Slender loris
| Slender lorises | |
|---|---|
 | |
| Red slender loris (Loris tardigradus) | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Suborder: | Strepsirrhini |
| Family: | Lorisidae |
| Subfamily: | Lorinae |
| Genus: | Loris É. Geoffroy, 1796[2] |
| Type species | |
| Loris tardigradus É. Geoffroy, 1796 | |
| Species | |
 | |
| Loris distribution | |
| Synonyms | |
| |
The slender lorises (Loris) are two species of loris endemic to India and Sri Lanka that comprise the genus Loris. They are small, gracile strepsirrhines that weigh between 85 and 340 grams (3.0 and 12.0 oz), with the gray slender loris (L. lydekkerianus) being larger than the insular red slender loris (L. tardigradus). Slender lorises are arboreal, nocturnal primates that forage solitarily at night and congregate into gregarious groups to sleep during the day. Mothers will leave their infants alone during the night, a behaviour known as "parking", while they forage. Slender lorises maintain predominantly carnivorous diets consisting of invertebrates such as spiders, orthopterans, snails, and ants, as well as vertebrates such as lizards, frogs, and small birds. Between the two slender loris species are seven recognised subspecies, each of which has unique morphological traits such as varying pelage patterns and body proportions. The slender lorises have undergone numerous taxonomic revisions since they were first described in the 18th century.
The head of a slender loris is distinguished by the presence of large, tapetum-covered eyes that lie close together, exhibiting the lowest interocular distance of all primates. The dentition possesses the typical strepsirrhine toothcomb, which a slender loris can use for grooming itself and others. Accomplishing a similarly hygienic function is a toilet claw of the second pedal digit, which can be used to clean almost any part of the body via the slender loris' remarkable flexibility. Slender lorises have small, pincer-like hands and feet with reduced second digits that allow an individual to powerfully grip a branch for hours at a time, with the assistance of specialised blood vessels in the limbs known as retia mirabilia. The spine is characterised by an elongated shape, and sways from side-to-side as a slender loris travels across its preferred substrates of twigs, branches, and vines. Though otherwise variable, pelage patterns are unified by the presence of a thin, vertical white stripe between the eyes, as well as dark circumocular patches.
The gray slender loris is classified as a near threatened species by the International Union for Conservation of Nature, while the red slender loris is classified as endangered. Both species are listed under Appendix II by CITES. Slender lorises are threatened by poaching for the acquisition of body parts for use in traditional medicine, as well as habitat loss.
Etymology
[edit]The Comte de Buffon was the first to identify the slender lorises with the term "loris" in the 13th volume of the Histoire Naturelle, which he adopted from the Dutch language name for the animals, loeris.[3]: 134 [4] The Dutch "loeris" refers to clowns, which could be descriptive of the slender loris' apparent acrobatic capabilities or of the markings on their faces.[3]: 134 Two variants of the term "loris" were produced in the English translation of German traveller Christoph Schewitzer's 1700 publication, those being lewer and lever. These renditions of "loris" would later be used to name pottos in the form of luyaerd, meaning "sluggard", which was subsequently reapplied to slender lorises as luyaard. Another Dutch name for the slender lorises, luiste dier, meaning "slow beast", was also mentioned by Schewitzer.[5] In English, the slender lorises are alternatively known as the "Ceylon sloths".[3]: 143
In India, slender lorises are called devanga-pilli or arawe-papa in Telugu, kaadu-paapa in Kannada, kaada naramani in Tulu, and lāzāḷū-mākaḍ in Marathi. In Tamil they are known as kada papa, meaning "baby of the forest", or theivangu, meaning "the slender-bodied one". In Sri Lanka, they are known as unahapuluwa in Sinhala, which is also a term for an emaciated person. Alternatively, they are called nama-thevangu in Sinhala, which compares the vertical interocular mark on slender lorises' foreheads to those worn by worshippers of Vishnu called namam.[6]
Taxonomy
[edit]There are two valid species of slow loris:
| Common name | Scientific name and subspecies | Range | Size and ecology | IUCN status and estimated population |
|---|---|---|---|---|
| Gray slender loris
|
L. lydekkerianus A. Cabrera, 1908 Four subspecies
|
Southern India and Sri Lanka |
Size: 18–22 cm (7–9 in) long, with no tail[7] Habitat: Forest[8] Diet: Insects[9] |
NT Unknown  [8] |
| Red slender loris
|
L. tardigradus (Linnaeus, 1758) Three subspecies
|
Sri Lanka |
Size: 18–26 cm (7–10 in) long, with no tail[10] Habitat: Forest[11] Diet: Insects, as well as tree frogs, geckos, small birds, eggs, and fruit[10] |
EN 2000–2300 [11] |
Changes in taxonomy
[edit]
