GRAY SLENDER LORIS
Geographic Distribution and Habitat
The gray slender loris (Loris lydekkerianus) is a small primate found in the forests of southern India and Sri Lanka.
Gray slender lorises are prosimians—which means they are part of the oldest and most primitive group of primates—that are categorized into four subspecies: The Malabar slender loris (Loris lydekkerianus malabaricus), Mysore slender loris (Loris lydekkerianus lydekkerianus), Northern Ceylonese slender loris (Loris lydekkerianus nordicus), and highland slender loris (Loris lydekkerianus grandis).
In India, you’ll find the Malabar gray slender loris and the Mysore gray slender loris; the northern gray slender loris and the highland slender loris are endemic to Sri Lanka.
The gray slender lorises in India live in the southern areas of the Eastern and Western Ghats mountains. Their habitats are in tropical dry forests in high-altitude areas and flatter subtropical environments near plantations.
In northern and central Sri Lanka, the lorises live in dry-zone forest areas. These regions have evergreen trees, making them a bit different from the tropical lowland forests in India. Distribution rates for gray slender lorises in Sri Lanka are lower than the other subspecies.
Size, Weight, and Lifespan
Lorises are known to be small, and the gray slender loris is the smallest loris.
Weighing in at an average of 9 ounces (255 g), they measure only 8.5 inches (21.5 cm) long from head to bottom and their small limbs average 1.6–2.2 inches (4.9–5.4 cm) in length. The gray slender loris doesn’t have a tail, which may also make them appear smaller.
In the wild, gray slender lorises have an average lifespan of 12 to 15 years. In captivity, they can live up to 20 years.
The gray slender loris is lean, lanky, and not always gray. Each subspecies varies in color, and their coats are intended to help them blend into the canopy. The Indian subspecies have thick grayish-brown fur on their backs, and cream-colored fur on their underside and around their face. The Sri Lankan subspecies also have cream-colored undersides, but their main coat is a dark reddish color. All subspecies have dark brown fur around their large, forward-facing amber-brown colored eyes.
Gray slender lorises have round heads, large ears, a pointed snout, and long limbs that are equal in length. Their teeth are small and comb-like with large incisors in their lower jaw. Like humans, their thumbs are separated from the rest of their fingers so they can maintain a strong grip on the branches as they travel and hunt.
Unlike other prosimians, such as tarsiers and lemurs, all gray slender loris subspecies lack a tail, which means they are unable to acrobatically jump or leap.
The gray slender loris is an insectivore and their diet consists mostly of ants and termites. When they are feeling opportunistic, they also like to eat beetles, spiders, mollusks, and other small vertebrates.
As nocturnal hunters and foragers, slender lorises use their large, forward-facing eyes to visually detect their prey. They also have a highly advanced sense of smell that comes in handy when hunting in the dark. When eating, they sometimes use their strong grip to hang by their feet on branches while their hands hold their food.
Behavior and Lifestyle
Gray slender lorises are nocturnal tree-dwelling primates. They use all for limbs to travel along the branches in the dry forests, and their slender bodies help them climb and twist their way through the canopy.
The gray slender loris is the only species of loris that has been observed moving quickly from branch to branch. It is believed that this behavior is rare, and primarily reserved for when they feel threatened.
Compared to other solitary lorises, gray slender lorises have a more active social life. They often hunt alone, but will sometimes go out in pairs. Socialization only occurs between adult males and females, and among adults and younger lorises. Interactions between adults of the same gender are rare, likely due to their competitive instincts.
Slender lorises are sometimes referred to as “bananas on stilts.”
The gray slender loris can’t jump or leap because of their short limbs and lack of a tail.
The socially active gray slender loris is nocturnal, which means they sleep during the day and are awake at night. There are up to 7 individuals in a group: the offspring, at least one female, and at least two males.
To start their day, gray slender lorises wake up around dusk and groom each other. Then they spend their active time hunting and foraging, traveling, being social, and resting. Adult females and males forage both alone and in pairs. Female slender lorises also spend part of their time caring for their newborns, who are totally dependent on their mothers until they are 10 weeks old.
