Lorises
Lorises
The lorises and pottos, family Lorisidae, includes nine species of Asian and African primates. Loris is a Dutch word for clown, given to these amusing creatures by European seaman who saw them. With the lemurs, these attractive little primates make up the group called prosimians, or “pre-monkeys.” All lemurs are found on the big island of Madagascar, while lorises and pottos are found in West and Central Africa, India, Sri Lanka, and Southeast Asia. Unlike the lemurs, the lorisids have little or no tail.
The quick-moving African bushbabies or galagos were formerly classified in a subfamily of the Lorisidae, the Galaginae, but are now considered by most taxonomists to comprise a separate family, the Galagidae.
Lorises and pottos are nocturnal, or active during the night. This fact keeps them from competing with the monkeys with which they share their habitat. Therefore, the monkeys are asleep when the lorisids are active. Like other prosimians, they have a reflective layer, called the tapetum lucidum, in back of the retina of the eye. This allows them to see when there is very little light. It also makes their eyes shine in the dark, like a cat’s eye.
Like the lemurs, but not like the related tarsiers, lorisids have rhinariums, which are rough-skinned, moist noses indicating that scent is very important in their lives. They mark their paths for other lorises as they move throughout their range by wetting their hands and feet in urine. They apparently prefer to stay alone in their territories except during breeding season.
Lorisids have front bottom teeth that point forward, forming a dental comb used in grooming and feeding. Underneath the tongue is a hard structure with points that are used to clean the dental comb. Lorisids can also groom their soft fur with the toilet claw. This is a special claw located on the second toe. All other fingers and toes bear flat nails. This does not
mean that they have trouble climbing, however. Their feet bear a single opposable big, or first, toe that allows them to grasp branches tightly. This grasping ability allows the lorisids to hang securely upside down, dangling from their hind feet while they eat with their hands, or perhaps just for play. The lorisids’ diet includes fruit, insects, small vertebrates, birds’ eggs, and the oozing gum of trees.
Lorisids range in size from the gray slender loris (Loris lydekkerianus ) at 9 oz (255 g) to the plump potto (Perodicticus potto ), which may reach more than 2 lb (1 kg). Though it is not known how long these primates live in the wild, they have been known to reach 12, even 14 years in captivity.
Lorises, Slow And Not So Slow
Lorises move in very deliberate fashion, with none of the free-wheeling abandon of many other primates. Moving among the branches of trees at night is serious business. They make sure that one hand is well anchored before moving the other one. They also make the movements with incredible smoothness, disturbing nothing around them. This keeps them from being seen by predators as they move through the dense tree tops. They can remain absolutely motionless for many hours at a time, a technique that is very effective in staying alive. They also have to remain silent, otherwise their high-pitched twitter can reveal their presence.
A loris’s opposable thumb is even more specialized than the thumbs of most primates. It has moved almost exactly opposite the last three fingers, and the first finger has almost disappeared. This arrangement is handy for a tight grip on the high branches in the forest canopies in which they live. Lorises are generally solitary creatures, though they may hunt in pairs or family groups.
The slender loris (Loris tardigradus ) of southern India and Sri Lanka has round eyes that look larger than they are because they are set in pear-shaped patches of dark fur on their lighter-colored triangular faces. This primate is called the slender loris because its body is much thinner than the well-rounded slow loris. It has comparatively long arms and legs.
The two species called slow lorises are indeed slow, moving very carefully and deliberately among the trees. They are plumper than the slender loris. The somewhat larger Sunda slow loris (Nycticebus coucang ) of the Southeast Asian islands Java and Borneo has a dark strip up its back and a white patch on its head and upper back. The Sunda slow loris is rapidly disappearing wherever its forest habitat is being disturbed, although it is legally protected throughout most of the countries where it lives. The pygmy slow loris (Nycticebus pygmaeus ) of Vietnam and Laos is only about 10 in (25.5 cm) long. It is round and woolly with large, close-set eyes. It is sometimes regarded as a subspecies of slow loris.