Both slender and slow lorises were introduced to European scientists by Dutch voyagers returning from Sri Lanka and the East Indies, which resulted in early references to such animals being unclear as to which genus was the subject of any given description.[3]: 134 Carl Linnaeus described slender lorises as Lemur tardigradus in the 1758 10th edition of Systema Naturae.[3]: 134 Although the red slender loris is the type species of Linnaeus' Lemur, the term "lemur" has since been applied to lemuroids to the exclusion of other strepsirrhines.[3]: 134 The trivial name tardigradus was adopted from Albertus Seba's description and illustrations of the red slender loris,[12] so named because it reminded him of sloths.[4] Arnout Vosmaer echoed this sentiment in 1770, which provoked a rebuttal from the Comte de Buffon, who disproved the sloth theory by presenting the slender lorises' primate traits in the posthumous 36th volume of the Histoire Naturelle.[5]
The first author to elevate Loris to generic status, thereby separating the slow and slender lorises into different species, was Pieter Boddaert in 1784,[13] although his generic name, Tardigradus, was preoccupied. As such, taxonomic priority belongs to Étienne Geoffroy Saint-Hilaire's 1796 description of Loris gracilis in the Magasin encyclopédique.[3]: 134 Geoffroy described Loris on the mistaken assumption that Linnaeus' Lemur tardigradus was a slow loris.[12] Johann Karl Wilhelm Illiger authored a competing description of slender lorises, Stenops, in 1811.[3]: 134 Expanding on Geoffroy's taxonomy, Gotthelf Fischer von Waldheim described a yellowish-brown loris as Loris ceylonicus in 1804. René Lesson later authored his own description of the red slender loris, Arachnocebus lori, in 1840. Richard Lydekker established the first definitive taxonomic distinction between the red and gray slender lorises in 1905. Believing that two gray slender loris specimens from Chennai were representatives of the typical L. gracilis form described by Geoffroy in 1796, Lydekker described the red slender loris as L. g. zeylanicus.[12] Ángel Cabrera attempted to correct Lydekker's error in 1908 by describing the gray slender loris as L. lori lydekkerianus, with the red slender loris remaining as the type of the genus.[12][14]
In 1913, Kathleen V. Ryley published a revision of the genus wherein she merged all then-extant Sri Lankan taxa into a single species, L. tardigradus, thereby returning to the Linnaean trivial name. She also elevated Cabrera's L. l. lydekkerianus subspecies to a species in its own right, which she named the Mysore slender loris (L. lydekkerianus).[15][16] Robert Charles Wroughton later described the Malabar slender loris (L. malabaricus) on account of its small size and unique pelage.[16] In 1932, the slender lorises of Sri Lanka were divided into two subspecies by William Charles Osman Hill and William Watt Addison Phillips, those being L. t. tardigradus and the novel Ceylon highland slender loris (L. t. grandis).[12][17] The following year, Hill described the northern form of the Sri Lankan gray slender lorises as the northern Ceylonese slender loris (L. t. nordicus). At that time, Hill found it necessary to revise the entire genus, as L. t. nordicus appeared to occupy an intermediate position between all then-known forms of slender lorises. As such, he described the slender lorises as comprising a single species, L. tardigradus, with five different subspecies.[12][14] He described a sixth subspecies, L. t. nyctibceboides, in 1942. Hill's monospecific taxonomy was revised in 1998 by Colin Groves, who separated the red and gray slender lorises into two different species.[12][18] A final subspecies, the northwestern red slender loris (L. t. parvus), was described by Saman Gamage et al. in 2017, who speculated that its morphological differences from the southwestern red slender loris may qualify it as an independent species, given further examination.[12]
Anatomy and physiology
[edit]
The slender lorises are small primates that are characterised by their extreme gracility and their suite of highly derived traits.[19] They can be distinguished from other lorisids by their lithe habitus, enlarged orbits, and short, pointed snouts.[3]: 135 Females are generally larger than males.[3]: 144 The gray slender loris is much larger than the red slender loris, as infant gray slender loris are about the same size as adult red slender lorises.[20] The head appears spherical[21]: 81 and the coronal suture is often asymmetrical.[3]: 143 Unlike some other strepsirrhines such as galagos, there is no supraorbital notch.[3]: 139 The snout is elongated beyond the tooth row due to the large size of the premaxillae.[21]: 186 The skull exhibits post-orbital constriction as a result of a reduced interorbital distance,[21]: 186 which is the lowest among all primates.[19] The resultant overlapping visual fields of the two forward-pointed eyes creates a sophisticated stereoscopic vision.[22] The dental formula is 2.1.3.32.1.3.3 × 2 = 36. The dentition is characterised by the presence of a toothcomb and a caniform lower anterior premolar (P1).[23] In the toothcomb, the lower incisors (I1–2) are tilted forward and are flattened laterally, with the angles of the crowns further accentuating this procumbent orientation. The lower canine (C−) is incisiform and also participates in the composition of the toothcomb. Because the canine is occupied by the toothcomb, the lower anterior premolar adopts the shape and function of the lower canine in the dentition.[21]: 235 The upper incisors (I1–2) are reduced in size due to a lack of collision with the lower incisors,[21]: 235, 247 and the inner pair are separated by a diastema[3]: 140 that allows the upper lip to attach to the gum.[21]: 394 Compared to the slow lorises, the foramen magnum is positioned further forward in the skull.[3]: 139 Slender lorises differ from all other lorisids in that their heads are not pointed in a downward direction.[21]: 186
