Nycticebus pygmaeus

Geographic Distribution and Habitat
The pygmy slow loris, also called the lesser slow loris, is a small-bodied prosimian found in Southern China, Eastern Cambodia, Laos, and east of the Mekong River in Vietnam. They inhabit rainforests and evergreen forests and are also found in secondary and degraded forests and bamboo plantations. Throughout their range they share habitat with the Bengal slow loris (Nycticebus bengalensis).

Pygmy slow loris range, IUCN 2020

Size, Weight, and Lifespan
As their name suggests, pygmy slow lorises are the smallest of the eight species of slow loris. On average, adults weigh approximately 1.1 pounds (0.49 kg), although their weight can fluctuate substantially with the seasons. Adults measure around 7.7–9.1 inches (0.2–0.23 m) in length, excluding their (very short) tail.

Although the average lifespan of wild individuals is not well known, they can live to over 20 years in captivity.

The pygmy slow loris has a reddish-brown pelage, although this can change in color with the season, possibly due to changes in their diet. They have pale faces except for reddish-brown markings around their eyes, which connect to the reddish-brown coloration on their heads.

One of their most notable features is their large, round eyes, typical of nocturnal primates who need to see well in the dark. They also have round heads and small, round ears. Their forelimbs and hind limbs are of a similar size and they have very short tails. Similar to other prosimians, they have incisors that form a tooth-comb, which is used for grooming and foraging.

Male and female pygmy slow lorises have a very similar appearance and do not seem to display any sexual dimorphism.

Photo credit: David Haring/Duke Lemur Center/Creative Commons

​Pygmy slow lorises are omnivorous, eating fruit and other plant matter, insects, and other small prey items. Gum and plant exudate are major food sources for the pygmy slow loris. They obtain this by scraping branches with their teeth to release gum and by licking plant exudate from the branches.

Behavior and Lifestyle
Pygmy slow lorises live an arboreal lifestyle and rarely descend to the ground, instead remaining in the trees. They have a very strong grip and can hang from branches by their hind limbs for long periods. They to move slowly and, although they can move quickly if startled, they do not jump or leap.

Nocturnal foragers, they can spend up to 19 hours sleeping each day and tend to sleep curled up in a ball in the hollows of trees or on branches. During winter, they can become inactive for extended periods of time, slipping into a torpor in order to save energy when food is less available.

Brachial glands on their upper arms produce a secretion that, when mixed with saliva, becomes toxic. When pygmy slow lorises are threatened, they stretch out their arms to activate the flow of the secretion and lick the brachial gland to mix their saliva with it, transferring the secretion into their mouths. Their bite becomes toxic. This makes the pygmy slow loris one of the very few species of venomous primates with a bite that can incapacitate potential predators, which might include pythons, eagles, and, of course, humans.

What Does It Mean?

A recurring period of sexual receptivity and fertility in many female mammals.

A substance, such as gum, sap, or resin, which flows from the vascular system of a plant.

The fur, hair, or wool of a mammal.

The most primitive of the primates. “Prosimian” means pre-monkey. The living (extant) prosimians are in the suborder Prosimii, which includes four families of lemurs, the bushbabies (galagos), lorises and pottos, and the tarsiers.

Olfactory communication:
Communication between individuals that uses the sense of smell. In primates, scents used in olfactory communication are usually produced from urine, feces, or secretions from skin glands.

​Sexual dimorphism:
Distinct difference in size or appearance between the sexes of an animal in addition to difference between the reproductive organs themselves.

Slash and burn agriculture:
​A method of unsustainable farming where farmers clear land by cutting and burning flora in order to create an empty field—a “swidden”—for cultivation. Such practices are detrimental to local ecosystems.

The incisors on the lower front jaw of some animals are grouped as if to form a comb. The tooth-comb is used by these animals to groom and clean their fur or hair.

A sleep-like state in which the body decreases physiological activity.

