Lorises and pottos

(Lorisidae)

Class Mammalia

Order Primates

Family Lorisidae

Thumbnail description
Relatively small, fully arboreal mammals inhabiting tropical and subtropical forests; their most prominent features are marked reduction of the tail and of the second digits of the hands and feet, in association with their slow, deliberate locomotion involving powerful grasping

Size
Relatively small body size, ranging from the gray slender loris (head and body length: 8.5 in, 21.5 cm); tail length: virtually zero; body mass 9 oz (255 g) to the potto (head and body length: 15 in, 37.5 cm); tail length: 2.5 in (6.5 cm); body mass 2 lb 11 oz (1,230 g)

Number of genera, species
5 genera; 9 species

Habitat
Lorisids occur in a range of tropical and subtropical forest habitats

Conservation status
Vulnerable: 2 species; Lower Risk/Near Threatened: 2 species; Data Deficient: 1 species

Distribution
Forested areas of Africa, Asia, and Southeast Asia

Evolution and systematics

Together with the bushbabies (family Galagidae), the lorises constitute the monophyletic infraorder Lorisiformes, which is the sister group of the Lemuriformes (Malagasy lemurs). The Lorisiformes and the Lemuriformes together form a monophyletic assemblage of strepsirrhine primates, which are characterized by retention of the rhinarium (a moist area of naked skin surrounding the nostrils), by non-invasive epitheliochorial placentation and by the derived, diagnostic feature of a toothcomb containing 4 incisors and 2 canines in the lower jaw. The two subfamilies of lorisids (Lorisinae and the Perodictinae) are probably monophyletic subgroups. However, both subfamilies contain slender, small-bodied species and stocky, large-bodied species that are superficially similar but probably developed convergently.

The fossil record for lorisids is very limited. A few isolated teeth of Karanisia indicate that members of the family may have been present in Egypt during the late Eocene. A skull of the early Miocene genus Mioeuoticus from Kenya provides the earliest well-preserved evidence for the existence of the family. Fragmentary remains of the late Miocene Pronycticeboides shows that the family was present in the Indian sub-continent at least by that stage. Given this sparse fossil record, it is not possible to infer a reliable date for the origin of the lorisids.

It has been proposed, on technical grounds of priority, that the family name "Lorisidae" should be changed to "Loridae." Because the customary name "Lorisidae" has been used so widely and for such a long period of time, the International Committee on Zoological Nomenclature has recently validated Lorisidae.

Physical characteristics

Body shape varies from slender (angwantibos and slender lorises) to stocky (pottos and slow lorises), but in all species the tail is markedly reduced to virtually absent (more so in the Asiatic species than in the African species). The head is short and broad at the back; the snout is also short. The eyes are quite large and oriented obliquely upwards rather than directly forwards. The ears are medium-sized and covered with hair. The arms and legs are approximately equal in length. As in sloths, the circulatory system of the limbs is organized into a network of fine blood vessels (rete mirabile) to permit prolonged contraction of the muscles without exhaustion. In the hands and feet, the first digits

(thumb and the big toe) are strongly divergent, permitting powerful grasping, while the second finger and toe are very short to vestigial, enhancing the pincer action. All digits (fingers and toes) bear nails, although the nail on the second toe is elongated and angled obliquely upwards to form a "grooming claw."

Distribution

Slender lorises occur in Asia (India and Sri Lanka), slow lorises are widely distributed in South-East Asia, and pottos and angwantibos occur in tropical/subtropical regions of West and Central Africa.

Habitat

Lorisids occur in a range of forest habitats. They most commonly inhabit evergreen tropical rainforest, but also occur in dry, semi-deciduous forest, scrub forest, swamps, and montane forest up to middling altitudes.

Behavior

All lorisids show cryptic behavior, moving slowly and deliberately through the trees while foraging. This seems to be their primary strategy for avoidance of predation. In fact, members of this family all have low basal metabolic rates, so

they are probably constrained to slow movement for energetic reasons. All species show scent marking. They have specialized marking glands in the genital region (scrotal and vulval glands) and some of them (e.g., slender loris) perform "urine washing" in which the palms of the hands and the soles of their feet are impregnated with urine before being applied to the substrate.