The limbs are long and narrow, with the arms having large olecranons.[3]: 140 The intermembral index is 93.[24] The shoulders and hips permit great flexibility in the arms and legs; the hindlimbs are capable of a greater range of motion in all directions than that which is seen in simians, such that almost the entire body is accessible by a slender loris' own toe.[25] As is the case with other lorises and angwantibos, slender lorises do not have visible tails. The hands and feet are robust; both the manual and pedal second digits are reduced in size, which allows for efficient grasping of thin branches. This locomotor behaviour is further supported by the presence of retia mirabilia in the blood vessels of the limbs,[3]: 129, 132 which allow a slender loris to sustain a continuous grasp for hours at a time.[21]: 348 This grip is so strong that it can be difficult to dislodge a slender loris from its position once it has grasped a branch. Manual digit 4 is the longest in the hand, which increases the breadth of a slender loris' grasp by being positioned opposite the thumb (manual digit 1).[25] The thumb is not truly opposable, as the palmar pad at the base of the digit is stationary.[3]: 42 Pedal digit 2 possesses a grooming claw, which is typical of strepsirrhines; this is not a true claw, as it is instead a broad, compressed nail that is used for grooming and scratching,[21]: 352 which is especially important for hygienic purposes because the other nails do not extend beyond the tips of the digits.[25] The digital formula is 4>3>5>2>1.[26] The papillary ridges are prominent, especially on the hands of the forelimbs.[3]: 136 The slender lorises have elongated spinal columns that allow their spines to sway from side-to-side in a serpentine manner during arboreal locomotion.[3]: 131, 133 The spine is composed of seven cervical vertebrae, 14–15 thoracic vertebrae, eight or nine lumbar vertebrae, three sacral vertebrae, and five caudal vertebrae. The lumbar vertebrae are elongated about the central axis of the spine, and the final five or six vertebrae are fused to form the coccyx. 14–15 pairs of ribs are present.[3]: 140
The brain weighs between 4.5 and 8 g (0.16 and 0.28 oz), and there is no central sulcus.[3]: 143 The slender lorises have chestnut-coloured eyes that possess reflective tapeta lucida,[3]: 143 which is common between strepsirrhines.[21]: 458 The retina contains narrow rods and lacks cones altogether, which are traits that are associated with nocturnality.[22] Dark circumocular patches are present in all individuals, as is a white stripe that runs vertically between the eyes.[3]: 144 The slender lorises' extremely gracile appearances are partially resultant of their thinner, sparser pelages compared to the thicker coats of slow lorises.[21]: 81 They have hairless brachial glands on the inside of the arms, which emit an exudate that may play a role in olfactory communication with conspecifics (fellow members of a slender loris species) or in predator avoidance.[10] The stomach is simple and spherical in shape, and the caecum is unsacculated. Anatomists such as Anton Nuhn have described the slender lorises as possessing a veriform appendix, whereas Paul Broca considered the same mass to be part of the caecum.[3]: 141–142 The large intestine is arranged such that it is coiled into corkscrew-shaped spirals known as ansa coli.[21]: 498 The male's scrotum changes colour during rut, wherein the pigmentation adopts a reticulated pattern.[3]: 136 Females exhibit sexual swelling during oestrus.[19]
Variation
[edit]
The colour of pelages varies between species and subspecies. Climatic factors may influence the distribution of colourations, as taxa found in wetter climates tend to be more rufous, whereas those in drier climates are darker and are sometimes accompanied by a pale frosting atop the pelage.[3]: 144 The smallest slender loris subspecies is L. t. tardigradus, which weighs between 85 and 113 g (3.0 and 4.0 oz). The adult male is uniformly russet-coloured, and has a faint or absent dorsal medial stripe. The female is wood-brown with frosting on the lumbar area. Ventrally, L. t. tardigradus is buff to yellow.[3]: 145 L. t. parvus weighs between 123 and 170 g (4.3 and 6.0 oz), and has a dark, golden-brown colouration with short fur.[12] L. t. nycticeboides is short-limbed and heavily coated with earth-brown dorsal pelage that is paler over the loins and hindlimbs, and lacks frosting. Ventrally, it is ochre. On the face, the interocular stripe is bifurcated at the top. The size of this subspecies is between that of L. t. tardigradus and L. l. grandis, and its robust habitus resembles those of the slow lorises. L. l. grandis weighs between 155 and 198 g (5.5 and 7.0 oz), and is dorsally dark grey to brownish grey, while being pure white ventrally with heavy frosting over the loin area. Females and immature individuals are darker than adult males, and the extremities are more fully-coated than most other subspecies. L. l. malabaricus weighs about 170 g (6.0 oz). It is russet to wood-brown dorsally, while it is dirty white or buff on the ventral surface. The dorsal stripe is either faint or absent. L. l. nordicus is the about 240 g (8.5 oz), and is ash grey and heavily frosted on the dorsal surface and white on the ventral surface. The median dorsal stripe connects to a dark patch on the crown of the head. L. l. lydekkerianus is the largest slender loris, weighing between 283 and 340 g (10.0 and 12.0 oz), and resembling L. l. nordicus except for its lack of grey hair bases in the ventral pelage.[3]: 145–147
