Pygmy Lorises were deemed a distinct genus (Xanthonycticebus) from other Slow Loris taxa (Nycticebus) on the basis of have diverged approximately 11 million years ago, as well as traits including regularly giving birth to twins, having black naked ears, and a smaller skull length than Nycticebus (Nekaris and Nijman, 2022; Blair et al., 2023). Pygmy lorises are relatively small (360-580 g); black nose; the fur on the crown patch of the head is orangish to light brown and is diffuse to ears with eye patches rather than sharply forked. Southern Pygmy Lorises are distinct from Northern Pygmy Lorises on the basis of a skull (55 mm or less) and mandible (35 mm or less) length larger than intermedius, resulting in a longer “dog-like” muzzle; pelage is comprised of shorter hairs, and there is less distinct coat colour change through the seasons (Blair et al., 2023).  There is no evidence of hybridization, either in the wild or in museum specimens, between N. bengalensis and X. pygmaeus from localities where the two are sympatric.

Xanthonycticebus pygmaeus is listed as Endangered as 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 is currently undergoing a decline by at least 50% over a three generation (24 year) period, and that the decline will continue at the same rate for the next three generations. Population reduction is due primarily to hunting for pet trade, food, and ‘medicinal’ purposes in much of its distribution range, resulting in drastic declines that are reflected in higher prices in markets and reduced numbers available. The species is increasingly rarely encountered in biodiversity assessments. In addition, the species has also been impacted by and continues to be impacted by habitat loss from human settlements and agriculture especially cashew plantations, corn and rice paddies.

This species is found in mainland Southeast Asia east of the Mekong River in Eastern Cambodia, in Viet Nam as far north as far north as the Hai Van Pass in Quang Nam Province, and historically south to the vicinity of Ho Chi Minh City and southern Laos PDR. The western limit of distribution in Cambodia is uncertain, but it appears to be absent or at least naturally very scarce in the extreme west of the Mekong plain.

In Viet Nam, researchers have concluded that wild populations are in major decline (Fitch-Snyder and Vu 2002, Streicher 2004). In South Viet Nam in 2013, 0.48 individuals/km were recorded and 0.41-0.44 individuals/km in 2014 (Blair, unpublished data). Surveys carried out in Central Viet Nam in 2015 at the boundary between the two pygmy loris species found low densities of Xanthonycticebus, with no animals observed in 20 km at Bach Ma National Park, and 0.19 ind./km at Son Tra Nature Reserve (Blair, unpublished data). The species has also been observed in Cat Tien National Park and Vinh Cuu Biosphere Reserve, which are both part of the Dong Nai Biosphere Reserve (Kenyon et al. 2014).

In Lao PDR, Duckworth (1994) recorded the species in Xe Namnoy (0.10–0.22 animals/km) (Duckworth 1994, Evans 2000). The species is reported to be widespread in forested areas in Lao PDR, where exploitation of lorises is lower than in neighbouring Viet Nam, but with no surveys done in over 25 years, it is essential that population surveys are carried out.

In Cambodia in 2009, the species was encountered in Seima Protection Forest (0.40-0.41 individuals/km) and in Phnom Prich Wildlife Sanctuary (0.10-0.13 individuals/km) but were absent from Mondulkiri Protected Forest in 34 km of surveys (Starr et al. 2010). In Veun Sai-Siem Pang National Park, Southern Pygmy Lorises were by far the most hunted of any primate, with slingshots, crossbows and hands used to capture them. This use was by far more for medicines; the species has been targeted for ten years or more, with pet use being limited (McGrath and Behie 2021).

It is suspected that the species has undergone a >50% population decline in the last three generations (c. 21-24 years) and that it will continue to experience >50% population decline in the coming three generations. Historical population decline is suspected based on the information summarised above and elsewhere in this profile. For example, according to Global Forest Watch, since 2001, the species has lost 28% of habitat in its broadest geographic range. Combined with continual and heavy hunting, with the species being more sought after than other primate taxa for its use in over 100 traditional medicines, the species is considered to have lost 50% of its population. Future population declines are suspected on the basis that the threats facing this species continue.

This species has been sighted in a wide variety of habitats, including primary evergreen and semi-evergreen forest, forest on limestone, secondary and highly degraded habitats, and bamboo thickets (Ratajszczak 1998, Streicher 2004). It is found up to 1,500 m (MacKinnon and MacKinnon 1987).

The social organisation of this species involves a single male sharing a range with usually one but possibly two females and their dependent offspring. Based on a radio tracking study of wild animals in Cambodia, average home range sizes for 22 ha in adult males and 12 ha in adult females. Animals primarily slept in thick vegetation high in the canopy at heights of 8.5 m (Starr et al. 2011), the same height observed to be used by reintroduced Southern Pygmy Lorises in Viet Nam (Kenyon et al. 2014).

