Loris tardigradus
Creators: name: Russell A. Mittermeier
name: Anthony B. Rylands
name: Don E. Wilson
Publisher: name: Lynx Edicions
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Primates
Lorisidae
Loris
Loris tardigradus

description: 7.
Red Slender Loris
Loris tardigradus
French: Loris gréle / German: Roter Schlanklori / Spanish: Loris esbelto rojo
Other common names: Horton Plains Slender Loris (nycticeboides)
Taxonomy. Lemur tardigradus Linnaeus, 1758,
Ceylon (= Sri Lanka).
The precise type locality is unknown, but it was probably in the western lowlands of Sri Lanka. The subspecies nycticeboides was described by W. C. O. Hill in 1942 from the Horton Plains at an elevation of 1830 m in Sri Lanka’s Central Province, although there remains some dispute as to which species this taxon belongs. There is preliminary evidence for two additional subspecies in the Wet Zone of Sri Lanka. Two subspecies are recognized here.
Subspecies and Distribution.
L.t.tardigradusLinnaeus,1758—SWSriLanka(Western&Southernprovinces),fromtheoutskirtsofColombointheNtoRannaintheS,atlowerelevationsupto¢.470mabovesealevel.
L. t. nycticeboides Hill, 1942 — Sri Lanka (Central Province highlands), at elevations of 1650-2000 m above sea level.
Descriptive notes. Head—body 18-21 cm, tail vestigial; weight 85-220 g. The nominate subspecies tardigradus is the smallest of the slender loris taxa (head-body length less than 20-5 cm; weight 122-170 g). Dorsally, its pelage is red-brown with or without a dorsal stripe. The ventral hair is yellowish white with dark gray hair bases. Its preauricular hair has dark bases intergrading to its ear from its dark brown-chestnut circumocular patches, which are rounded in shape. The white interocular stripe is very narrow or absent. Its hands and feet are pink or yellowish-pink in adults. It has very large eyes and relatively small ears that are generally a woody russet color. The muzzle is long and pointed. Fur on forearms, hands, and feetis short. The toilet claw of the second digit of the foot is well developed. The “Horton Plains Slender Loris ” (L. t. nycticeboudes) 1s the most distinct of the Sri Lankan lorises. Its limbs are shorter relative to the trunk than in tardigradus, with their hindlimbs especially shortened. The skull (length 5-2 cm) is also considerably larger in all details than in the subspecies tardigradus. The fur of the Horton Plains Slender Loris is very long, soft, and thick, and it makes the animal look much larger than its body measurements would suggest (head-body 20.4-21.3 cm; weight 140-220 g); it looks superficially like a slow loris (Nycticebus). Limbs, in particular, are thickly furred toward their extremities. This furriness makes this form difficult to confuse with other slender lorises.
Habitat. Primary and some secondary wet lowland forest and tropical rainforest (tardigradus); cloud, montane, and highland evergreen forest (nycticeboides). The subspecies tardigradus is found in the wet lowland forests up to 470 m above sea level. Its habitat is heavily fragmented. It uses small twigs, lianas, and vines for movement, and it also forage on the ground. The Horton Plains Slender Loris is found in central Sri Lanka at elevations of 1800-2300 m in montane mist forests. It has been observed moving on the ground and crossing roads, and it is often seen low down in stunted vegetation. Vicinity to human populations negatively impacts the Red Slender Loris; it is rarely found in home gardens and seems to require continuous canopy to move between forest patches.
Food and Feeding. In 1905,|. Still suggested that lorises were completely insectivorous, even carnivorous. Wild Red Slender Lorises have only been seen eating animal prey. They eat insects (including moths, stick insects, dragonflies, beetles, cockroaches, and grasshoppers), lizards (Calotes, Agamidae), and geckos. They have not been seen eating birds, but the speed with which they can grasp prey and kill with a bite to the head suggests this is possible. At Masmullah Proposed Forest Reserve, lorises were found in high abundance in areas with Humboldtia laurifolia (Fabaceae), a tree that has a mutualistic relationship with ants and provides abundant food for lorises. Nothing is known of the diet of the Horton Plains Slender Loris.
Breeding. Dominant males may form partnerships with smaller beta males—coalitions to pursue estrous females. Males gather when a female is in estrus, some coming from other parts of the forest, and vocal battles are common. Gestation is 165-175 days; one twin birth in captivity occurred after 174 days. Births occur throughout the year, and singletons are more common than twins. Mothersstart to park their infants when they are about two months old, remaining near and rushing back to retrieve the infant at any sign of danger. Females have a 29-40day sexual cycle, with genital swelling and reddening at estrus. Individuals may live up to 15 years. Only one birth has been witnessed for the Horton Plains Slender Loris.