Visit the Glossary for more definitions

Daily Life and Group Dynamics 
​Pygmy slow lorises seem to lead a mostly solitary lifestyle. Males and females do not appear to accompany each other when not breeding and they do not live in groups like many other primates. However, the territory of a male may overlap with that of several females. Males rarely share a territory with one another.

Probably due to the dense forest that they inhabit (which limits visual communication), olfactory communication seems to be very important to the pygmy slow loris. Both females and males display urine marking, and males in the wild are believed to use urine to scent-mark the boundaries of their territories. They also produce scent from their brachial glands, but the role of this in communication is less understood.

Likewise, the vocalizations of the pygmy slow loris are not well documented, although some types of call have been identified including a hiss to ward off potential predators, a short whistle made by estrus females, and contact calls between mothers and infants that consist of chirps, clicks, and squeaks.

Fun Facts

The pygmy slow loris is the smallest of 8 species of slow loris.

They are one of the few primates that have a venomous bite, produced by mixing their saliva with secretions from their brachial glands. 

Using their super strong grip, they can hang from branches for hours at a time.

Critical threats include habitat loss, their use in traditional medicine, and the illegal pet trade.

Reproduction and Family
Reproduction is seasonal with estrus occurring between July and October every year when each female has a window of only 4–5 days in which to mate with a male. Since a male’s territory can contain multiple females, a male will probably mate with several different females during the mating season. Following mating, and after a gestation period of 6 months, females give birth between January and March. They can give birth to a single infant or twins, and even triplets and quadruplets have been born in captivity.

When infants are very young they cling to their mothers’ bellies. From their first week of life, infant slow pygmy lorises are left alone, “parked” on a branch while their mothers forage for food. From their second week however, they start to follow their mother as she leaves to forage. Infants become weaned at approximately 133 days. Females reach sexual maturity sometime between 9 and 16 months, whereas males do not reach sexual maturity until around 18–20 months.

Photo credit: David Haring/Duke Lemur Center/Creative Commons

Ecological Role
The impact of the pygmy slow loris upon its environment is not yet well understood. However, since they eat fruit as part of their diet, it is likely that they may play a role in seed dispersal.

Conservation Status and Threats
The pygmy slow loris is classified as Endangered by the International Union for Conservation of Nature (IUCN, 2015), appearing on the IUCN Red List of Threatened Species. The species is suspected to have undergone a decline of more than 50% over the last three generations (24 years, given a generation length of 8 years). It is suspected that the population will continue to decline by at least 50% over the next 24 years. Population reduction is due primarily to hunting for pet trade, food, and ‘medicinal’ purposes in much of its distribution range, resulting in drastic declines which are reflected in high prices in the market and reduced numbers sold. In addition, the species has been also impacted by and continues to be impacted by habitat loss from human settlements and agriculture especially cashew plantations, corn and rice paddies.

A critical threat to the survival of this species is their use in traditional medicine in Asia, where hunted lorises are available to buy at local markets. Additionally, following a series of online videos showing pygmy slow lorises being kept as pets, the number of people eager to keep them as pets has increased. Lorises kept as pets or as props for tourist photos are subjected to a great deal of suffering; their teeth are often pulled to stop their venomous bites and they are often kept in cramped, brightly lit, and unsuitable conditions. This trade often involves removing lorises from the wild, further damaging the already declining wild population.

Another severe threat to the survival of the pygmy slow loris is habitat degradation. Much of the forest cover in its native range has been removed in the past few decades. In Vietnam, only 30% of the original forest cover remains. Where forest remains, it is often highly fragmented, which hinders the movements of lorises. Slash and burn agriculture has resulted in the eradication of the pygmy slow loris from large areas.

Conservation Efforts
The NGO International Animal Rescue recently launched a campaign to educate people about the suffering caused to slow lorises by the pet trade in the hope of deterring them from participating in this trade.

However, further action is needed to protect the pygmy slow loris and prevent its population from decreasing in the wild. More research is needed to assess population size, distribution, and trends, and to accurately assess the threats to this species. Additionally, further conservation actions are needed to protect and manage the remaining forest inhabited by the pygmy slow loris.

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Written by Jennifer Botting, September 2019