The Red slender loris has a curious appearance, being a small primate with very big red eyes, rounded ears, and arms and legs which are long and slim. Its large eyes that face forward, giving it excellent night vision as well as superb depth perception. It uses its hands and feet skillfully and they are well adapted to climbing amongst the trees of its habitat. They have an opposable big toe on each foot, producing a pincer-like grip.
The Red slender loris is endemic to the south-western part of Sri Lanka. It inhabits the tropical rainforests, lowland rainforests and inter-monsoon forests of the south western wet-zone on the island.
Red slender lorises are nocturnal and arboreal. When not feeding, they are quite sociable, forming small groups where the members groom each other, sleep and play in the same area. They may sleep in tangled branches, tree hollows, or just on a branch, tightly curled. Females are higher than males in the social hierarchy. They forage alone and become active at night, and during the daylight hours they rest or sleep. These animals communicate by means of urine scent marks, to claim territory or advertise their reproductive status. If threatened, they usually remain motionless until danger has passed. Failing this, they will stare at the attacker while growling and emitting an unpleasant smell from the scent glands beneath their arms.
Little is known about the mating of Red slender lorises living in the wild. However it is suggested that their mating system is polygynandrous (promiscuous), when both males and females have multiple mates. Breeding takes place usually two times a year from May to December. The gestation period is 166 to 175 days, and birthing is once or twice each year, with usually one offspring being produced, occasionally two. Females may reenter estrus while nursing a previous litter. Infants are altricial, and cling to their mothers continuously during their first four weeks. Then they are placed in a sheltered place during their mother’s active nighttime periods. Weaning occurs at about 185 days, when the juveniles are adult size. They reach sexual maturity around 10 to 18 months (males being slower) and may first reproduce soon after.
Though protected by law within a theoretically protected habitat, these animals are regularly hunted for “medicinal” use of their body parts, a major threat that many animals in Asia share. They are also killed by cars when crossing roads and electrocuted on power lines when attempting to climb along a “vine”. Huge habitat loss as a result of illegal logging, and the development of cinnamon, palm oil, rubber and tea plantations, is likely sealing off any chance of recovery while humans are active in the area.
According to the IUCN Red List, the total Red slender loris population size is fewer than 2,500 mature individuals. There are two subspecies of red slender loris: the western red slender loris is estimated to number approximately 1,500 individuals; the Montane slender loris is estimated to number around 80 individuals. Overall, currently Red slender lorises are classified as Endangered (EN) and their numbers today are decreasing.
As insectivores, Red slender lorises may have an impact on the insect community but it's not confirmed.