Activity patterns. The Red Slender Loris is nocturnal and arboreal. Although lorises are thought to be slow climbers, kinematic studies revealed that the nominate subspecies tardigradus can move at speeds of 1-3 m/second. In a secondary tree-fall area, Red Slender Lorises are small-branch specialists, most often moving on supports less than 5 cm in diameter and only occasionally selecting branch clusters or substrates larger than 5 cm in diameter. Overall, they do not have strong preferences with respect to branch orientation. Rapid quadrupedalism is used on arboreal supports of all diameters and orientations, but individuals have never been seen moving on the ground. The Horton Plains Slender Loris moves very much like its low-country counterpart and is also capable of incredible speed. It has been observed at low heights (2 m above the ground), and it crosses open ground. It also will occur in the highest trees available, for example, in alpine scrub at heights of 4 m.
Movements, Home range and Social organization. Virtually nothing is known about the behavior of the Horton Plains Slender Loris, so the description here refers to the subspecies tardigradus. Red Slender Lorises sleep in groups of up to five animals, most commonly a male, female, and their offspring. Some males change their sleeping site regularly and may sleep in the vicinity of a female. They engage in intense grooming sessions and social and solitary play at dawn and dusk. They communicate regularly using scent marking and loud calls. Individuals with overlapping home ranges interact throughout the night. Females have home ranges of 1-2-6-9 ha, whereas those of males are 1-4-3-4 ha. Males may affiliate with males and with more than one female. Females rarely affiliate with other females and may be aggressive toward males that attempt to follow or groom them. During the single long-term radio-tracking study on the Red Slender Loris, a single male’s home range overlapped a single female’s home range, but not all individuals in the area were caught, and more animals shared sleep sites. This, combined with promiscuous mating, implies that unimale—unifemale social pairs are not the rule for this species. Interestingly, lorises are very disturbed by white light and usually cease social behavior (e.g. partners will disperse) unless red or infrared light is used. The subspecies tardigradus utters “chitters,” “kriks,” and “zic” calls. A scream has not yet been recorded. They produce a soft whistle, barely audible to humans even when standing within 10 m of an individual. By far the most common call is the loud whistle, used to communicate location to friendly conspecifics, to warn non-group members, and to ward off encroaching males. Vocal battles are common and up to 60 calls per hour are not uncommon. The whistle is so common that it is a good indicator of loris presence or absence in a forest. At least six variations of the whistle have been described, with a potential twelve additional variants. The syllables within each call can be undulated, strangled, and short or long, and they occur in different combinations. Density estimates of lorises were 0-08-0-55 ind/ha across 15 separate sites. Loris abundance was positively associated with vines and branches providing continuous passage and trees providing a number of potential sleeping sites.
Status and Conservation. CITES Appendix II. Classified as Endangered on The IUCN Red List. The Red Slender Loris is threatened mainly by loss of habitat, and the nominate subspecies tardigradus particularly by gem mining. Individuals are regularly sold illegally in bazaars as pets, and they are valued in traditional medicine and killed because of superstitious folk beliefs. All populations are likely declining and at low levels, with as few as 1500 tardigradus in only c.3000 ha of highly fragmented forests and a critically low number of 80 nycticeboides in the Horton Plains, Sri Lanka. The subspecies tardigradus occurs in Udawalawe National Park; the sanctuaries of Attidiya-Belanwila, Kurulukele, Peak Wilderness, Udawattekele, Victoria-Randenigala-Rantambe; and forest reserves of Ingiriya, Kanneliya, Kombala-Kottawa, Oliyagankele, Polgahaivalakande, Kakanadura, Dandeniya Aparekka, and Godakawela. It can also be found in Gampola-Ambuluwela Biodiversity Park, Maimbulkanda Nature Reserve, Muthurajawela Sanctuary, Sinharaja World Heritage Site, and Masmullah Proposed Forest Reserve. The Horton Plains Slender Loris is known from the Horton Plains National Park, Hakgala Strict Nature Reserve, and Conical Hill and Bomburella forest reserves. It may also occur in the Peak Wilderness Sanctuary and Siripagama.
Bibliography. Bernede (2009), Bernede et al. (2008), Gamage et al. (2010), Goonan (1993), Goonan et al.
(1995), Groves (2001), Hill (1942b), Molur et al. (2003), Montagna & Ellis (1960), Muller et al. (1985), Napier & Napier (1967), Nekaris (2003a, 2003b, 2002/2003), Nekaris & Bearder (2007), Nekaris & Jayewardene (2003, 2004), Nekaris & Perera (2007), Nekaris & Rasmussen (2003), Nekaris & Stevens (2007), Nekaris, Liyanage & Gamage (2005), Nekaris, Pimley & Ablard (2006, 2007), Petter & Hladik (1970), Rumpler et al. (1987), Schmitt & Lemelin (2004), Schulze & Meier (1995a), Sellers (1996), Still (1905), Subramoniam (1957).
description: Published as part of Russell A. Mittermeier, Anthony B. Rylands & Don E. Wilson, 2013, Lorisidae, pp. 210-220 in Handbook of the Mammals of the World – Volume 3 Primates, Barcelona :Lynx Edicions on pages 217-218, DOI: 10.5281/zenodo.6632647