAge

Behavior

Celebes crested macaques live in groups of 50 to 97 individuals, which is unusually large for the genus (O’Brien and Kinnaird 1997). Groups generally include more females than males (Reed et al. 1997). Females remain within the group into which they were born, while males disperse to unrelated groups when they reach sexual maturity (Thierry 2007; Rosenbaum et al. 1998b; Sugardjito et al. 1989). Females have an egalitarian social structure, whereas males form a linear and transitive dominance hierarchy (Reed et al. 1997). Groups are generally tolerant, characterized by appeasement displays, minimal aggression (biting each other), and “symmetry in conflict” (Baker and Estep 1985; Bernstein and Baker 1988).

Male macaques exhibit a variety of signals to indicate aggression: staring with an open mouth, grinning with the mouth closed, yawning, lunging, and chasing (Nickelson and Lockard 1978; Reed et al. 1997). Submission and satisfaction are signaled with a grimace and lip smacking (Nickelson and Lockard 1978).

Celebes crested macaques are diurnal and spend 59% of their waking hours foraging, feeding, and moving. They are primarily terrestrial, traveling an average of 2.4 km per day, though time spent on the ground and distance traveled per day changes in primary forest, where fruit is abundant and does not require as much travel (O’Brien and Kinnaird 1997; Rosenbaum et al. 1998b). Celebes crested macaques generally socialize in the morning, rest in the afternoon, and sleep in trees (O’Brien and Kinnaird 1997). (Baker and Estep, 1985; Bernstein and Baker, 1988; Nickelson and Lockard, 1978; O'Brien and Kinnaird, 1997; Reed, et al., 1997; Rosenbaum, et al., 1998a; Sugardjito, et al., 1989; Thierry, 2007)

  • Range territory size
    0.47 to 3.48 km^2

Home Range

The mean home range of Celebes crested macaques is 216 ha. Territories range from 0.47 to 3.48 sq km. However, macaques that feed on fruit stay closer to their home range, as less travel is necessary while foraging (O’Brien and Kinnaird 1997).

Groups are unusually large, ranging from 50 to 97 individuals (O'Brien and Kinnaird 1997). The average population density of Celebes crested macaques is 3 individuals per sq km, although in Tangkoko Batuangus, population density reaches as many as 60 individuals per sq km (Supriatna and Andayani 2008). In some cases, population density is correlated with density of fig trees (Hamada et al. 1994). (Hamada, et al., 1994; O'Brien and Kinnaird, 1997; Supriatna and Andayani, 2008)

Communication and Perception

Celebes crested macaques utilize a variety of visual and physical behaviors to communicate. To indicate aggression, males stare with an open mouth, grin with the mouth closed, yawn, lunge, and chase (Nickelson and Lockard 1978; Reed et al. 1997). Submission and satisfaction are signaled with a grimace and lip smacking (Nickelson and Lockard 1978). As with other macaques, males are known to silently bare their teeth, postulated as a display of “peaceful intentions” (Thierry et al. 2000). Dominant males also bare their canines in a “yawn” to indicate supremacy (Assahad et al. 2008).

Celebes crested macaques also use vocalizations. They are known for a loud, bird-like call that may be a method of intervening in conflicts, signaling to keep away from other groups (Muroyama and Thierry 1998; Kinnaird and O’Brien 1999), or as a “signal of dominance to prevent contests between males for mates” (Neumann et al. 2010). Frequency and complexity of calls correlates with male rank, with high-ranking males emitting complex calls more frequently than subordinates (Assahad et al. 2008). (Assahad, et al., 2008; Kinnaird and O'Brien, 1999; Muroyama and Thierry, 1998; Neumann, et al., 2010; Nickelson and Lockard, 1978; Reed, et al., 1997; Thierry, et al., 2000)

Food Habits

Celebes crested macaques are mostly frugivorous, and figs comprise the majority of their diet. However, they have a diverse diet, consuming more than 145 species of plants, mostly fruit (Dracontomelon spp. and Ficus spp.), as well as some invertebrates (O’Brien and Kinnaird 1997; Rosenbaum et al. 1998b; Riley 2007). When fruit is scarce, their diet is supplemented by insects, shoots, young leaves, and the stems of flowering plants (Riley 2007; Supriatna and Andayani 2008). Celebes crested macaques have been observed preying on fruit bats, forest geckos, frogs, and the eggs of the red junglefowl and black-naped monarch flycatcher (O’Brien and Kinnaird 1997). Members of this species also raid crops, including maize (Zea mays), yams (Dioscorea), cassava (Manihot esculenta), papayas (Carica papaya), bananas (Musa), and cacao (Theobroma cacao) (Bynum et al. 1999; Rosenbaum et al. 1998a; Riley, 2007).

