Pygmy Slow Loris

The pygmy slow loris is a small, nocturnal primate found east of the Mekong River in Vietnam, Laos, eastern Cambodia and China. It lives in tropical dry, semi-evergreen and evergreen forests, moving along branches with slow, deliberate movements in search of prey and never leaping. Adults measure around 19 to 23 cm, with a very short tail, and weigh about 450 g. Its diet includes fruits, insects, small animals, tree sap and floral nectar. It lives in small groups, usually with one or two offspring. The lower teeth form a comb-like toothcomb used for scraping resin from tree bark.

About the pygmy slow loris

The pygmy slow loris is a small, nocturnal primate from Southeast Asia and one of the slow lorises, a group of slow-climbing strepsirrhine primates. It lives in forests east of the Mekong River in Vietnam, Laos, eastern Cambodia and southern China. It is known for its slow, deliberate movements and a toxic bite.

For most of its scientific history it was placed in the slow loris genus Nycticebus. In 2022, researchers combining body, behavior, chromosome and DNA evidence moved it into its own genus, so its current scientific name is Xanthonycticebus pygmaeus. Genetic work suggests it diverged earlier than the other slow loris species, perhaps beginning 2.7 million years ago. Two species of pygmy loris are now recognized: the northern pygmy loris (X. intermedius) of northern Vietnam, Laos and China, and the southern pygmy loris (X. pygmaeus) of southern Vietnam, Laos and Cambodia.

It is small. The head and body measure 19.5–23 cm (7.7–9.1 in), and the tail is a stub averaging just 1.8 cm (0.7 in). Weight usually falls between 360 and 580 g (13–20 oz), with males and females about the same size. Body weight swings with the seasons: animals get about 50% heavier in winter than at their summer low, mostly by eating more, and individuals up to 700 g (25 oz) have been recorded. The extra weight helps them survive winter, when food is scarce.

The fur is reddish. The face and top of the head are rufous, with dark brown rings around the eyes, a white stripe running from the nose up the forehead, and silvery grey on the sides of the head and upper lip. A rufous to brownish-black stripe often runs down the back, and the upper body may be frosted with silvery hairs; both features vary with the season. The ears are small and black, and the hands and feet are silvery white. Like other strepsirrhine primates, it has a reflective layer behind the retina, the tapetum lucidum, that boosts night vision. Its lower front teeth tilt forward to form a toothcomb, used for grooming and for scraping gum from trees.

Behavior and diet

The pygmy slow loris is nocturnal and lives in the trees. It crawls slowly along branches and, unlike other primates, does not leap. It is most active on dark nights and least active on cold, moonlit ones. In the wild it is usually seen alone or in small groups of two to four, often a parent with one or two young.

Its defense is unusual. Glands on the inside of the elbows, called brachial glands, produce a clear, oily fluid. When startled, the loris licks these glands, and the secretion mixed with saliva becomes a noxious toxin that is delivered in a bite. It also spreads the secretion onto its head. One analysis found more than 200 chemical components in the fluid, including a protein similar to an allergen in cat dander, which may explain severe allergic reactions (anaphylaxis) in susceptible people.

Scent matters in its social life. Males mark territory boundaries with scent and mark over rivals' marks to show off their competitive ability, and females prefer males whose scent they know. Calls include a short whistle, mother-infant contact calls, and whistles, chittering and growls during the breeding season.

The diet is mostly gum. One Vietnamese study found tree gum made up about 63% of the diet and animal prey about 33%. The loris gouges bark with its teeth to make trees release sap, then licks it up for anywhere from one to twenty minutes at a time, usually more than 8 m (26 ft) off the ground. Gum is less nutritious than insects or fruit, but it is available all year and lets the loris live on a low-energy budget. It also eats termites, ants and other insects, grabbed with one or both hands while standing or hanging upside-down, along with fruit, small animals and nectar. In the cold northern winter, when temperatures drop as low as 5 °C (41 °F), it saves energy by cutting back movement, sometimes to complete inactivity.

Females come into season only once a year, for four to five days between late July and early October in captivity, with births from early February to mid-March. Pregnancy lasts 184–200 days, about six months. Litters are one or two young, and twins are common. For the first days the infant clings to its mother's belly. At about a week old, mothers "park" their young on a branch while they forage, and the young start following their mothers at about two weeks. Weaning comes at around 24 weeks. Females can conceive at 16–18 months, and the species lives about 20 years.

Range and habitat

The pygmy slow loris is found only east of the Mekong River, in Vietnam, Laos, eastern Cambodia, and Yunnan province in southern China. In China it has been recorded in only four counties of Yunnan. It lives in tropical dry forest, semi-evergreen and evergreen forest, secondary forest, and broadleaf and mixed forest, and it favors closed-canopy forest. Field surveys in Laos and Vietnam found it at very low encounter rates of 0.05–0.08 lorises per kilometer walked.

Because it is nocturnal, lives high in the trees and occurs in politically unstable areas, population data are scarce. Estimates from the 1980s ranged wildly, from about 600–700 animals to roughly 72,000, which shows how hard the species is to count.

Conservation status

The pygmy slow loris is listed as Endangered on the IUCN Red List, most recently assessed in 2025, and has been on Appendix I of CITES since 2007.

Habitat loss has been severe. Defoliants such as Agent Orange used during the Vietnam War, followed by ongoing forest clearing, cut Vietnam's forest cover to 30% of its original area by 2003, and only a tenth of that remaining forest was the closed-canopy type the loris prefers. In Yunnan, nearly all primary evergreen forest has gone, and the Chinese population is estimated at fewer than 500 animals and may be locally extinct. The loris has also been wiped out in northern Vietnam, where it was seen as a crop pest.

Hunting and trade are the other major threat. The species is taken for traditional medicine, as a pet and for food. In Cambodia it has been the third most common mammal for sale in markets and the most requested animal in traditional medicine shops in Phnom Penh. Large numbers move illegally through Laos and Vietnam to China. Between 1998 and 2006, 70% of pygmy slow lorises seized by authorities died before reaching a shelter. Because the species breeds slowly, wild populations cannot keep up, and field sightings have fallen sharply.

The species is legally protected in Cambodia, China and Vietnam, where Vietnamese law has given it the highest level of wildlife protection since 1992, but enforcement is weak. It occurs in at least six national parks and twelve nature reserves. Confiscated animals in Vietnam are often taken to a rescue center for reintroduction to the wild. In North America, a Species Survival Plan was set up for the species in 1994 to maintain the genetic diversity of the captive population.