X. pygmaeus is nocturnal and forages alone or in groups of up to four individuals (Starr and Nekaris 2013). In a wild study using radio tracking, of 168 feeding bouts, Starr and Nekaris (2013) found that the species ate mainly exudates in both the cool and warm season. In the warm season, this was followed by fruits, nectar, bamboo and arthropods, whereas in the cool season, gums were supplemented with arthropods, bamboo, fungi and vertebrates. An examination of faeces broadened the diet, including plant parts, small‐sized arthropods (primarily Coleoptera and Lepidoptera), reptile scales, animal bones (bats), and animal hairs.

In Cambodia, wild Southern Pygmy Lorises gave birth to twins (Starr et al. 2012).

In Viet Nam, the Southern Pygmy Loris is heavily exploited for traditional medicine as well as for the pet trade (Nekaris and Nijman 2007), including international trade, at levels that are not sustainable; many people also consume this species for food (Streicher 2004). Some hunting involves the use of elaborate traps, as well as snares. Ratajszczak (1998) mentioned that hundreds of individuals of this species were being traded in markets, a number that has declined dramatically, suggesting also a wild decline.

In Lao PDR, habitat loss, due to agriculture (cashew plantations, corn, rice paddies etc.), and human settlement, may be resulting in localized declines.

Pygmy Lorises are the most common loris species in international pet trade, and it is unclear from which countries these animals originate, and it is possible that some “breeders” try to breed the Southern and Northern species together, leading to non-fertile hybrids. Breeders in Japan expressed a greater desire for the Northern over the Southern species (Nekaris, unpublished data). Pygmy Lorises of unknown species have, however, been introduced into non-native countries including Taiwan, Singapore and Thailand, causing potential problems for other non-native Slow Loris populations. Pygmy Lorises are the most commonly seen primates on illegal Internet trade and in Japanese pet shops (Nekaris and Starr 2015, Musing et al. 2015).
 
Lack of law enforcement further threatens Pygmy Loris species across their range (Starr et al. 2010, Nijman et al. 2014).

The species is hunted for the pet trade, for traditional medicine, photo props, food, and various other purposes (Thạch et al. 2018). The intensity of the trade has increased over the years, which is reflected in the decrease in volumes of the trade due to impacts on the wild population as well as increase in market value of the depleted stocks.

In Cambodia, the body parts of X. pygmaeus are generally sold and used for “medicinal” purposes (Nekaris et al. 2010, Starr et al. 2010). They are believed to treat more than 100 diseases, including to regain strength after childbirth, stomach problems, healing wounds and broken bones, and in the treatment of sexually transmitted diseases. Their market value has more than doubled in the last 15 years, pointing towards reduced numbers in the wild (Starr et al. 2010). High levels of exploitation for illegal wildlife trade in Cambodia appear to be a major factor in low abundances of X. pygmaeus (Nekaris et al. 2010).

In Viet Nam this species is protected at the highest possible level (Appendix IB, Decree 32, 2006); and in Cambodia it is listed on the Ministry of Forestry and Fisheries Species List as prohibited to hunt from 08 January 1994. In Lao PDR, the species is protected by the Wildlife and Aquatic Law (2007) that classifies lorises under the ‘prohibited’ category (Nekaris and Starr 2015). The species has been transferred from Appendix II to Appendix I of CITES (Nekaris and Nijman 2007). There is a need for close monitoring of harvesting rates of this species. 

Pygmy Lorises are represented in at least 50 captive collections, where they are a ‘red light’ species’ due to high inbreeding and low breeding potential (Fuller et al. 2014) and it is essential to know whether or not the captive population consists of Northern or Southern species or hybrids. Genetic work is currently underway to understand which species are held in zoological collections. The species is reported in several protected areas, but these reports need to be ground-sourced with systematic surveys (Nekaris et al. 2008).

Researchers have attempted to bring attention to and mitigate the illegal online trade in Pygmy Lorises, which is particularly prevalent in Japan and Eastern Europe (Musing and Nekaris, 2015). Ongoing campaigns combat the exploitation of Pygmy Lorises in illegal online videos (Nekaris et al. 2013, 2015).

This species has been the subject of many releases of confiscated individuals in Viet Nam and Cambodia, both monitored and unmonitored, often being unsuccessful (Streicher 2004). New strategies for release have been developed, however, with the number of successful releases on the increase; a standardised best practice for release is beginning to be recognised (Kenyon et al. 2014). The Dao Tien Endangered Primate Species Centre has not only been releasing Southern Pygmy Lorises and following releasees, but also has engaged in a number of structured conservation outreach programmes, including an onsite education centre (Cardinal et al. 2020).