Feeding ecology and diet

Members of this family typically consume a mixed diet of fruit and arthropods (mainly insects), and they may also eat small vertebrates and birds' eggs. The proportions of fruit and arthropods vary between species, with small-bodied species tending to be more insectivorous and large-bodied species tending to be more frugivorous. There is a common tendency to feed on insect species that are generally regarded as unpalatable. Some species include plant exudates (gums) in their diets, and the pygmy slow loris (Nycticebus pygmaeus) may be a specialized gum-feeder.

Reproductive biology

Most species typically have one offspring, but the pygmy slow loris often has twins. Prior to independence, the infant is typically carried around clinging to the mother's fur, and "parking" of the infant on a small branch while the mother is foraging seems to be characteristic of all species. Gestation periods are notably long relative to body size, ranging from 134 to 193 days according to species. All lorisids have non-invasive epithelichorial placentation, and are probably polygamous.

Conservation status

Four species are thought to be relatively common. No species are listed as endangered, but two are Vulnerable (Loris tardigradus and Nycticebus pygmaeus) and two are Near Threatened (Arctocebus aureus and Arctocebus calabarensis). One species, Nycticebus bengalensis, is listed as Data Deficient.

Significance to humans

Lorisids seem to be of no real significance to local human populations, although the larger-bodied species may occasionally be eaten.

Species accounts

List of Species

Gray slender loris

Loris lydekkerianus

subfamily

Lorisinae

taxonomy

Loris tardigradus lydekkerianus Cabrera, 1908. Loris tardigradus was traditionally the only species recognized in this genus, but the far more widely distributed and larger-bodied gray slender loris is now regarded as a separate species (L. lydekkerianus) containing four subspecies.

other common names

French: Loris grèle; German: Grauer Schlanklori.

physical characteristics

Relatively small, with a slender body and spindly limbs. Eyes are conspicuously large, while the snout is narrow. Fur reddish brown dorsally and grayish brown ventrally. Eyes surrounded by dark reddish brown rings. No dorsal stripe present. Head and body length: 8.5 in (21.5 cm); tail length: virtually zero. Body mass: males 9 oz (255 g); females 9 oz (255 g).

distribution

Southern India and Sri Lanka.

habitat

Deciduous forest zones.

behavior

Nocturnal and fully arboreal. Forages solitarily at night, but individual males and females have social contacts within overlapping ranges. No nests are constructed; animals typically sleep clinging to a branch among dense foliage.

feeding ecology and diet

Diet consists primarily of arthropods (mainly insects) with a supplement of fruits along with occasional eggs and small vertebrates (e.g., geckos and other lizards).

reproductive biology

Probably polygamous. Typically gives birth to a single offspring. Gestation period 168 days.

conservation status

Because of its large geographical range, this species does not seem to be immediately threatened.

significance to humans

None known.

Sunda slow loris

Nycticebus coucang

subfamily

Lorisinae

taxonomy

Nycticebus coucang (Boddaert, 1785), Malacca, Malaysia. For many years, this was the only species recognized in the genus Nycticebus. However, it became increasingly evident that a separate species should be recognized for the much smaller pygmy slow loris (Nycticebus pygmaeus), and it is also justifiable to give specific rank to the Bengal slow loris (Nycticebus bengalensis). After removal of these two species, the remaining species Nycticebus coucang contains 3 subspecies.

other common names

French: Nyticèbe; German: Plumplori.

physical characteristics

Medium-sized slow loris. Fur pale brown dorsally and buffy white ventrally. A wide brown midline stripe runs down the back. Head and body length: 12.5 in (31 cm); tail length: virtually zero. Body mass: males 1 lb 8 oz (680 g); females 1 lb 6 oz (625 g).

distribution

Malaysian Peninsula south of the Isthmus of Kra, Sumatra and nearby islands, Java, Borneo and neighboring islands.

habitat

Evergreen tropical rainforest, with a preference for forest edges.

behavior

Nocturnal and fully arboreal.

feeding ecology and diet

Feeds primarily on fruit, with a complement of arthropods (mainly insects) and some gums. Also eats eggs and small vertebrates. Reportedly concentrates on insects with a repugnant taste and/or smell.

reproductive biology

Believed to be polygamous. Typically gives birth to single offspring. Gestation period 191 days.

conservation status

Relatively common and not immediately threatened.

significance to humans

None known.