Celebes crested macaques forage throughout the day, occasionally storing food reserves in their cheek pouches (Schulz 2009). (Bynum, et al., 1999; O'Brien and Kinnaird, 1997; Riley, 2007; Rosenbaum, et al., 1998b; Rosenbaum, et al., 1998a; Schulz, 2009; Supriatna and Andayani, 2008)

  • Animal Foods
  • mammals
  • amphibians
  • reptiles
  • eggs
  • insects
  • terrestrial non-insect arthropods
  • terrestrial worms
  • Plant Foods
  • leaves
  • wood, bark, or stems
  • seeds, grains, and nuts
  • fruit
  • flowers

Predation

Celebes crested macaques have no major predators. They are, however, hunted by humans for their meat (Riley 2007; Durrell Wildlife Conservation Trust 2011). ("Sulawesi crested black macaque", 2011; Riley, 2007)

Ecosystem Roles

Celebes crested macaques have no major predators or catarrhine competitors (Riley 2007). Many macaques on the island of Sulawesi are known to associate with birds, including hair-crested drongos and yellow-billed malkoha (Matsumura 2001; Whitten et al. 2002). These birds prey on the insects that leave the canopy when macaques pass through (Matsumura 2001).

As frugivores, Celebes crested macaques act as seed dispersers of rainforst trees, especially for species of Dracomelon and Ficus (Rosenbaum et al. 1998b).

Fecal tests of Celebes crested macaques revealed the presence of parasites including Balantidium sp., Entamoeba sp., Ascaris sp., and Trichostrongylus sp., all of which are found in both humans and nonhuman primates (Paulsen et al. 2006). Among captive Celebes crested macaques, 72.2% (13 out of a sample of 18 individuals) were parasitized, with a mean of 1.1 parasite taxon per individual (Jones-Engel et el. 2004). A study of Sulawesi macaques kept as pets, which included Celebes crested macaques, found 7 taxa of intestinal protozoa (Blastocystis hominis, Iodamoeba butschlii, Entamoeba coli, Entamoeba hartmanni, Chilomastrix mesnili, Endolimax nana, and Retortamonas intestinalis) and 3 taxa of nematodes (hookworm, Trichuris sp., and Ascaris sp.) (Jones-Engel et al. 2004). (Jones-Engel, et al., 2004; Matsumura, 2001; Paulsen, et al., 2006; Rosenbaum, et al., 1998a; Whitten, et al., 2002)

  • Ecosystem Impact
  • disperses seeds
Mutualist Species
Commensal/Parasitic Species
  • Balantidium sp.
  • Blastocystis hominis
  • Iodamoeba butschlii
  • Entamoeba coli
  • Entamoeba hartmanni
  • Chilomastrix mesnili
  • Endolimax nana
  • Retortamonas intestinalis
  • hookworm Necator americanus
  • Trichuris sp.
  • Ascaris sp.

Economic Importance for Humans: Positive

Celebes crested macaques play an important role in local folklore, and can serve as household pets (Hamada et al. 1988; Riley and Priston 2010). Considered a delicacy, they are hunted for bush meat and are served on holidays and special occasions (Schulz 2009; Durrell Wildlife Conservation Trust 2011). CITES prohibits live trade of this speices, though illegal trafficking may still occur (Supriatna and Andayani 2008).

Because Celebes crested macaques are the only non-human primate model for Type II diabetes mellitus, they are valuable in scientific research (Thomson et al. 1992).