Distribution and habitat
[edit]
The red slender loris is only found in Sri Lanka, while the gray slender loris occurs in both Sri Lanka and India. Two of the subspecies of red slender loris differ in their habitat preference; the southwestern red slender loris favours wet lowland forests (up to 470 m (1,540 ft) above sea level) in the south western wet-zone of Sri Lanka, whereas the highland red slender loris prefers cloud, montane, and highland evergreen forests at elevations of 1,800–2,300 m (5,900–7,500 ft). The gray slender loris can be found in tropical rainforests, coastal acacia scrub forests, semi-evergreen forests, swamps, and bamboo groves up to 2,000 m (6,600 ft) above sea level.[27]
The average population density of slender lorises is about 2.4 lorises/km2, which varies between habitats. The population density in dry habitats is 3.85 lorises/km2. It is 1.21 lorises/km2 in wet habitats, 0.45 lorises/km2 in intermediate habitats, and 0.49 lorises/km2 in montane habitats. Slender lorises are found at an average height of 3.0 to 3.4 metres (9.8 to 11.2 ft) above the ground. Both species occur more frequently in unprotected forests than in protected forests, and are most commonly found in undergrowth and secondary forests, where preferred substrates are readily available for travel. Dry forest forms tend to fare better in close proximity to humans than wet forest forms; the dry forest-dwelling gray slender loris can even be found in home gardens. Additionally, the distribution of gray slender lorises is correlated with the availability of horizontal substrates such as man-made fences, whereas red slender lorises prefer vertical substrates such as vines. This could explain the absence of slender lorises in the southeast of Sri Lanka, which consists of dry forests with few horizontal substrates. Slender loris distributions and group size variations are also associated with the availability of preferred food items such as ants and orthopterans.[28]
Behaviour
[edit]Posture and locomotion
[edit]
The slender lorises are highly specialised animals, partially as a result of their inability to jump combined with their obligatorily arboreal method of locomotion. Because they cannot leap, slender lorises span gaps in their substrates using bridging postures. Although they are more efficient with clinging to and moving across thin substrates that can fit within their small, pincer-like hands and feet, they are also able to scale thick tree trunks if necessary. Throughout a night, a slender loris will travel about 1 kilometre (0.62 mi).[26] Red slender lorises exhibit quicker movements than gray slender lorises, and utilise smaller substrates for travel as a result of their reduced size.[20] Male slender lorises generally engage in more locomotor activity than females.[22]
During sleep and rest, a slender loris rolls into a ball with the head and hands tucked between the thighs while the legs grasp a branch. While the sleep and rest posture is maintained, the torso is stabilised within the fork of two branches. Before this posture is assumed, a leaf is often procured and placed in the fork to cushion the body from the hard surface of the branch, which possibly results from the lack of ischial callosities on the hindquarters. When frightened, a slender loris will stand up on a branch bipedally with its elbows flexed at the height of the sternum.[25] When seized by a human, red slender lorises assume a defensive posture wherein they raise their arms above their heads and sway their bodies from side-to-side, possibly to mimic the behaviour of Indian cobras (Naja naja).[10]
Social structure
[edit]
The slender lorises spend about 50% of their waking hours in proximity to conspecifics. Social behaviours can include association while feeding, play wrestling, and interaction with infants.[20] Female slender lorises generally have exclusive home ranges, whereas males' may overlap multiple females'.[27] The home ranges of females average 1.6 hectares (4.0 acres) in size,[19] and can be as small as a single tree. Home ranges are clustered together into larger socioterritorial units known as colonies.[22] Slender lorises form sleeping groups of two to seven individuals. They are the only lorisids to sleep in social groups larger than a mother-infant pair. Such groups congregate about 30 minute before dawn, during which time participants will engage in a gregarious period of frequent social interactions with conspecifics. They then disperse at dusk.[19] Adult slender lorises typically hunt separately during the night,[27] although they will sometimes do so in pairs.[24]
