Gray slender loris (Loris lydekkerianus)

Also known as: grey slender loris
Synonyms: Loris tardigradus grandis
KingdomAnimalia
PhylumChordata
ClassMammalia
OrderPrimates
FamilyLorisidae
GenusLoris (1)
SizeBody length: 26 cm (2)
Weight265 g (2)

The gray slender loris is classified as Least Concern (LC) on the IUCN Red List (1), and is listed on Appendix II of CITES (cites). Four subspecies are currently recognised: Loris lydekkerianus grandis (highland slender loris) and Loris lydekkerianus nordicus (dry zone slender loris) are both classified as Endangered (EN), and Loris lydekkerianus lydekkerianus (Mysore slender loris) and Loris lydekkerianus malabaricus (Malabar slender loris) are classified as Near Threatened (NT) (1).

The gray slender loris is a curious looking primate, with its large, round eyes and thin, elongated limbs (3). Despite its name, this loris is not always grey and some individuals can appear quite reddish; each of the four subspecies varies in coat colour (2) (4). The eyes are surrounded by a black ring, and a white line that extends down onto the nose separates the eyes (3). The gray slender loris is a tree-dwelling species that moves along branches on all fours, and stretches between thin end branches in order to reach a neighbouring tree (3). Its tiny hands enable this loris to grip the smallest of branches (5), and a special network of blood vessels in the wrists and ankles allow it to grip tightly for a few days without suffering any muscle cramp (3). Like all lorises, the gray slender loris has a nail on each of its digits except for the second digit of each foot, which instead possesses a relatively long claw; called the ‘toilet’ claw, the loris uses this when grooming (3). The lower incisors and canines of the loris are also used in grooming. These teeth, which form a comb-like arrangement, are also specially suited to feeding on insects or tree gum. A cartilaginous brush on the underside of the tongue enables the loris to clean out particles from between its lower teeth (3).

The gray slender loris occurs in southern and eastern India and Sri Lanka (1). Within this large range, each subspecies occupies a different area. The Mysore slender loris (L. l. lydekkerianus) inhabits the Eastern Ghats, in southern and eastern India, and the Malabar slender loris (L. l. malabaricus) occurs along the west coast of India and in the Western Ghats (1). The other two subspecies, the highland slender loris (L. l. grandis) and the dry zone slender loris (L. l. nordicus), both occur in Sri Lanka, in the central province and north central dry areas respectively (1).

The gray slender loris has been recorded in a range of habitats including forest, plantations, and dry shrub jungles. It appears to prefer degraded forests, rather than primary forest, and is often associated with areas near human habitations (1).

The gray slender loris is a nocturnal primate that hunts primarily using vision (2) (6), and therefore has remarkable eyes that are adapted to this life. A special layer at the back of the eye reflects light back through the retina, resulting in increased stimulation of the photoreceptors, and allowing vision in very low levels of light (3). The gray slender loris feeds primarily on insects (1), particularly ants, although the gum from trees is also eaten (6). This arboreal species remains in the trees to hunt insects, and adopts acrobatic positions in order to capture its prey (6). With its feet clinging to a branch in a vice-like grip, the gray slender loris can reach up with both arms to snatch an insect from the air, or hang down from the branch to pluck insects from the undergrowth (6). Often, the gray slender loris will silently stalk its prey, before reaching out to grab it, in a hunting manner that has been compared to a cat (6).

Although this species often forages alone (5), it is actually a social primate that sleeps during the day in groups of up to seven individuals (1), and interacts within the group throughout the night; physical contact and grooming are reported to be essential components of slender loris behaviour (5). Each group typically comprises one female, her dependent offspring and one or more males (5). The males, which have home ranges almost twice the size of those of females, act aggressively toward any male from outside their own sleeping group, while adult females rarely interact with each other (5). Females may give birth to twins, twice each year (5); one study revealed that these two births take place during April / May, and October to December after a gestation period of 5.5 months (7).

Numerous human activities threaten the gray slender loris throughout its range. Habitat loss has impacted this species in both Sri Lanka and India (1), and the plantations that the loris can be found in are an unstable habitat, as they can be harvested at any time (4). This nocturnal primate is also killed by road traffic, electrocuted on un-insulated power lines, captured for the pet trade (1), and hunted for use in traditional medicines (1) (2). In certain areas, such as the Indian state of Tamil Nadu, people believe that oil taken from the flesh of the slender loris can treat tuberculosis and an extract of the loris' eye can help cure eye diseases (2); these 'medicines' have no scientific foundation and are contributing to the gray slender loris being reduced to small pockets of existence (2).

Although the gray slender loris does receive protection under the Indian Wildlife Act of 1972 (1), and a few populations are found in protected areas (1), further conservation actions are urgently needed to ensure the survival of each of the subspecies (2). One of the main factors that hinder conservation of this species is the lack of information concerning this loris' behaviour in its natural habitat (2), and thus further studies and surveys on the gray slender loris are required (1).

Also recommended is the implementation of speed breakers on roads that run through critical loris habitat, in order to reduce the number of road deaths, plus the planting of trees to link forest patches, which will reduce the chance of a loris either travelling across a road, or using a powerline which risks electrocution (7). An educaion programme has been launched in Sri Lanka which aims to increase the public's awareness of the slender loris (1), but further public awareness campaigns are needed in other parts of this species' range. This, combined with strong measures against offenders, will hopefully lessen the numbers of lorises that are killed through needless hunting (7).

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  1. IUCN Red List (January, 2010)
    http://www.iucnredlist.org
  2. Huxley, V.A.J. (2009) Endangered slender loris needs conservation. Current Science, 96(12): 1563.
  3. CITES (January, 2010)
    http://www.cites.org
  4. Macdonald, D.W. (2006) The Encyclopedia of Mammals. Oxford University Press, Oxford.
  5. Kumara, H.N., Singh, M. and Kumar, S. (2006) Distribution, habitat correlates, and conservation of Loris lydekkerianus in Karnataka, India. International Journal of Primatology, 27(4): 941-969.
  6. Nekaris, K.A.I. (2006) Social lives of adult Mysore slender lorises. American Journal of Primatology, 68: 1171-1182.
  7. Nekaris, K.A.I. (2005) Foraging behaviour of the slender loris (Loris lydekkerianus lydekkerianus): implications for theories of primate origins. Journal of Human Evolution, 49: 289-300.
  8. Radhakrishna, S. and Singh, M. (2002) Conserving the slender loris (Loris lydekkerianus lydekkerianus). National Seminar on Conservation of Eastern Ghats, Tirupati, Andhra Pradesh.