This species also plays a considerable role in ecotourism (Schulz 2009). (Hamada, et al., 1988; Riley and Priston, 2010; Schulz, 2009; Supriatna and Andayani, 2008; Thomson, et al., 1992)

Economic Importance for Humans: Negative

As humans reduce habitat, cut down fig trees, which are a key component to the diet of macaques, and as farms expand into forests, macaques have adapted to include crops in their diet, exploiting human resources (Richard et al. 1989; Riley and Priston 2010). Although local folklore describes humans and macaques as intertwined, crop raiding has earned them reputations as “pests” and “weed species” (Richard et al. 1989). Crop raiding is common among all species of macaques, including Celebes crested macaques (Riley and Priston 2010).

Certain diseases can also be transmitted among humans and macaques (Jones-Engel et al., 2005; Riley, 2010). There is evidence of macaque exposure to human respiratory viruses, including influenza A and parainfluenza 1, 2, and 3. This anthropozoonotic exchange may occur through individuals kept as pets, which come into contact with both wild macaques and humans (Jones-Engel et al. 2005). (Jones-Engel, et al., 2005; Richard, et al., 1989; Riley and Priston, 2010; Riley, 2007; Riley, 2010)

Conservation Status

In 2008, the IUCN listed Celebes crested macaques as critically endangered (Supriatna and Andayani 2008). This species is also listed in CITES Appendix II. Population size has decreased by 80% in the last 40 years, primarily due to hunting and loss of habitat (Kyes et al. 2000; Laatung et al. 2006). There are estimated to be 4,000 to 6,000 individuals in the wild. On Bacan Island, there is an introduced population of 100,000 individuals, which is not included in the population estimate (Hamada et al. 1994), but could become the last surviving population of Celebes crested macaques in the near future (Riley 2010).

Main threats to the conservation of Celebes crested macaques include human population growth and land conversion (Bynum et al. 1999). Following recent spikes in human habitation, which in 2002 was 132 individuals per sq km, is large-scale deforestation by logging, the transmigration program, and cash crop farming, most of which is partially funded by the government (Whitten et al. 2002).

Humans cut down trees that are important to the diet and habitat of macaques, such as fig trees (Riley and Priston 2010). Human-macaque sharing of resources is occasionally possible, as with Arenga pinnata palm trees, from which macaques gather fruit and humans take palm fronds. However, deforestation for timber and firewood and clearing for agriculture permanently removes resources utilized by macaques (Riley, 2010).

Despite their critical conservation condition, the total area of protected land inhabited by Celebes crested macaques (16,848 ha) is less than any other macaques on the island of Sulawesi (Riley 2010). (Bynum, et al., 1999; Hamada, et al., 1994; Kyes, et al., 2000; Laatung, et al., 2006; Riley, 2010; Supriatna and Andayani, 2008; Whitten, et al., 2002)

Other Comments

Celebes crested macaques, Macaca nigra (synonyms: Macaca lembicus, Macaca malayanus), are also known as black crested macaques, crested black macaques, Sulawesi black macaquse, Sulawesi macaques, and incorrectly as Celebes black apes (Supriatna and Andayani 2008; Riley 2010). Hybrids of M. nigra and M. nigriscens have been recorded (Sugardjito et al. 1989). (Riley, 2010; Sugardjito, et al., 1989; Supriatna and Andayani, 2008)

Contributors

Rae Ellen Bichell (author), Yale University, Eric Sargis (editor), Yale University, Gail McCormick (editor), Animal Diversity Web Staff.

Glossary

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

diurnal
  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

food

A substance that provides both nutrients and energy to a living thing.

frugivore

an animal that mainly eats fruit

herbivore

An animal that eats mainly plants or parts of plants.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

island endemic

animals that live only on an island or set of islands.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nomadic

generally wanders from place to place, usually within a well-defined range.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year

References

Durrell Wildlife Conservation Trust. 2011. "Sulawesi crested black macaque" (On-line). Durrell Wildlife Conservation Trust. Accessed April 26, 2011 at http://www.durrell.org/Animals/Mammals/Sulawesi-crested-black-macaque/.

Assahad, G., C. Neumann, K. Hammerschmidt, D. Perwitasari-Farajallah, A. Engelhardt. 2008. Rank-dependent differences in loud call frequency and structure in Sulawesi Crested Black Macaques (Macaca nigra). Folia Primatologica, 79: 311.