Communication
[edit]Several vocalisations can be produced by slender lorises. A defensive screech indicates stress, and is composed of a high-intensity chitter. Alternatively, a slender loris can produce a low "pant-growl" as part of a defensive display, which may be accompanied by bluff attacks. A rhythmic chitter is also used in defensive contexts, such as when rebuffing a conspecific if play behaviours become too rough. A typically sharp, monosyllabic territorial whistle is produced to threaten others or to defend one's territory. While pursuing females in oestrus, males utter a low, hissing appeasement call, which can also be produced when rejected by the female. Females reject male suitors with a monosyllabic chitter of low clicking or smacking sounds. Infants utter a "zic" call consisting of a short monosyllabic click to indicate discomfort when being groomed or when they exhibit fear in unfamiliar situations such as falling from their mothers. During play wrestling, participants produce a low, non-tonal sniffing-sound. A short, low, monosyllabic whistle or squeak is used for contacting conspecifics in an affiliative context. When seized by a human, slender lorises produce a "scream" of long, repeated loud calls interrupted by inhalations. Slender lorises may also produce ultrasonic vocalisations. Non-vocal auditory signals are produced by deliberately rattling twigs; in northern Ceylonese slender lorises, twig-rattling can be used in dominance displays.[29] A subspecies may tend to emit some vocalisations more than others, and can also produce unique variants of these vocalisations. Such variants could assist with mate identification through intraspecific recognition.[20]
Olfaction is an important aspect of the territorial and reproductive behaviour of slender lorises, especially regarding urine marking. Communicative odours are acquired by sniffing and through contact with the observer's rhinarium. Soluble, odorous substances are transported to the vomeronasal organ via movement of the tongue or along the median furrow of the rhinarium. Slender lorises often travel with their nose pressed to the surfaces of substrates as an exploratory behaviour in new settings and in relation to urine marks left by other lorises. Conspecifics can be directly sniffed as part of olfactory communication, which often involves a male smelling the genital region of a female.[22]
Visual communication can be accomplished through a small repertoire of facial expressions. When perceiving unfamiliar stimuli, slender lorises exposure fur gaps in the corners of their mouths. Social distress prompts the drawing down of the ears to the side of the head. In severely distressing situations, the ears are laid backward against the head, which is also done while hunting. Stressful situations may also cause the cleft of the lip to become straight, whereas it is s-shaped when a loris is calm. Visual communication is also performed using body language; sharp, abrupt movements are indicative of an aggressive temperament, while content animals move swiftly and noiselessly. Suspensory locomotion beneath substrates indicates sexual receptiveness in females, as this prompts male attempts at mounting. To invite social grooming, the arm is presented forward, exposing the brachial scent gland.[22]
Diet
[edit]The slender lorises are carnivorous insectivores whose favoured prey includes ants, orthopterans,[28] and spiders. These are food items that are not sought after by potential competitors such as carnivorous reptiles, which places slender lorises in an ecological niche typically belonging to predatory and parasitic invertebrates.[30] Slender lorises visually track their prey from a distance of up to 2 metres (6 ft 7 in) prior to attacking, and maintain contact with their supportive substrate with two or three limbs while pouncing. As it strikes evasive prey such as orthopterans or moths, a slender loris compresses its ears and coils its hindlimbs in a manner akin to a pouncing house cat. This predatory pounce consists of a set of fixed behaviours initiated in response to optical stimuli, insofar as the full sequence of reaching, snatching, and the opening of the mouth are performed regardless of whether or not any prey has been seized.[22] The hands or teeth are used to process captured prey prior to consumption, although small ants are eaten whole. The slender lorises ingest large amounts of toxic secondary metabolites from their prey.[31] In addition to insects, they also eat frogs, lizards, and snails. Slender lorises also consume some non-prey food items, including shoots, young leaves, and hard-rind fruits.[24] In Sri Lanka, they have been observed to consume the flowers of Cassia roxburghii.[20] The slender lorises have slower metabolisms than what would be expected for animals of their size.[10]
Reproduction
[edit]
