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Thai Primates

Long-tailed Macaque/Crab-eating Macaque

Science Name : Macaca fascicularis

General Characteristics : The body fur of long-tailed macaques tends to be grey-brown to reddish brown. These colors are always paler ventrally. The face is brownish-grey with cheek whiskers. The eyes are directed forward for binocular vision. The nose is flat and the nostrils are narrow and close together. The body length, not including the tail, is 40 to 47 cm. The greyish- brown or reddish colored tail is 50 to 60 cm.
The average weight for males is 4.8 to 7 kg and 3 to 4 kg for females, approximately 69% of average male weight.

Habitat / Food : Found throughout Thailand. Long-tailed macaques are "ecologically diverse." Some of the habitats in which they have been found are primary forests, disturbed and secondary forests, and riverine and coastal forests. Long-tailed macaques live successfully in urban areas of Thailand.
Long-tailed macaques are omnivores, and exploit many different food types, reflecting the diversity of habitats they can utilize. The average length of feeding bouts is 18.3 minutes. There may be on average of twenty bouts per day. They eat a wide variety of foods such as fruits, crabs, flowers, insects, leaves, fungi, grasses, and clay. Clay may be eaten for the potassium found in it, although the potassium levels in the clay are low. However, 96% of the feeding time per day is spent eating fruit. Some limited observations suggest that long-tailed macaques select fruit based on ripeness, which is based on color.

Behavior / Mating : Long-tailed macaques live in multi-male groups consisting of about thirty members. At sexual maturity, males leave their natal group, and join either bachelor groups or new social groups. Since males leave the natal group, they are subject to more predation, disease, and injury than are females. Once a male finds another group in which to reside, he may replace some of the existing high-ranking males. Male replacement itself is a process in which a foreign male adult successfully takes over a resident male's harem position. These events are highly aggressive activites, and the participating adults are usually injured. Despite aggression between males, this species is characterized by a genral lack of aggression between groups. Intergroup interactions are avoided/ When these groups meet, there tend to be high levels of aggression, involving chasing the non-resident group out of the area. Loud vocalizations and branch-bouncing are characteristic parts of these interactions. Males and females may use open mouth threats. This involves showing the enemy the incisors and canines, and pulling the ears and nose back. The alpha male is usually the one who leads the aggression by doing 90% of the branch-bouncing. Female long-tailed macaques show a conspicuous cyclicity of sexual behavior during their menstrual cycle. As they approach ovulation, females experience a swelling of the skin in the perineal region. However, there has been no direct correlation between the frequency of copulation and the degree of swelling of genital tissues. This concealment of ovulation could exist in order to persuade consorting males to stay with females longer. Gestation averages approximately 162 days. Females can produce young each year if high ranking, and every other year otherwise. Young are nursed until they are approximately 420 days of age.

Current Status : Classified as non-endangered.

Lar Gibbon/White-handed Gibbon

Science Name : Hylobates lar

General Characteristics : The fur coloring of the Lar Gibbon varies from black and dark-brown to light brown sandy colors. The hands and feet are white colored, likewise a ring of white hair surrounds the black face.
Both males and females can be all color variants, and the sexes also hardly differ in size.
Gibbons propelling themselves through the forest by swinging under the branches by their arms. Reflecting this mode of locomotion, the white-handed gibbon has curved fingers, elongated hands, extremely long arms and relatively short legs.

Habitat / Food : Found in heavily wooded areas from Southern to Northern Thailand but not on the northeast.
Lar Gibbons are threatened in various ways: they are sometimes hunted for their meat, sometimes a parent is killed in order to capture young animals for pets and the largest danger is the loss of habitat. The Lar Gibbon diet is primarily fruit constituting 50% of its diet, but leaves (29%) are a substantial part, with insects (13%) and flowers (9%) forming the remainder.

Behavior / Mating : Lar Gibbons are diurnal and arboreal, inhabiting rain forests. They rarely come to the ground, instead using their long arms to swing through the trees. With their hooked hands they can move swiftly with great momentum, swinging from the branches.
Its social organization is dominated by monogamous family pairs, with one breeding male and one female along with their offspring.
When a juvenile reaches sexual maturity, it is expelled from the family unit. However, this traditional conception has come under scrutiny. Long-term studies conducted in Khao Yai National Park in Thailand suggest that their mating system is somewhat flexible, incorporating extra-pair copulations, partner changes and polyandrous groupings. Family groups inhabit a firm territory, which they protect by warding off other gibbons with their calls. Each morning the family gathers on the edge of its territory and begins a "great call," a duet between the breeding pair. Each species has a typified call and each breeding pair has unique variations on that theme.
The great call of Hylobates lar is characterized by its frequent use of short hoots with more complex hoots, along with a "quavering" opening and closing. Gestation is seven months long and pregnancies are usually of a single young. Young are nursed for approximately two years, and full maturity comes at about 8 years. The life expectancy of the Lar Gibbons in the wild is about 25 years.