Pygmy slow loris

Nycticebus pygmaeus

subfamily

Lorisinae

taxonomy

Nycticebus pygmaeus Bonhote, 1907, Nhatrang, Vietnam. This dwarf form of the slow loris was traditionally included in the species Nycticebus coucang, but it is now recognized as a separate species. In fact, Nycticebus pygmaeus has a more limited geographical range, overlapping extensively with that of Nycticebus coucang.

other common names

English: Pygmy loris; French: Nycticèbe nain; German: Zwergplumplori.

physical characteristics

Small-bodied slow loris. Fur bright orange-brown dorsally and orange-tinted gray ventrally. Midline dorsal stripe is faint or completely lacking. Head and body length: 10 in (25.5 cm); tail length: virtually zero. Body mass: males 11 oz (310 g); females 11 oz (310 g).

distribution

East of the Mekong River in the southernmost part of China, Laos, eastern Cambodia, and Vietnam.

habitat

Evergreen tropical rainforests, with a preference for secondary growth.

behavior

Nocturnal and fully arboreal. Forages solitarily at night. Does not use nests, but sleeps clinging to branches in dense foliage.

feeding ecology and diet

Combined diet of fruit, arthropods, and gum. A habit of gouging wood with the toothcomb that has been observed in captivity suggests that this species may be a specialized gumfeeder.

reproductive biology

Gives birth to singletons or twins with approximately equal frequency. Gestation period 192 days. Mating system is not known.

conservation status

Listed as Vulnerable.

significance to humans

None known.

Calabar angwantibo

Arctocebus calabarensis

subfamily

Perodictinae

taxonomy

Arctocebus calabarensis (J. A. Smith, 1860), Old Calabar, Nigeria. Most classifications have recognized only a single species in the genus Arctocebus, but there are convincing reasons for raising the golden angwantibo to the rank of a separate species (Arctocebus aureus).

other common names

English: Golden potto; French: Arctocèbe; German: Bärenmaki.

physical characteristics

Relatively small, with a slender body. Second finger and toe even more reduced than in lorisines. Fur orange-brown dorsally and white or pale gray to buff ventrally. Head and body length: 9.5 in (24 cm); tail length: 3 in (8 cm). Body mass: males 11 oz (310 g); females 11 oz (315 g).

distribution

Cameroon and Nigeria, north of the Sanaga River and extending westward to the Niger River.

habitat

Evergreen tropical rainforests of equatorial Africa, including both primary and secondary forests.

behavior

Nocturnal and fully arboreal. Typically moves around slowly and deliberately among fine branches, and is generally cryptic. Forages solitarily, but individual males and females have social contacts through overlapping home ranges.

feeding ecology and diet

Feeds predominantly on arthropods (mainly insects) with a complement of fruit.

reproductive biology

Typically gives birth to a single infant. Gestation period 134 days. Mating system is not known.

conservation status

Listed as Near Threatened.

significance to humans

None known.

Potto

Perodicticus potto

subfamily

Perodictinae

taxonomy

Perodicticus potto (Müller, 1766), Elmina, Ghana. Three subspecies recognized. It is likely that there are several cryptic potto species that will be recognized once a thorough review has been conducted.

other common names

French: Potto de Bosman; German: Potto.

physical characteristics

Fur dark brown dorsally and paler brown ventrally. Second finger and toe even more reduced than in lorisines. There are long processes on most of the neck vertebrae and on the first two thoracic vertebrae. The shoulder region is covered by a protective scapular shield through which the vertebral spines protrude. Head and body length: 15 in (37.5 cm); tail length: 2.5 in (6.5 cm). Body mass: males 2 lb 12 oz (1,250 g); females 2 lb 11 oz (1,210 g).

