5 species of non-human primates can be seen in Sri Lanka.
Those are,
Toque macaque – Macaca sinica (in Sinhala Rilawa) has 3 subspecies,
Purple-faced, leaf langur – Semnopithecus vetulus (in Sinhala - Kalu Wandura) – 4 subspecies),
Gray langur -Semnopithecus prium (in Sinhala – Alu Wandura )
Red slender loris (Loris tardigradus 2 subspecies)
and
Gray slender Loris (Loris nycticeboidus - 2 subspecies).
The most important things to know about these non-human primates are, that these animals are unique to Sri Lanka and cannot be seen naturally in any other country in the world. So, if they become extinct, they will be eliminated from the world. The fact that about 12 subspecies of primates can be seen on this small island confirms that Sri Lanka has a high biodiversity. This helps to create biological balance on the island.
Among these 12 subspecies, the langur subspecies - Purple faced leaf langur (Semnopithecus vetulus nestor) found in the western province and the Loris species - Red slender loris, found in Hortan plateau have been included in the list of the 20 most rapidly disappearing primates in the world.
Lorises (in Sinhala “Unahapuluwa”)
Gray slender loris
2 subspecies,
Red slender loris (Loris tardigradus ) 2 subspecies. Habitat is the wet zone of Sri Lanka
and
Grey slender Loris (Loris nycticeboidus) 2 subspecies. In dry zone
Lorises are small-bodied primates that are active at night. In keeping with their nocturnal habits, they have huge eyes, and they move through the shrubs and trees in a slow deliberate manner. They live either singly or in small family groups of a female and one or two of her young. They primarily eat insects and small prey as well as fruits.
Toque macaques - Macaca sinica (in Sinhala Rilawa)
The species owes its name to a type of hat, known as "toque" that was popular in 16th century England.
Macaques can be considered the most widespread primate species in Sri Lanka. 3 Macaque subspecies are distributed in the climatic zones of the island.
That is
(1) Dry zone macaques (Macaca sinica sinica),
(2) Wet zone macaques (Macaca sinica aurifrons) and
(3) The montane macaques (Macaca sinica opisthomelas).
Although to the untrained eye, all the macaques in Sri Lanka look the same, these 3 subspecies can be distinguished based on external characteristics.
It should be kept in mind that these 3 relevant subspecies can only be seen in those respective regions. As mentioned before, if they become extinct from those respective regions, they will be eliminated from the world.
Macaques' feeding pattern is omnivorous. That is, they have the ability to enjoy any type of food. Examples include fruits, vegetables, grains, insects, and other small animals. These animals prefer to live very close to human habitation based on their wide eating pattern. It has provided them an opportunity to easily adapt to any environmental condition. They can be seen in trees as well as on the ground.
Toque macaques live in social groups, of normally about 25 members comprising one to three matrilineal families, and one or more adult males that have immigrated from other social groups. In some cases, more than a hundred members can be seen in one herd.
Langurs
Purple faced leaf langur
Two types of langurs can be identified on the island. These animals have relatively large bodies compared to macaques.
One of these species is the Purple-faced Langur - Semnopithecus vetulus (in Sinhala “Kalu Wandura“) and is divided into 4 subspecies according to the region where they are spread. These sub-species are,
Southern purple-faced leaf langur (Semnopithecus vetulus vetulus),
Western purple-faced leaf langur (Semnopithecus vetulus nestor),
Montane purple-faced leaf langur (Semnopithecus vetulus monticola).
Northern purple-faced leaf langur (Semnopithecus vetulus philbricki),
These langurs are mainly herbivores and live in relatively small groups. Since these animals are full tree dwellers, they hardly come down to the ground. Another important point is that they tend to live away from human society. However, due to the limitation of their habitat in urban areas, they live near human settlements.
The other species of monkey is the Tufted Gray langur - Semnopithecus priam
(Sinhala name “Alu Wandura”)
These monkeys are herbivores and can be seen in herds with a large number of members compared to black monkeys. They, like macaques, live near human habitations and are seen roaming on the ground as well as in trees.
Along with these black langurs, there are also a group of snow-white monkeys around the Sinharaja rainforest. They are members of the black langur subspecies (Semnopithecus vetulus), which live in the lowland wet zone. Some are completely white except for the face, while others have black spots over their white body.
In groups, white mothers have black children and black mothers have white children.
Although the skin and eyes of albino animals are pink, these langurs' eyes are not. Therefore, these white monkeys are not caused by albinism..
Torque macaque