Current Status : Classified as Endangered

Dusky Leaf Monkey

Science Name : Trachypithecus obscurus

General Characteristics : Dusky leaf monkeys are widely variable in color. Their upper parts may be any shade of brown, grey, or black, whereas the under parts, hind legs, and tail are paler. The face is grey and is often marked with a patch of white fur located around the eyes and mouth. The hands and feet are capable of grasping and closely resemble those of humans. The palms and soles are hairless and usually black. The fingers of dusky leaf monkeys are well developed, but are distinct because of their opposable thumb. The nonprehensile tail varies in length and fur coverage from short and hairless, to long and hairy. Head and body length ranges from 42 to 61 cm, and tail length from 50 to 85 cm. There are no significant morphological differences between males and females except that males tend to be slightly larger and heavier than females. On average, a healthy adult male weighs 7.4 kg, whereas a healthy adult female weighs approximately 6.5 kg. Newly born dusky leaf monkeys are bright yellow or orange in color, and have a pink face; the fur changes to a greyish color within six months.

Habitat / Food : Found throughout Thailand in the middle and upper canopies of the forest. When feeding, dusky leaf monkeys pluck leaves and shoots off by hand. The diet of these monkeys consists of young leaves, shoots, and seedlings. They feed from 87 different species of trees, ingesting both leaves and fruit. In general, a dusky leaf monkey eats up to 2 kg of food per day.

Behavior / Mating : Dusky leaf monkeys are diurnal. They are very active during the day, but return to their roosts in the trees by night. These monkeys are active in the tree canopy, and prefer to stay at heights of 35 meters or higher in trees. They move from tree to tree by climbing, leaping, and running quadripedally along branches. They also pull down leafy branches and browse on them directly. These monkeys travel in groups that consist of 5 to 20 individuals. Social groups usually have one or more adult males, and two or more adult females. The adult male has three main responsibilities, which include detecting predators, holding the group together, and patrolling the boundaries of the territories. The young monkeys play in groups near the vicinity of an adult female. Overall, dusky leaf monkeys are quite social animals. Dusky leaf monkeys have a wide range of calls that are considered to be quite complex. A variety of snorts, hoots, murmurs, and squeaks are used to communicate with other members of their social group. The motion of the tail plays a significant role in maintaining balance.

Breeding in dusky leaf monkeys is intermittent and not always seasonal. Births usually take place during the months of January, February, and March, but have been documented to occur during the summer months as well. Typically one young is born. The gestation period is, on average, 145 days. Females have a menstual cycle lasting approximately three weeks. Oestrus is often accompanied by a swelling of the genitalia. The normal interbirth interval is about 2 years. Sexual maturity is reached between 3 and 4 years of age.
Current Status : Classified as Near Threatened.

Stump-tailed macaque

Science Name : Macaca arctoides

General Characteristics : Stump-tailed macaques, also known as bear macaques, have shaggy, dark brown hair covering them. They have hairless faces with red skin which darkens with sun exposure. Infants are born with white hair that darkens as they age. As they age, adult males and females show balding on the tops of their heads, much like human males, receding from the forehead towards the back of the skull. As in all other cercopithecines, they have cheek pouches that they use to store food when foraging. Stump-tailed macaques have hairless tails that are shorter than other Macaca species. Tail length ranges from 3.2 to 69 mm. This species is sexually dimorphic in many aspects of their physiology. Males are larger, ranging from 9.9 to 10.2 kg and 517 to 650 mm in height whereas females are 7.5 to 9.1 kg and 485 to 585 mm in height. Males also have much larger canines, which they use for asserting dominance within their group.

Habitat / Food : Stump-tailed macaques are found in subtropical evergreen forests below 1500 m and tropical evergreen rainforests between 1800 and 2500 m. They live in wet environments and are not found in dry forests. Stump-tailed macaques have cheek pouches that, when filled, can hold a volume equal to that of their stomach.
They forage starting in the morning through midday. They are omnivorous, but they eat mostly fruit. They also eat seeds, flowers, roots, leaves, and animals such as frogs, freshwater crabs, birds, and bird eggs. They have also been known to raid corn crops and cultivated fruits.