distribution

Equatorial Africa, from Nigeria in the west to western regions of Uganda and Kenya in the east. Range includes Sierra Leone, Ghana, Cameroon, Equatorial Guinea, Congo-Brazzaville, and Democratic Republic of the Congo (Zaïre).

habitat

Evergreen tropical rainforests of equatorial Africa, both primary and secondary, and wooded savanna.

behavior

Nocturnal and fully arboreal. Generally cryptic, with ponderous, slow-moving locomotion. Responds to predators by presenting its upper back region, which is protected by a scapular shield and long vertebral spines. Individuals forage solitarily, but an adult male may have social contact with one or more females through range overlap. No nests are constructed; individuals simply sleep in dense foliage.

feeding ecology and diet

Feeds primarily on fruits, but complements its diet with arthropods (mainly insects) and gums. Particularly consumes insects that are generally unpalatable, such as ants.

reproductive biology

May be polygamous. Typically gives birth to a single infant. Gestation period 193 days.

conservation status

Relatively common and not immediately threatened, although it is possible that there are several potto species, some of which may be threatened.

significance to humans

None known.

False potto

Pseudopotto martini

subfamily

Perodictinae

taxonomy

Pseudopotto martini Schwartz, 1996, West Africa. This new genus and species was first recognized in 1996 on the basis of a museum skeleton of uncertain origin.

other common names

None (because of the recent discovery of this genus and species).

physical characteristics

External appearance unknown. Head and body length: unknown; tail length: unknown, but the type skeleton indicates that it is certainly longer than in the potto. Body mass: unknown.

distribution

The type specimen reportedly came from an unknown locality in equatorial West Africa, while a second specimen came from Cameroon. (Specific distribution map not available.)

habitat

Evergreen tropical rainforest.

behavior

Presumably nocturnal and fully arboreal.

feeding ecology and diet

Nothing is known.

reproductive biology

Nothing is known.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Resources

Books

Alterman, Lon, Gerald A. Doyle, and M. Kay Izard, eds. Creatures of the Dark: The Nocturnal Prosimians. New York: Plenum Press, 1995.

Bearder, Simon K. "Lorises, Bushbabies, and Tarsiers: Diverse Societies in Solitary Foragers." In Primate Societies, edited by Barbara B. Smuts, Dorothy Cheney, Robert M. Seyfarth, Richard Wrangham, and Thomas Struhsaker. Chicago: Chicago University Press, 1987.

Charles-Dominique, Pierre. Ecology and Behaviour of Nocturnal Primates. London: Duckworth, 1977.

Groves, Colin P. Primate Taxonomy. Washington, DC: Smithsonian Institute, 2001.

Jenkins, Paula D. Catalogue of Primates in the British Museum (Natural History) and Elsewhere in the British Isles. Part IV: Suborder Strepsirrhini, including the Subfossil Madagascar Lemurs and Family Tarsiidae. London: British Museum (Natural History), 1987.

Manley, Gilbert H. "Functions of the External Genital Glands of Perodicticus and Arctocebus." In Prosimian Biology, edited by Robert D. Martin, Gerald A. Doyle, and Alan C. Walker. London: Duckworth, 1974.

Martin, Robert D. Primate Origins and Evolution: A Phylogenetic Reconstruction. Princeton, NJ: Princeton University Press, 1990.

Schulze, H., and B. Meier. "Behavior of Captive Loris tardigradus nordicus: A Qualitative Description, Including some Information about Morphological Bases of Behavior." In Creatures of the Dark: The Nocturnal Prosimians, edited by Lon Alterman, Gerald A. Doyle, and M. Kay Izard. New York: Plenum Press, 1995.

Schwartz, Jeffry H., and Jeremy C. Beutel. "Species Diversity in Lorisids: A Preliminary Analysis of Arctocebus, Perodicticus, and Nycticebus." In Creatures of the Dark: The Nocturnal Prosimians, edited by Lon Alterman, Gerald A. Doyle, and M. Kay Izard. New York: Plenum Press, 1995.

