The unique Long-tailed macaque exhibits an extremely long tail, which is longer than its height from the head to rump. This primate has a pinkish-brown face and white spaces on its eyelids, near the nose. Another conspicuous characteristic of this species is the crest on the head top, formed by the hairs on the head, sweeping back over the forehead. Male Long-tailed macaques are distinguished by mustaches as well as cheek whiskers around their faces. Females, on the other hand, have beards and cheek whiskers.
The Long-tailed macaques are found throughout south-eastern Asia. Their range extends from the southeastern tip of Bangladesh southwards to Malaysia and the Maritime Southeast Asia islands (including Sumatra, Java and Borneo), offshore islands, the Philippines as well as the Nicobar Islands in the Bay of Bengal. Ideal habitat for this species is disturbed areas and forest periphery. However, these primates occur in different habitats from primary lowland rainforests and disturbed, secondary rainforests to shrubland, riverine and coastal forests of nipa palm, mangroves and even human settlements.
These primates are diurnal and highly social creatures, forming groups of 1 or more males as well as 3 - 20 females with their young. As a general rule, the majority of mature individuals of a group are females. Males usually disperse upon reaching maturity to form new groups or join bachelor herds. Males live in a well-defined linear hierarchy system, where individuals are ranked depending on age, size, and fighting skills. Young females, on the other hand, remain with their natal group, forming the core of the group. Related females typically live in close relationships. Overall, females of this species commonly practice mutual grooming, where lower-ranking individuals groom higher-ranking ones, due to which the former avoid intimidation, get support during conflicts as well as access to limited resources of the group.
As omnivorous animals, the Long-tailed macaques consume food of both plant and animal origin. They eat fruits, crabs, flowers, leaves, fungi, grasses and clay, supplementing this diet with various insects.
Long-tailed macaques exhibit polygynous (one male mates with multiple females) and polygynandrous (promiscuous) (multiple males mate indiscriminately with multiple females) mating systems. Most births occur in May-July, during the rainy season. Gestation period lasts for 162 days, after which high ranking females usually give birth to a single infant at an interval of 390 days, while others produce offspring every 2 years. The newborn baby is nursed until 420 days old. The age of reproductive maturity is 6 years old in males and 4 years old in females.
Threats to the population of this species vary, depending on geographical location. For example, Long-tailed macaques in the Philippines are hunted for food and sport. On the other hand, those in the mainland areas (including Cambodia and Vietnam) are commonly captured by humans: while females are taken for breeding, males are used in laboratory research. In certain parts of their range, these animals are considered pests and hence persecuted. In other areas, they face loss of their natural habitat. However, these primates are highly adaptable by nature and are capable of living in a wide range of environments.
The exact number of the Long-tailed macaques' total population is currently unknown. However, as reported on the IUCN Red List, specific populations have been estimated in the following areas: eponymous sub-species on the Nicobar Islands - around 4,800 individuals; eponymous sub-species on Con Son - less than 1,000 animals; Bangladesh - under 100 individuals. Further, as reported by the Cities resource, the population in Malaysia is around 742,000 individuals, including 258,000 macaques around urban areas such as Kuala Lumpur. The population of Long-tailed macaques is presently decreasing, although the animals are listed as Least Concern (LC) on the IUCN Red List.