Baker, S., D. Estep. 1985. Kinship and affiliative behavior patterns in a captive group of Celebes black apes (Macaca nigra). Journal of Comparative Psychology, 99: 356-360.

Bernstein, I., S. Baker. 1988. Activity patterns in a captive group of Celebes black apes (Macaca nigra). Folia Primatologica, 51: 61-75.

Bernstein, I., K. Bruce, L. Williams. 1982. The Influence of Male Presence or Absence on the Reproductive Cycle of Celebes Black Ape Females (Macaca nigra). Primates, 23(4): 587-591.

Bynum, E., A. Kohlhaas, A. Pramono. 1999. Conservation status of Sulawesi macaques. Tropical Biodiversity, 6: 123-144.

Caldecott, J. 1986. Mating patterns, societies and the ecogeography of macaques. Animal Behavior, 34: 208-220.

Cawthon Lang, K. 2006. "Primate Factsheets: Crested black macaque (Macaca nigra) Taxonomy, Morphology, & Ecology" (On-line). Accessed April 23, 2011 at http://pin.primate.wisc.edu/factsheets/entry/crested_black_macaque.

Engelhardt, A., D. Farajallah. 2008. Reproductive biology of Sulawesi crested black macaques (Macaca nigra). Folia Primatologica, 79: 326.

Fooden, J. 1969. Taxonomy and Evolution of the Monkeys of Celebes. Basel, Switzerland: S. Karger.

Groves, C. 2001. Primate Taxonomy. Washington, D.C.: Smithsonian Inst Pr.

Hamada, Y., T. Oi, T. Watanabe. 1994. Macaca nigra on Bacan Island, Indonesia: its morphology, distribution and present habitat. International Journal of Primatology, 15(3): 487-493.

Hamada, Y., T. Watanabe, O. Takenaka, B. Suryobroto, Y. Kawamoto. 1988. Morphological Studies on the Sulawesi Macaques. Primates, 29(1): 65-80.

Howard, C., T. Fang, C. Southwick, J. Erwin, J. Sugardjito, J. Supriatna, A. Kohlhaas, N. Lerche. 1999. Islet Cell Antibodies in Sulawesi Macaques. American Journal of Primatology, 47(3): 223-229.

Jones-Engel, L., G. Engel, M. Schillaci, K. Kyes, J. Froehlich, U. Paputungan, R. Kyes. 2004. Prevalence of Enteric Parasites in Pet Macaques in Sulawesi, Indonesia. American Journal of Primatology, 62(2): 71-82.

Jones-Engel, L., M. Schillaci, G. Engel, U. Paputungan, J. Froehlich. 2005. Characterizing primate pet ownership in Sulawesi: implications for disease transmission. Pp. 196-221 in J Paterson, J Wallis, eds. Commensalism and conflict: the human-primate interface. Norman, OK: American Society of Primatologists.

Kinnaird, M., T. O'Brien. 1999. A contextual analysis of the loud call of the Sulawesi black macaque, Macaca nigra. Tropical Biodiversity, 6: 37-42.

Kyes, R., E. Iskander, U. Paputungan. 2000. Population survey of the Sulawesi black macaque at Tangkoko Nature Reserve. American Journal of Primatology, 51: 68.

Laatung, S., R. Kyes, A. Mardiastuti, J. Onibala. 2006. Population survey of the Sulawesi black macaques at the Duasaudara Nature Reserve, North Sulawesi, Indonesia. American Journal of Primatology, 68: 62-63.

Matsumura, S. 2001. Yellow-billed malhokas (Phaenicophaeus calyorhynchus) following moor macaques (Macaca maurus) in South Sulawesi, Indonesia. Journal of Tropical Ecology, 17: 619-623.

Muroyama, Y., B. Thierry. 1998. Species differences of male loud calls and their perception in Sulawesi macaques. Primates, 39: 115-126.

Neumann, C., G. Assahad, K. Hammerschmidt, D. Perwitasari-Parajallah, A. Engelhardt. 2010. Loud calls in male crested macaques, Macaca nigra: a signal of dominance in a tolerant species. Animal Behaviour, 79(1): 187-193.

