North Sumatran Leaf Monkey

• Common Names: North Sumatran leaf monkey, Thomas’s langur
• Taxonomy Classification Year: 1892
• Monkey Size: 92 to 147 cm (36.22 to 57.87 in)
• Skin Color(s): Black, Gray and White
• Habitat: Forest, rainforest
• Diet: Omnivorous
• Native Countries: Indonesia

The North Sumatran leaf monkey^[1] (Presbytis thomasi), also called Thomas’s langur, is a primate species in the Cercopithecidae family.

• This Old-World monkey is native to North Sumatra, Indonesia. Its natural habitat is tropical or subtropical dry forests.
• North Sumatran leaf monkey has a very distinctive appearance. Because of their unique facial coloration, it’s easy to distinguish North Sumatran leaf monkeys from other primates.
• The white fur on the underside and arms (in contrast to the black fur surrounding the rest of the body) continues to the neck.
• Two more white stripes, beginning at the crown, run down the sides, meet at eye level in a V-shape, and run around it.
• A silvery-purple undercoat forms rings around the orange-brown eyes. In the dark shade, you can see their pink skin. The same pink skin covers the snout.

The north Sumatran leaf monkey feeds on these plant matters namely^[¶]:

• Bishopwood (Bischofia javanica)
• Cowa Fruit (Garcinia cowa).
• Weeping Fig (Ficus benjamina).
• Argus Pheasant Tree (Dracontomelon dao).
• Council Tree (Ficus altissima).
• Clustertree (Ficus racemosa)
• Pulasan (Nephelium lappaceum)
• Fig (Ficus)
• Javanese Treebine (Cissus nodosa).
• Ilang-Ilang (Cananga odorata)
• Brown-Woolly Fig (Ficus drupacea).
• Myrobalan (Terminalia bellirica)
• Oriental Trema (Trema orientalis).
• Jacareuba (Calophyllum brasiliense)

• The North Sumatran leaf monkeys spend most of the day in groups resting, moving, or feeding.
• In males and females, a dominance hierarchy may depend on an individual’s age or ability to defend themselves against other group members.
• Although this leaf monkey is known to have a calmer demeanor in responses and gestures towards its conspecifics than other primates, competition within groups has been observed.
• Many factors influence a woman’s decision to leave her group and join another. These include food competition, risk of predation, and avoidance of inbreeding.
• Vocal communication is more intense and common at dawn. It is used in various situations, such as attacking, relocation, establishing sleeping positions, and defending mates and territories.