Sussman, Robert W. Primate Ecology and Social Structure. Volume 1: Lorises, Lemurs and Tarsiers. Needham Heights, MA: Pearson Custom Publishing, 1999.

Periodicals

Charles-Dominique, P., and R. D. Martin. "Evolution of lorises and lemurs." Nature 227 (1970): 257–260.

Izard, M. K., and D. Rasmussen. "Reproduction in the slender loris (Loris tardigradus malabaricus)." American Journal of Primatology 8 (1985): 153–165.

Izard, M. K., K. Weisenseel, and R. Ange. "Reproduction in the slow loris (Nycticebus coucang)." American Journal of Primatology 16 (1988): 331–339.

Jurke, M. H., N. M. Czekala, and H. Fitch-Snyder. "Non-invasive detection and monitoring of estrus, pregnancy and the postpartum period in pygmy loris (Nycticebus pygmaeus) using fecal estrogen metabolites." American Journal of Primatology 41 (1997): 103–115.

Jurke, M. H., et al. "Monitoring pregnancy in twinning pygmy loris (Nycticebus pygmaeus) using fecal estrogen metabolites." American Journal of Primatology 46 (1998): 173–183.

Kadam, K. M., and M. S. Swayamprabha. "Parturition in the slender loris, Loris tardigradus lydekkerianus." Primates 21 (1980): 567–571.

Loannou, J. M. "The oestrous cycle of the potto." Journal of Reproductive Fertility 11 (1966): 455–457.

Müller, Ewald F. "Energy metabolism, thermoregulation and water budget in the slow loris (Nycticebus coucang, Boddaert, 1785)." Comparative Biochemistry and Physiolology–A 64 (1979): 109–119.

Müller, E. F., U. Nieschalk, and B. Meier. "Thermoregulation in the slender loris (Loris tardigradus)." Folia Primatology 44 (1985): 216–226.

Nekaris, K. A. I. "The spacing system of the slender loris (Loris tardigradus lydekkerianus) and its implications for slender loris social organization." American Journal of Primatology 51, Suppl. 1 (2000): 77.

Oates, John F. "The niche of the potto, Perodicticus potto." International Journal of Primatology 5 (1984): 51–61.

Ramaswami, L. S., and T. C. A. Kumar. "Reproductive cycle of the slender loris." Naturwissenschaften 49 (1962): 115–116.

Rasmussen, D. T., and K. A. I. Nekaris. "Evolutionary history of lorisiform primates." Folia Primatology 69 Supplement (1998): 250–285.

Schwartz, J. H. "Pseudopotto martini: a new genus and species of extant lorisiform primate." Anthropological Papers of the American Museum of Natural History 78 (1996): 1–14.

Schwartz, J. H., J. Shoshani, I. Tattersall, E. L. Simons, and G. F. Gunnell. "LORISIDAE Gray, 1821 and GALAGIDAE Gray, 1825 (Mammalia, Primates): Proposed conservation as the correct original spellings." Bulletin of Zoologic Nomenclature 55 (1998): 165–168.

Smith, R. J., and W. L. Jungers. "Body mass in comparative primatology." Journal of Human Evolution 32 (1997): 523–559.

Walker, A. C. "The locomotion of the lorises, with special reference to the potto." East African Wildlife Journal 7 (1969): 1–5.

Weisenseel, K. A., M. K. Izard, L. T. Nash, R. L. Ange, and P. Poorman-Allen. "A comparison of reproduction in two species of Nycticebus." Folia Primatology 69 Suppl. (1998): 321–324.

Wiens, F., and A. Zitzmann. "Predation on a wild slow loris (Nycticebus coucang) by a reticulated python (Python reticulatus)." Folia Primatology 70 (1999): 362–364.

Zhang, Y.-P., Z.-P. Chen, and L.-M. Shi. "Phylogeny of the slow lorises (genus Nycticebus): An approach using mitochondrial DNA restriction enyme analysis." International Journal of Primatology 14 (1993): 167–175.

Robert D. Martin, PhD