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Slender Loris

Loris tardigradus

p0000000472 Slender lorises are one of three species of loris maintained at the Lemur Center (the others are pygmy slow lorises and slow lorises). All three of these species are members of the family Lorisidae which includes lorises, galagos and pottos and consists of 9 genera and over 25 species found in Africa south of the Sahara, southern India, Sri Lanka, southeastern Asia and the East Indies. Lorises have a tail either very short or completely absent, and their heads and eyes are round, with small ears which are almost completely hidden by fur. The forelimbs and hindlimbs of lorises are nearly equal in length.

All lorises have extremely strong fingers and toes, and they are capable of maintaining a powerful grip with either hands or feet for astonishingly long periods of time. They are arboreal and nocturnal, sleeping by day in hollowed out trees, tree crevices or branches. Generally they sleep curled up in a ball, with their heads tucked up under their arms. When they move, they do so with slow deliberate hand-over-hand movements, moving along as easily under a branch as above. They are capable of moving quickly if alarmed, but they do not jump or leap.

In North America, there are only about 10 slender lorises remaining in captivity, and the animals are quite aged. Unfortunately, it is unlikely that a sustainable captive population can be maintained in North America. The Lemur Center only has 1 slender loris, Abu.

Feeding

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Like the other lorises, the slender loris is a solitary, nocturnal feeder. In this species, however, it appears that adult males and females sometimes forage in pairs.

Slender lorises are omnivorous, but unlike the other loris species, they depend on insects as their primary food source. They have a highly developed sense of smell, which they use to locate insect prey in the dark. In addition, they have been observed eating eggs and small vertebrates. Slender lorises also feed on plant material, including young leaves, shoots, flowers, and fruit with hard rinds.

Slender lorises can move fast if alarmed. Although they spend most of the time in the trees, they occasionally come to the ground. They catch their prey using a ‘sneak, spring, and grab’ method: They stalk along a branch, slowly approaching an insect or other food item. When they get close, they crouch and leap suddenly, grabbing the animal or insect with their nimble hands. As carnivores, slender lorises do not tend to be picky, with research showing that they consume every part of their prey, which may include feathers, bones and hard exoskeletons.

Reproduction

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The reproductive strategy of the slender loris varies slightly from that of the other loris species. While most individuals live alone, some also live in pairs. There are two distinct mating seasons in the wild, one from April to May and another from October to November. In captivity, the slender loris breeds year round. During mating season, the female is in estrus for a period of 29-40 days. During mating the female hangs from a branch by all four limbs and will completely support the male’s weight, in addition to her own.

Gestation ranges from 166-169 days. Mothers normally give birth to one infant at a time, but twins have been reported at a rate of about 22%. Newborns cling to their mothers’ fur and are born pink and almost entirely furless. The maternal instinct is apparently strong, as captive females have been observed caring for the infants of other females.

Offspring reach sexual maturity between 10 and 18 months (more slowly in males) and may give birth themselves soon after.

Social Behavior

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Slender lorises are solitary, nocturnal foragers who are active throughout the night. During the day, they sleep curled up in a ball in hollow trees or in the crook of a branch, bracing themselves by clutching nearby twigs with their spindly arms and delicate hands.

While generally solitary, slender lorises have been seen foraging with a mate. As in other loris species, males will not tolerate the presence of other males in their territory. Individuals communicate using urine scent marks, claiming territory or advertising their reproductive status to others.

If threatened, slender lorises usually freeze and remain motionless until the danger has passed. If this fails, they will stare at their attacker and growl while emitting an unpleasant odor from scent glands under their arms.

Habitat/Conservation

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The slender loris is found in India, below about 15º latitude, and on the island nation of Sri Lanka. Its range does not overlap with that of the other two loris species. Slender lorises are well-adapted to exploit a range of habitats. They are often found in low, swampy areas or humid tropical rainforests, but have also been observed in drier areas, including scrub and semi-deciduous forests. They can also adapt to greater temperature fluctuations than the other loris species, and will inhabit cool montane forests up to an elevation of about 1850 meters (6070 ft.).

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Like the other lorises, this species faces a persistent threat from deforestation. In parts of India, only patchy remnants of forest remain, and the animals that live there consist of small, isolated populations. In Sri Lanka, most of the original habitat has disappeared, and research suggests that slender lorises are not taking up residence in the pockets of undisturbed forest that remain. It is unknown what impact, if any, the 2004 tsunami had on slender loris populations in the wild.

Like all lorises, members of this species are hunted, primarily for medicinal use.

Fact Sheet

Order: Primates; Suborder: Prosimii
Superfamily : Lorisoidea; Family: Lorisidae
Genus: Loris; Species: tardigradus

Related Species :

The slow loris (Nycticebus coucang) and pygmy slow loris (Nycticebus pygmaeus) are similar in behavior to the slender loris.

Key Facts

Adult Size : 0.3 – 0.6 pounds
Natural Range : India and Sri LankaSocial life : Solitary nocturnal forager
Habitat : Tropical forest, woodland and thorny scrub jungle
Diet : Insects, young leaves, shoots, hard-rind fruits and flowers, occasional eggs and small vertebrates
Lifespan : over 15 years in captivity
Sexual maturity : 10-18 months
Mating : Every 9.5 months
Gestation : 166 – 169 days
Number of young : 1 – 2 offspring every 9 – 10 months
DLC Naming theme : Indian names (Rajiv, Kiran, Jagan, etc.)

Interesting Facts

  • Slender lorises roll up in a ball to rest.
  • Slender lorises are incapable of jumping even short distances, but they can bridge significant gaps in the trees with their long limbs.
  • Female slender lorises have two pairs of mammary glands.
  • Female slender lorises hang upside-down during mating.
  • Slender lorises are often referred to as “bananas on stilts.”
  • Slender lorises’ main form of defense is to freeze until the danger passes.

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