Nickelson, S., J. Lockard. 1978. Ethogram of Celebes Monkeys (Macaca nigra) in Two Captive Habitats. Primates, 19(3): 437-447.

O'Brien, T., M. Kinnaird. 1997. Behavior, diet, and movements of the Sulawesi crested black macaque. International Journal of Primatology, 18: 321-351.

Paulsen, D., R. Kyes, E. Sulistiawati, L. Rosmanah, J. Onibala, E. Iskander, S. Kelley. 2006. Survey of intestinal parasites in a population of Sulawesi black macaques at the Tangkoko Nature Reserve, North Sulawesi, Indonesia. American Journal of Primatology, 68(S1): 109.

Reed, C., T. O'Brien, M. Kinnaird. 1997. Male social behavior and dominance in the Sulawesi crested black macaque (Macaca nigra). International Journal of Primatology, 18: 247-260.

Richard, A., S. Goldstein, R. Dewar. 1989. Weed macaques: evolutionary implications of macaque feeding ecology. International Journal of Primatology, 10: 569-594.

Riley, E. 2010. The endemic seven: Four decades of research on the Sulawesi macaques. Evolutionary Anthropology, 19(1): 22-36.

Riley, E. 2007. The human-macaque interface: conservation implications of current and future overlap and conflict in Lore Lindu National Park, Sulawesi, Indonesia. American Anthropology, 109: 473-484.

Riley, E., N. Priston. 2010. Macaques in farms and folklore: exploring the human-nonhuman primate interface in Sulawesi, Indonesia. American Journal of Primatology, 71: 1-7.

Rosenbaum, B., T. O'Brien, M. Kinnaird, J. Supriatna. 1998. Population densities of Sulawesi crested black macaques (Macaca nigra) on Bacan and Sulawesi, Indonesia: effects of habitat disturbance and hunting. American Journal of Primatology, 44: 89-106.

Rosenbaum, B., C. Southwick, J. Supriatna, Y. Muskita, A. Yunuar, R. Sinaga, R. Sapulette. 1998. A survey of population and habitat of the Sulawesi crested-black macaque (Macaca nigra) on Bacan Island, Maluku, Indonesia. Tropical Biodiversity, 5(2): 139-154.

Schulz, K. 2009. "Macaca nigra (Desmarest, 1822)" (On-line). Encyclopedia of Life. Accessed April 26, 2011 at http://www.eol.org/pages/323954.

Soltis, J. 2004. Mating Systems. Pp. 135-154 in B Thierry, M Singh, W Kaumanns, eds. Macaque societies: a model for the study of social organization. Cambridge: Cambridge University Press.

Sugardjito, J., C. Southwick, J. Supriatna, A. Kohlaas, S. Baker, J. Erwin, J. Froehlich, N. Lerche. 1989. Population survey of macaques in northern Sulawesi. American Journal of Primatology, 18(4): 285-301.

Supriatna, J., N. Andayani. 2008. "Macaca nigra" (On-line). In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. Accessed April 10, 2011 at http://www.iucnredlist.org/apps/redlist/details/12556/0.

Thierry, B. 2007. Unity in diversity: lessons from macaque societies. Evol Anthropol, 16: 224-238.

Thierry, B., E. Bynum, S. Baker, M. Kinnaird, S. Matsumura, Y. Muroyama, T. O'Brien, O. Petit, K. Watanabe. 2000. The social repertoire of Sulawesi macaques. Primate Research, 16: 203-226.

Thierry, B., M. Singh, W. Kaumanns. 2004. Macaque Societies. Cambridge: Cambridge University Press.

Thomson, J., D. Hess, K. Dahl, S. Iliff-Sizemore, R. Stouffer, D. Wolf. 1992. The Sulawesi Crested Black Macaque (Macaca nigra) Menstrual Cycle: Changes in Perineal Tumescence and Serum Estradiol, Progesterone, Follicle-Stimulating Hormone, and Luteinizing Hormone Levels. Biology of Reproduction, 46: 879-884.

Whitten, T., G. Henderson, M. Mustafa. 2002. The Ecology of Sulawesi. Jakarta: Periplus.