COMMON LONG-TAILED MACAQUE

Macaca fascicularis

Geographic Distribution and Habitat
Common long-tailed macaques, also called crab-eating macaques and cynomolgus monkeys, are widely distributed across southeast Asia, including in Bangladesh,  Brunei Darussalam, Cambodia, India (Nicobar Island), large areas of Indonesia, Lao PDR, Malaysia, Myanmar, the Philippines, Singapore, Thailand, Timor-Leste, and Viet Nam. This species inhabits a diverse range of habitats including coastal forests, mixed mangrove swamps, freshwater swamps, scrub grasslands, evergreen forests, bamboo forests, deciduous forests, and human settlements. It has also been introduced by humans to several areas outside of its native range, including China and the island of Mauritius. There is a zone of hybridization between the common long-tailed macaque and the rhesus macaque (Macaca mulata) in mainland southeast Asia, which makes it hard to determine the northern boundary of this species.

TAXONOMIC NOTES

There are at least 10 subspecies of the common long-tailed macaque: the dark-crowned long-tailed macaque, Macaca fascicularis atriceps, the Burmese long-tailed macaque, M. fascicularis aureus, the Con Song long-tailed macaque, M. fascicularis condorensis, the long-tailed macaque, M. fascicularis fascicularis, the Simeulue long-tailed macaque, M. fascicularis fusca, the Karimunjawa long-tailed macaque, M. fascicularis karimondjawae, the Lasia long-tailed macaque, M. fascicularis lasiae, the Philippine long-tailed macaque, M. fascicularis philippensis, the Maratua long-tailed macaque, M. fascicularis tua, and the Nicobar long-tailed macaque, M. fascicularis umbrosus. Most of these sub-species’ populations are isolated and display few apparent differences apart from variations in pelage color, tail length, and cheek whiskers. 

Common long-tailed macaque geographic range. Map: IUCN, 2020

Size, Weight, and Lifespan
Common long-tailed macaques were named for their remarkably long tails, which aid their balance and are longer than their head and body length, typically measuring around 19–23.5 in (50–60 cm). Their head and body length measures about 15–18.5 in (40–47 cm). These macaques show sexual dimorphism in size; males weigh approximately 10.5–15.5 lbs (4.8–7 kg), whereas females weigh approximately 6.5–8.5 lbs (3–4 kg).

Long-tailed macaques have an average lifespan of 15–30 years, with longer lifespans documented in captivity.

Appearance
Common long-tailed macaques have a pelage that ranges from gray to brown and is lighter at their bellies. At birth, infants have a much darker pelage, which gradually becomes lighter as they mature. Their faces are pink with yellow-brown eyes and large, square ears. Males are distinguished by their unique mustache, whereas females have a beard. Both sexes have cheek whiskers. These monkeys also have cheek pouches, which allows them to store food for later consumption.

Crab-eating or long-tailed macaque (Macaca fascicularis) in the beautiful Erawan National Park, Kanchanaburi, Thailand.

What Does It Mean?

Frugivorous:
Having a diet that consists of fruits.

Infanticide:
The killing of young offspring by a mature animal of the same species.

Mate guarding:
The physical guarding of a female in order to deny rival males the opportunity to mate with her.

Sexual dimorphism:
Distinct difference in size or appearance between the sexes of an animal in addition to difference between the reproductive organs themselves.

Subspecies:
A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

Visit the Glossary for more definitions

Diet
Common long-tailed macaques have a natural diet that consists of fruits, flowers, young leaves, and invertebrates. They are primarily frugivorous; they prefer to eat fruit but eat other items when fruit is not available. However, these monkeys are often found in close proximity to human populations and therefore the diet of different groups can vary depending on human provisioning or access to human refuse sites.

They also displays some feeding behaviors rarely seen in primates. Common long-tailed macaques at two different sites in Indonesia have been observed catching and eating fish. They have also been observed using stones as tools to break into oysters and crabs and access the edible parts. Indeed, this species is sometimes referred to as the “crab-eating macaque” due to observations of coastal-living groups eating small crabs.

Unlike some other primates, this species does not usually swallow larger seeds from fruit. Their cheek pouches allow them to quickly take fruit from a tree, and then they chew fruits one by one and spit out the seeds while keeping the other fruits in their cheek pouches.

Behavior and Lifestyle
Since this species is so widespread, their behaviors and lifestyles vary across their range, from urban to wild environments. However, groups of common long-tailed macaques in different habitats all spend high proportions of their day moving (around 18–30%), feeding (16–24%), and resting (16–20%). They also spend a lot of time engaged in social activities, such as grooming, play, and sexual behaviors, although time spent monitoring humans can decrease the amount of time they spend in social interactions in areas of their habitat that are impacted by humans.

They are primarily arboreal species, spending most of their time in trees, but will also travel on the ground. Their ranges can overlap with other primate species, and they are known to have agonistic encounters with other species, such as silvered leaf monkeys.

Daily Life and Group Dynamics 
Common long-tailed macaques live in groups ranging in size from around 20 to over 100 individuals. Groups contain multiple adult males and females, though there are usually more adult females than males. Females remain in their natal groups and the hierarchy is based around matrilines (groups of highly related females). Males migrate into new groups when they reach sexual maturity and then throughout their lives. Younger males tend to migrate with group mates and may attempt to take over a new group at the top of the dominance hierarchy. Older males tend to migrate alone and “unobtrusively” enter the new group at a lower position in the hierarchy.

There are often within-group conflicts, but these macaques also show reconciliation after a conflict. Directly after a conflict, the aggressor or victim will often approach their opponent and display an affiliative behavior, which likely helps to reduce stress and further conflict after a fight.