As dawn approaches, gray slender lorises sleep with their group in the same spots—usually in hollowed-out trees, crevices, or branches. Their sleeping spots are typically in the center of the main female’s territory. Individuals sleep close together and will sometimes tangle their legs together, forming a “sleeping ball.”
Gray slender lorises communicate using vocalizations and scent marking.
They make loud calls during mating season, when looking after their young, and to warn their group of predators. When foraging at night, mothers park their young among foliage and branch camouflage. Mothers might return to check in on their young, but this is not a common practice. Thirty minutes before dawn and as sleepiness kicks in, infants start to make “zic” sounds to remind their mothers of their location.
If predators are near and they feel threatened, gray slender lorises will freeze in place until the threat passes. If that doesn’t work, they growl and release a pungent odor from scent glands under their arms.
Slender lorises are very vocal when competition is around. Males competing for the same female will aggressively growl, whistle, and chitter. Females use similar vocalizations to tell males they are not interested.
Males are also intolerant of other males in or near their territory and will use urine scent-marking to claim their space. Scent marking is also used to communicate an individual’s reproductive status.
The gray slender loris’s reproductive strategy is polygynandry, which means both males and females have more than one mate.
Mating season occurs twice a year—from April to June and from October to December. Females are pregnant for an average of 5.5 months and then deliver a single offspring at a time. Twins are not uncommon and are reported to account for 22% of pregnancies. The inter-birth integral (the time in between pregnancies) averages 9 months.
Gray slender lorises are born pink, hairless, and helpless. For the first 10 weeks of life, newborns are fully dependent on their mothers. When females are foraging at night, they “park” their infants and return to them around dawn. Many times, males visit the infants while they are parked and they will groom and play with them.
Young slender lorises reach independence at 5 months and are sexually mature once they are between 10 to 18 months, but males are typically slower to mature than females. In captivity, females have shown strong maternal instincts by caring for other females’ infants.
Gray slender lorises impact their local ecosystem both as predators and prey. As insectivores, they contribute to population control for creatures like ants and termites. Lorises are also seen as prey for larger predators in their habitat, including snakes, hawk-eagles, orangutans, cats, and sun bears.
The International Union for Conservation of Nature lists gray slender lorises as Near Threatened (IUCN, 2020), appearing on the IUCN Red List of Threatened Species.
The gray slender loris is presumed to have a large, widely distributed population in India and a high tolerance for different types of habitats.
They were once considered Least Concern, but their overall population is now decreasing due to threats from deforestation and hunting throughout their home ranges—especially in Sri Lanka where their population is not widely distributed. Between 2002 and 2019, India lost 19% of tree cover and Sri Lanka lost 5.7%, which has led to habitat degradation and loss. It’s assumed that gray slender loris populations have declined by 20 to 25% during the last few generations.
In India, there are deep-rooted superstitious beliefs that lorises have medicinal and magical powers. Unfortunately, this means that loris species are often hunted for the pet trade and cultural practices. They are used in sacrificial rituals and black magic, and some are poached and killed due to the belief that they can improve eyesight in humans. Astrologers also use live lorises in fortune-telling practices and to ward off evil.
Gray slender lorises are one of the least studied primates in India, and there are no confirmed total population numbers. More research is needed to better understand the practices lorises are used for and to assess the overall sustainability of loris populations.
The gray slender loris is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival. Gray slender lorises are also classified under Schedule I of the Indian Wildlife Act (1972).
In Sri Lanka, gray slender lorises are listed under the Flora and Fauna Protection Ordinance Act No. 2 of 1937, amended in 2009. In India, the majority of the gray slender loris populations live near private land and commercial plantations. Only a small population is found in protected areas. WWF India is working to protect loris habitats with their wider conservation work in the Western Ghats mountains.
In 2010, a hotel in the heart of Sri Lanka set an example for how local commercial properties can benefit from conservation efforts. A new development project for the Hotel Jetwing Vil Uyana was halted when management realized the close proximity of gray slender loris populations. Rather than continuing with the development plan and contributing to further habitat loss, management declared a portion of the resort as a loris conservation site, becoming the first in Sri Lanka dedicated to protecting the species. The hotel now uses tourism for good by offering guided tours of loris habitats, and they have also established a Loris Conservation Fund.
Written by Maria DiCesare, March 2023