Here’s a complete and richly detailed overview of the Crab-eating Macaque (Macaca fascicularis), one of Southeast Asia’s most widespread and ecologically adaptable primates:

🐒 **Crab-eating Macaque (Macaca fascicularis)**

Common Names

Crab-eating macaque
Long-tailed macaque
Cynomolgus monkey
Indonesian: Monyet ekor panjang
Thai: Ling sam ling
Malay: Kera ekor panjang

Taxonomy & Classification

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Cercopithecidae (Old World monkeys)
Genus: Macaca
Species: M. fascicularis
Scientific name meaning:
“Fascicularis” means “bundled” or “banded,” likely referring to the macaque’s coat pattern or social grouping behavior.

Description & Identification

Size:
- Males: 40–65 cm body length, tail 50–70 cm, weight 5–9 kg.
- Females: 38–55 cm body length, tail 40–65 cm, weight 3–6 kg.
Body: Slender and agile, built for climbing and swimming.
Tail: Exceptionally long — almost equal to or longer than body length, hence the name long-tailed macaque.
Coloration:
- Fur ranges from grayish-brown to golden olive on the back, lighter on the underside.
- Face is pinkish or gray, often with a ridge of hair forming a crown or whiskered appearance.
Facial features: Expressive eyes, flat nose, and bare muzzle typical of Old World monkeys.

Distribution

Native range: Widespread throughout Southeast Asia, including:
- Thailand, Cambodia, Laos, Vietnam, Myanmar, Malaysia, Indonesia, and the Philippines
- Also native to southern China (Hainan Island) and Bangladesh (Sundarbans region)
Introduced populations:
- Mauritius, Hong Kong, New Guinea, and various Pacific islands, due to human translocation.
Preferred habitat:
- Coastal forests, mangroves, riverbanks, agricultural areas, and even urban environments.
- One of the few primates comfortable near human settlements.

Habitat & Ecology

Highly adaptable to a variety of ecosystems:
- Mangroves and tidal zones: Excellent swimmers, known to dive for crabs and mollusks.
- Tropical rainforests and dry forests: Feed in trees and on the ground.
- Urban areas: Common in temples, parks, and cities across Southeast Asia.
Often found near water, where it forages and cools off during the heat of the day.

Diet

Omnivorous and opportunistic:
- Fruits and seeds: Primary food source.
- Leaves, flowers, and roots: Supplementary vegetation.
- Animal matter: Insects, frogs, small crustaceans (especially crabs), and bird eggs.
Feeding behavior:
- Frequently forages in groups.
- Skilled at opening shells and washing food in water.
- In urban settings, known to steal food and scavenge human waste.

Behavior & Social Structure

Diurnal: Active during daylight hours, resting in trees at night.
Social organization:
- Lives in large multi-male, multi-female groups of 10–80 individuals.
- Female-dominated hierarchies; females remain in natal groups, while males disperse.
Communication:
- Wide range of vocalizations, facial expressions, and gestures.
- Grooming plays a key role in social bonding.
Intelligence:
- Demonstrates tool use, such as using stones to crack nuts or shells.
- Observed washing food or dipping it in water before eating.

Reproduction

Breeding: Non-seasonal in equatorial regions; seasonal in temperate zones.
Gestation: About 162–193 days (~6 months).
Litter size: Usually one infant per birth.
Infant care:
- Newborns cling to the mother’s belly.
- Weaning occurs at around 10–12 months.
- Juveniles remain close to the mother’s social group for protection.
Sexual maturity:
- Females: ~3–4 years
- Males: ~5–6 years

Predators

Natural predators include large birds of prey, pythons, crocodiles, and leopards.
In human-dominated areas, dogs and humans pose major threats.

Conservation Status

IUCN Red List: 🟢 Least Concern (LC)
Population trend: Stable in many regions but declining locally due to:
- Habitat destruction
- Hunting and capture for the pet trade and biomedical research
- Conflict with humans in urban and agricultural zones
Protected areas: Occur in many national parks across Southeast Asia.

Cultural and Scientific Importance

Sacred in Hindu and Buddhist cultures (e.g., “temple monkeys” in Thailand and Bali).
Widely used as a biomedical model species, known as the “cynomolgus monkey.”
Central to studies on social behavior, cognition, and zoonotic diseases (e.g., herpes B virus).

Interesting Facts

Named “crab-eating macaque” because coastal populations are often seen catching and eating crabs and shellfish.
Excellent swimmers and divers — can swim over 500 meters between mangrove islets.
Populations exhibit cultural behaviors, with local groups developing distinct feeding habits or grooming rituals.
One of the most successful primates in adapting to human presence.