Behavior / Mating : Stump-tailed macaques live in groups of up to 60 individuals consisting of adult males, females, and young. Males leave after sexual maturity. They are hierarchical, with rank being reinforced through physical contact such as biting and slapping. However, compared to other macaque species, they are more peaceful and egalitarian in their social structure.
When young males move into a new group they fight to establish rank in the hierarchy.
After a disagreement or fight they have a specific ritual of reconciliation. The subordinate will present his rump to the dominant male, who will kiss or embrace the subordinate.
The subordinate will respond by "lip smacking" or "teeth chattering". Stump-tailed macaques are promiscuous in their mating behavior.
Dominance plays a big role in who gets to mate. High ranking males monopolize females in the group. However, lower ranking males have other strategies of obtaining mating opportunities.
They hang back and mate with females when the dominant male is not watching. Often referred to as the "sneaker" male strategy.
Both males and females initiate mating, though males tend to be more active when it comes to sexual behavior. Females make eye contact and present their perineal region (rump). Males approach females and sit next to them. Males chatter their teeth and grimace. When copulation is occurring, other group members often harass the pair.
Current Status : Classified as Vulnerable..

Silvered Leaf Monkey

Science Name : Trachypithecus cristatus

General Characteristics : Trachypithecus cristatus is similar in appearance to other colobines in that it is small in size, has a long tail, and dense fur. Also common to colobines is an under-bite in which the lower jaw projects out further than the upper jaw. The genus Trachypithecus is distinguished from other colobines by its prominent nasal bones, a well-developed coronal crest, and poorly developed brow ridges. There is also a reduction in the size of the first digit (thumb) facilitating the brachiating movements they utilize. The fore and hind limbs are more equal in length than most other cercopithecids. Silvered leaf monkeys get their name from the coloring of their pelage. There is some variation in the color of their fur, including brown, gray, brownish-gray, or black. No matter what the color, some hairs are gray-white and give a silver appearance. Polymorphisms are very rare; the best known is a red morph that exists in Borneo. The hands and feet are prehensile, hairless, and usually black in color. Males and females are difficult to distinguish from one another. The only visible difference is irregular white patching on the inside of the flanks of females. Males are also slightly larger than females: females are 89% of the body weight of the males. Newborns have orange fur and white colored hands, feet, and face. The skin changes color within days of birth to black, as in the adults of this species. The orange fur changes to the adult color within three to five months.

Habitat / Food : Silvered leaf monkeys primarily inhabit dense forests, but their habitat can vary somewhat depending on the region.
They have also been found in bamboo forests, on plantations, and in swamp forests. Because the monkeys are largely arboreal, they rarely leave the trees.
Occasionally, they come down to the ground, but retreat quickly if there is a threat of danger. Silvered leaf monkeys, as their name suggests, feed primarily on leaves, with a preference for young leaves.
As herbivores, they also eat some other vegetation including fruit, seeds, shoots, flowers, and buds. Some adaptations have been made to increase efficiency of digesting and processing plant materials.
The teeth have pointed cusps on their two transverse ridges.
The stomach contains bacteria for fermentation of the plants.
The stomach is also enlarged to hold a large amount of food, given that the food they eat is nutritionally poor.
They also contain large salivary glands that act to neutralize stomach acid that may cause damage if seepage from the stomach occurs.
Behavior / Mating : Individuals form groups consisting of one male and 9 to 48 females, depending on the location. Juveniles usually disperse from their natal group at maturity.
Activity for this species is from sunrise to sunset. Trachypithecus cristatus is a very shy species. Individuals are occasionally seen in the vicinity of human settlements, but retreat quickly if they feel threatened. Trachypithecus cristatus travels primarily via trees, although individuals may walk on the ground when traveling with the group.
They show a low level of aggression within the social group. Sociosexual, gestural, and vocal interactions are the common features of the social relationships of these monkeys.
This may be due to the abundance of food in their habitat and their feeding behavior of facing toward the tree while eating. These both decrease the frequency of interaction with other members of the group, resulting in less need for tight group cooperation. Groups of T. cristatus are generally one-male groups in which one male defends and mates with multiple females.
All-male groups as well as single males are also found. Occasionally, a male from an all-male unit or an individual male will challenge the male of a male/female group.
If the challenger presides over the defending male, infanticide usually occurs. Females commonly care for young of other mothers in the group, and often even allow other young to nurse.
There is no limited season for copulation, although there is a birth peak from December to May when there is an abundance of food. The gestation period is 6 to 7 months, and the estrous cycle is 24 days. Females usually give birth to no more than one infant per year. Twins have occurred, but are very rare. Females reach sexual maturity at 4 years of age, whereas males mature between 4 and 5 years of age.
Mothers nurse their young for months after birth. Females, as well as males, teach their young, play with them, and protect them from danger.
However, typically infants approach males to be carried and to play.
Young are well developed when born. Their eyes are open and their forearms are strong, allowing them to cling to the mother.
Current Status : Classified as Threatened .