Fun Facts

There are at least ten sub-species of  long-tailed macaques.

These monkeys use stone tools to break into oysters and crabs, which may be a cultural behavior.

After conflicts between individuals, the victim and aggressor often engage in reconciliation.

Communication
Like many other primates, long-tailed macaques communicate using a range of behaviors, such as vocalizations, facial expressions, and gestures. They produce a wide range of vocalizations including barks, grunts, screams, and contact calls, among many others. These are used in a number of contexts including affiliative and agonistic interactions, during copulation, or in response to threats. Facial expressions and gestures such as baring their teeth, lip smacking, or genital presenting are also used in social interactions, often to signal appeasement.

Reproduction and Family
The males at the top of the hierarchy are able to monopolize the females and thus reproduce more than lower-ranking males. They do this in part through “mate guarding,” which involves staying very close to a female and preventing other males from mating with her while she is fertile. Males recognize when a female is fertile through differences in her behavior, such as the female initiating copulation.

After a gestation period of around 163 days, the female will give birth to a single infant. Infanticide by adult males sometimes occurs in this species. This is beneficial to the male because the female becomes fertile again earlier and the male has a chance to reproduce more quickly. Males and females reach sexual maturity at around 4–5 years of age.

Ecological Role
Primates often aid in seed dispersal through consuming seeds and then dispersing them via their faeces. However, these macaques do not ingest many seeds, instead spitting them out. Nonetheless, their cheek pouches mean that, although they do not ingest these seeds, they can still carry them some distance from the plant before spitting them out and therefore play a role in seed dispersal.

Conservation Status and Threats
The common long-tailed macaque is currently classified as Vulnerable by the International Union for Conservation of Nature (IUCN, 2015) and the overall population is thought to be decreasing. It is thought that this species has declined by over 30% throughout its range in the last 36–39 years. Although they are widely distributed, excessive hunting and persecution due to negative interactions with humans contribute to their “vulnerable” status.

Major threats include hunting for food, sport, and use in research. They are also threatened by increasing human-macaque interaction due to increasing human development. These interactions can lead to human-wildlife conflict, as well as other threats such as traffic collisions or attacks by domestic dogs. It has also been found that human presence can push these macaques away from foraging sites at the coast and therefore disrupt their tool use behaviors, which are viewed as a cultural tradition in these monkeys. Scientists estimate that there will be a further 30% reduction in the population over the next 36–39 years.

​​Conservation Efforts
​The common long-tailed macaque is included in Appendix II of the Convention on International Trade in Endangered Species (CITES). It is also listed on wildlife protection acts in India and Bangladesh. However, there are few specific conservation efforts in place throughout its range, likely because it is still viewed as an “abundant” species. In particular, more research is needed on the various sub-species.

References:

  • ​Corlett, R. T., & Lucas, P. W. (1990). Alternative seed-handling strategies in primates: seed-spitting by long-tailed macaques (Macaca fascicularis). Oecologia82(2), 166-171.
  • Girard-Buttoz, C., Heistermann, M., Rahmi, E., Marzec, A., Agil, M., Fauzan, P. A., & Engelhardt, A. (2014). Mate-guarding constrains feeding activity but not energetic status of wild male long-tailed macaques (Macaca fascicularis). Behavioral ecology and sociobiology68(4), 583-595.
  • Hambali, K., Ismail, A., & Md-Zain, B. M. (2012). Daily activity budget of long-tailed macaques (Macaca fascicularis) in Kuala Selangor Nature Park. International Journal of Basic & Applied Sciences12, 47-52.
  • Malaivijitnond, S., Lekprayoon, C., Tandavanittj, N., Panha, S., Cheewatham, C., & Hamada, Y. (2007). Stone‐tool usage by Thai long‐tailed macaques (Macaca fascicularis). American Journal of Primatology: Official Journal of the American Society of Primatologists69(2), 227-233.
  • Marty, P. R., Beisner, B., Kaburu, S. S., Balasubramaniam, K., Bliss-Moreau, E., Ruppert, N., … & McCowan, B. (2019). Time constraints imposed by anthropogenic environments alter social behaviour in longtailed macaques. Animal behaviour150, 157-165.
  • Van Noordwijk, M. A., & Van Schaik, C. P. (1985). Male migration and rank acquisition in wild long-tailed macaques (Macaca fascicularis). Animal Behaviour33(3), 849-861.
  • Rodman, P. S. (1991). Structural differentiation of microhabitats of sympatric macaca fascicularis and M. nemestrina in East Kalimantan, Indonesia. International Journal of Primatology12(4), 357-375.
  • Sha, J. C. M., Gumert, M. D., Lee, B. P. H., Fuentes, A., Rajathurai, S., Chan, S., & Jones-Engel, L. (2009). Status of the long-tailed macaque Macaca fascicularis in Singapore and implications for management. Biodiversity and Conservation18(11), 2909-2926.
  • Sha, J. C. M., & Hanya, G. (2013). Diet, activity, habitat use, and ranging of two neighboring groups of food‐enhanced long‐tailed macaques (Macaca fascicularis). American Journal of Primatology75(6), 581-592.
  • Stewart, A. M. E., Gordon, C. H., Wich, S. A., Schroor, P., & Meijaard, E. (2008). Fishing in Macaca fascicularis: a rarely observed innovative behavior. International Journal of Primatology29(2), 543-548.
  • Yeager, C. P. (1996). Feeding ecology of the long-tailed macaque (Macaca fascicularis) in Kalimantan Tengah, Indonesia. International Journal of Primatology17(1), 51-62.
  • ​Alltheworldsprimates.org
  • https://www.iucnredlist.org/species/12551/17949449#

Written by Jennifer Botting, PhD, July 2020