Courtship involves pursuit by multiple males of a single female in oestrus. Males produce a copulatory plug in females after a successful mating, which the female sometimes removes and eats.[19] Slender lorises undergo long gestation periods for animals of their size,[32] and the gestation period is longer in red slender lorises than gray slender lorises. The two species are not capable of hybridising.[20] Mating and births occur throughout the year; slender lorises were previously believed to be seasonal breeders, however this observed pattern may have been the result of altered behaviours in captive settings. Singleton, twin, and triplet births occur, without a subspecific correlation. The reproductive output of slender lorises is high, being about four infants per year, which may be explained by a combination of paternal investment and the production of milk with high energy content. Slender loris milk is anomalously nutritious compared to the typically poor-quality milk produced by most other primate species, which may allow for longer "parking" periods during which the mother is not required to attend to her offspring.[19] Infants can be successfully born in a headfirst or in a breech position.[24]
After birth, infants are immediately able to open their eyes and grip their mother's fur. During the first four weeks of an infant's life, it is carried on its mother's back while its father visits to groom both his mate and his offspring. Between four weeks and two months after birth, the infant begins to be parked during the night while the mother forages. During this parking period, gray slender loris fathers may visit their parked infants to play with them, whereas mothers rarely return to parked infants before dawn. An infant can move up to 20 metres (66 ft) from its parking location on its own throughout the night, and will summon its mother before dawn using the "zic" vocalisation. As infants age, their mothers retrieve them with less urgency. The father participates in the socialisation of the infant by comprising up to 40% of his infant's activity budget, which is a significantly higher degree of direct paternal care than is demonstrated by other lorisids. Infant slender lorises may also receive paternal care from males other than their fathers, especially those in their sleeping groups. This phenomenon may be related to the promiscuous mating of female slender lorises wherein intense sperm competition may confuse paternity, thereby resulting in affiliative male investment in an infant. Parent-offspring interactions often involve direct contact in the form of grooming and tolerance of infant play behaviours to an abnormal degree for nocturnal primates, as such patterns of parental behaviour are typically seen in diurnal species. Paternal care of infants is reduced in the red slender loris when compared to the gray slender loris; a captive study found there to be no interest demonstrated by a red slender loris father in his offspring.[19] Slender loris mothers are known to care for infants other than their own.[24] In captive settings, red slender loris mothers that experience stress commit infanticide against their own infants.[19] The average lifespan of a slender loris is 15 years.[24] In captivity, gray slender lorises can live as long as 20 years.[33]
Conservation status
[edit]Both species of slender loris are threatened by poaching, which can be motivated by some indigenous beliefs systems, such as those that hold that the body parts of slender lorises are magically significant.[11][34] The eyes of slender lorises are prized in some Sri Lankan traditional medical practices, and gray slender loris body parts can be marketed as cure-all medicines.[8] Slender loris vocalisations are believed by some Sri Lankans to be ill omens, resulting in the animals being stoned to death to ward off such superstitiously portended misfortune.[28] Slender lorises are also threatened the exotic pet trade, and are smuggled to circumvent restrictions on their trafficking.[35] Anthropogenic causes of accidental death include collision with motor vehicles and electrocution from contact with uninsulated wires.[11]
Habitat loss may pose the greatest threat to the survival of slender lorises.[28] The development of major cities for residential and commercial usage is one cause of habitat loss,[11] although some populations of gray slender loris can survive in urban areas such as Bengaluru, given sufficient tree coverage.[36] Other causes of habitat destruction include the unsustainable exploitation of forests for resources such as firewood and for agricultural expansion for both smallholder and industrial purposes.[11] Forest fires also result in the destruction of slender loris habitats.[8] A 2015 survey of the Hakgala Strict Nature Reserve found that only 25% of the habitats in the protected area was suitable for habitation by slender lorises, complicating conservation efforts.[11]
The International Union for the Conservation of Nature lists the red slender loris as an endangered species[11] and the gray slender loris as near threatened.[8] Both species are listed under Appendix II by CITES.[1] In India, gray slender lorises are assigned Schedule I by the Wild Life (Protection) Act, 1972, affording them the highest level of legal protection.[37] The Kadavur Slender Loris Wildlife Sanctuary in Tamil Nadu was declared India's first slender loris sanctuary in 2022.[38]
References
[edit]- 1 2 "Checklist of CITES Species". CITES. UNEP-WCMC. Retrieved 18 March 2015.
- ↑ Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Baltimore: Johns Hopkins University Press. p. 122. ISBN 0-801-88221-4. OCLC 62265494.
- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Hill, W.C.O. (1953). "Family I. Lorisidae". Primates: Comparative Anatomy and Taxonomy. Edinburgh: Edinburgh University Press. pp. 134, 143.
- 1 2 Buffon, G.L. (1765). "Le Loris". Histoire naturelle, générale et particuliére. Tome 13, avec la description du Cabinet du roy (in French). Paris: Imprimerie royale. pp. 210, 212. Retrieved 13 August 2026.
- 1 2 Hill, W.C.O. (May 1953). "Early records of the Slender Loris and its allies". Proceedings of the Zoological Society of London. 123 (1): 43–47 [43–45]. doi:10.1111/j.1096-3642.1953.tb00153.x.
- ↑ Schulze, H. (3 February 2004). "Table 3: vernacular names" (PDF). Loris and potto conservation database. p. 1. Retrieved 15 August 2026.
- ↑ Menon, Vivek (2023). "Grey Slender Loris". Indian Mammals: A Field Guide (4th ed.). Hachette India. ISBN 978-93-93701-90-9.
- 1 2 3 4 5 Dittus, W.; Singh, M.; Gamage, S. N.; Kumara, H. N.; Kumar, A.; Nekaris, K. A. I. (2022) [amended version of 2020 assessment]. "Loris lydekkerianus". IUCN Red List of Threatened Species. 2022 e.T44722A217741551. doi:10.2305/IUCN.UK.2022-1.RLTS.T44722A217741551.en.
- ↑ Nishimura, Abi (2012). "Loris lydekkerianus". Animal Diversity Web. University of Michigan. Retrieved June 25, 2023.
- 1 2 3 4 5 McGuinness, Rory (2011). "Loris tardigradus". Animal Diversity Web. University of Michigan. Retrieved June 25, 2023.
- 1 2 3 4 5 6 7 8 Gamage, S. N.; Nekaris, K. A. I.; Rudran, R. (2022) [amended version of 2020 assessment]. "Loris tardigradus". IUCN Red List of Threatened Species. 2022 e.T12375A217756381. doi:10.2305/IUCN.UK.2022-1.RLTS.T12375A217756381.en.
- 1 2 3 4 5 6 7 8 9 Gamage, S.N.; Groves, C.P.; Marikar, F.M.M.T.; Turner, C.S.; Padmalal, K.U.K.G.; Kotagama, S.W. (2017). "The Taxonomy, Distribution, and Conservation Status of the Slender Loris (Primates, Lorisidae: Loris) in Sri Lanka". Primate Conservation. 31: 83–106 [84, 98–99].
- ↑ Stone, W.; Rehn, J.A.G. (1902). "A Collection of Mammals from Sumatra, with a Review of the Genera Nycticebus and Tragulus". Proceedings of the Academy of Natural Sciences of Philadelphia. 54 (1): 127–142 [137]. ISSN 0097-3157.
- 1 2 Hill, W.C.O. (1933). "A Monograph on the Genus Loris". Spolia Zeylanica. 18: 89–132 [91, 93].
- ↑ Ryley, K.V. (1913). "Bombay Natural Historical Society's Mammal Survey of India, Report No. 9". The journal of the Bombay Natural History Society. 22: 283–295 [285]. Retrieved 17 August 2026.
- 1 2 Wroughton, R.C. (1917). "Scientific Results from the Mammal Survey, No. 15". The journal of the Bombay Natural History Society. 25: 40–51 [45–46]. Retrieved 17 August 2026.
- ↑ Hill, W.C.O.; Philips, W.W.A. (1932). "A New Race of Slender Loris from the Highlands of Ceylon". Spolia Zeylanica. 17: 109–122 [109–111].
- ↑ Groves, C. (1998). "Systematics of tarsiers and lorises". Primates. 39 (1): 13–27 [22]. doi:10.1007/BF02557740.
- 1 2 3 4 5 6 7 8 9 Nekaris, K.A.I. (8 February 2003). "Observations of Mating, Birthing and Parental Behaviour in Three Subspecies of Slender Loris (Loris tardigradus and Loris lydekkerianus ) in India and Sri Lanka". Folia Primatologica. 74 (5–6): 312–336 [312–313, 318–326, 329–332]. doi:10.1159/000073317.
- 1 2 3 4 5 6 Nekaris, K.A.I.; Jayewardene, J. (2003). "Pilot Study and Conservation Status of the Slender Loris (Loris tardigradus and L. lydekkerianus) in Sri Lanka". Primate Conservation. 19: 83–90 [85–86].
- 1 2 3 4 5 6 7 8 9 10 11 12 Ankel-Simons, F. (2007). Primate Anatomy: An Introduction (3rd ed.). London: Elsevier Science & Technology. pp. 81, 185–186, 235, 247, 348, 352. ISBN 978-0-12-372576-9. Retrieved 4 August 2026.
- 1 2 3 4 5 6 7 Schulze, H.; Meier, B. (1995). "Behavior of Captive Loris Tardigradus Nordicus: A Qualitative Description, Including Some Information about Morphological Bases of Behavior". In Alterman, L.; Doyle, G.A.; Izard, M.K. (eds.). Creatures of the Dark: The Nocturnal Prosimians (1 ed.). New York: Springer. pp. 222, 225–227, 232, 237. ISBN 978-1-4757-2405-9.
- ↑ Schwartz, J.H. (1974). "Premolar loss in primates: a re-investigation". In Martin, R.D.; Doyle, G.O.; Walker, A.C. (eds.). Prosimian biology: proceedings of a meeting of the Research Seminar in Archaeology and Related Subjects held at the Institute of Archaeology, London University. University of Pittsburgh Press. p. 628. ISBN 0-8229-1115-9.
- 1 2 3 4 5 6 Rowe, N. (1996). The Pictorial Guide to the Living Primates. New York: Pogonias Press. p. 232. ISBN 0-9648825-1-5.
- 1 2 3 4 Subramoniam, S. (1957). "Some Observations on the Habits of the Slender Loris, Loris tardigradus (Linnaeus)". Journal of the Bombay Natural History Society. 54: 387–394 [389–392].
- 1 2 Nekaris, K.A.I. (10 September 2014). "Extreme primates: Ecology and evolution of Asian lorises". Evolutionary Anthropology: Issues, News, and Reviews. 23 (5): 177–187 [177, 179–180]. doi:10.1002/evan.21425.
- 1 2 3 Nekaris, Anna (2013). "Family Lorisidae: Angwantibos, pottos and lorises". In Mittermeier, Russell A.; Rylands, Anthony B.; Wilson, Don E. (eds.). Handbook of the Mammals of the World. Volume 3. Primates. Barcelona: Lynx Edicions. pp. 210–235. ISBN 978-84-96553-89-7.
- 1 2 3 4 Nekaris, K.A.I.; Jayewardene, J. (April 2004). "Survey of the slender loris (Primates, Lorisidae Gray, 1821: Loris tardigradus Linnaeus, 1758 and Loris lydekkerianus Cabrera, 1908) in Sri Lanka". Journal of Zoology. 262 (4): 327–338 [327, 331–332, 336–337]. doi:10.1017/S0952836903004710.
- ↑ Schulze, H. (10 September 2003). "Acoustic communication in Northern Ceylonese slender lorises (Loris tardigradus nordicus) and some information about vocalization by other forms or species of Lorisidae". Loris and potto conservation database. Retrieved 6 September 2026.
- ↑ Bourlière, F. (1974). "How to remain a prosimian in a simian world". In Martin, R.D.; Doyle, G.O.; Walker, A.C. (eds.). Prosimian biology: proceedings of a meeting of the Research Seminar in Archaeology and Related Subjects held at the Institute of Archaeology, London University. University of Pittsburgh Press. p. 19. ISBN 0-8229-1115-9.
- ↑ Nekaris, K.A.I. (September 2005). "Foraging behaviour of the slender loris (Loris lydekkerianus lydekkerianus): implications for theories of primate origins". Journal of Human Evolution. 49 (3): 289–300 [290–291, 293–264]. doi:10.1016/j.jhevol.2005.04.004.
- ↑ Hill, W.C.O. (13 April 1935). "Retinoscopy of Loris". Nature. 135 (3415): 584. doi:10.1038/135584a0.
- ↑ DiCesare, Maria (26 March 2023). "Gray Slender Loris, Loris lydekkerianus - New England Primate Conservancy". neprimateconservancy.org. New England Primate Conservancy. Archived from the original on 12 May 2026. Retrieved 23 September 2026.
- ↑ Raviprakash, Navaneeth (2022). "Medicine, black magic, and supernatural beings: Cultural rituals as a significant threat to slender lorises in India". ResearchGate. Retrieved 9 December 2024.
- ↑ "Men arrested hiding loris in underwear at Delhi airport". BBC News. 10 September 2012.
- ↑ Soumya, Elizabeth (2015-07-31). "The night-time hunt for the secretive urban slender loris of Bangalore". The Guardian. ISSN 0261-3077. Retrieved 2025-01-17.
- ↑ "Slender Loris". WWF India. WWF. Archived from the original on 10 July 2022.
- ↑ "Tamil Nadu notifies India's first slender loris sanctuary". The Hindu. 12 October 2022. Retrieved 22 September 2026.
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