The larger potto (Perodicticus potto ) lives in equatorial Africa from Nigeria to the western regions of Uganda and Kenya. It may weigh more than 2 lb (1 kg). Its tail is visible beyond its silky fur, unlike the slow loris’s, which is not long enough to show. Also, the potto has three or four unusual skin-covered bony spines behind its neck. When threatened, the potto clings tightly to its branch, tucks in its head, and turns these spines to the attacker, which can be taken by surprise because the spines are hidden in the potto’s dense fur. If not left alone because of its spines, a potto can curl its head under its body and give a ferocious bite. In their homelands, pottos are famed for the strength of their grip.
Pottos generally live solitary lives, but the male in an area inhabited by several females keeps track of their readiness to mate by following their urine trails. After a period of getting acquainted, they may mate while hanging upside down from a branch. They have a longer gestation period than most prosimians, 193 days. This produces a baby mature enough to cling to the moving mother almost immediately after birth.
Closely related to the potto, but inhabiting the shrubs of the forests of Cameroon and Nigeria instead of the high canopy, is the angwantibo, also called the golden potto (Arctocebus calabarensis ). The angwantibo is much smaller than the potto, about 10 in (25 cm), as opposed to about 14 in (36 cm), and it lacks the neck spines. Even from birth the golden potto exhibits its skill in clinging upside down. The mother “parks” her infant upside down on a branch while she goes about her nocturnal eating. When she returns, she anchors herself around the baby, also upside down. The baby releases itself from the branch and clings right side up to her stomach. A mother angwantibo continues to nurse one infant until just before the next one is born.
Galagos Or Bushbabies
Unlike the lorises, galagos, or bushbabies as they are called because of their infant like mewing sound and sheer cuteness, reside in the lower levels of the forest. The Galagidae are known for the swiftness of their movements, which lets them capture flying insects as they zip past in midair. The commotion they make while leaping may be deliberate in that it sends disturbed insects into flight. Many jumps have been spotted as long as 15 ft (4.6 m).
Unlike most bushbabies, Allen’s bushbaby, Galago alleni, eats on the ground, where it listens for rustling insects with large, mobile ears. The ears of a galago are so important that they can fold, like an accordion, when the little animal is moving through prickly or otherwise dangerous leaves.
Galagos have longer legs compared to arms than any other primate. This allows them to make vertical leaps, from tree to tree, farther than most other primates. The tips of the fingers are broadened into soft pads that help them cling to branches. Their bushy tails are used to balance them during leaping. Galagos, like the lorises, mark their trails through the forest with urine, which they deposit directly into the bottom of one foot while standing on the other. When they hunt at night, they communicate with a variety of sounds. Then, at dawn, they gather and locate a communal sleeping hole, where they spend the daytime hours.
A mother bushbaby usually give birth to twins, which she carries in her mouth for the first two weeks. When she leaves to eat, she places them securely on a
KEY TERMS
Binocular —Using two eyes set so that their fields of vision overlap, giving the ability to perceive depth.
Dental comb —A group of lower incisor teeth on most prosimians that have moved together into a horizontal position to form a grooming tool.
Diurnal —Refers to animals that are mainly active in the daylight hours.
Opposable —If a thumb or big toe, positioned opposite the other digits, thus providing a good grip on a branch.
Rhinarium —The rough-skinned end of the snout, usually wet in prosimians, indicating that smell is important to them.
Tapetum lucidum —The special layer behind the retina of the eye of most nocturnal animals that reflects light in such a way as to amplify available light.
wide branch. A female galago, her infants, and older female offspring occupy a specific territory which they protect from outsider females. Several of these female enclaves may be located within the much larger territory of one dominant male. However, that male may lose his harem to another male the following year if he cannot put up a fierce enough fight.
Some authorities place all galagos in one genus, Galago. Others give most of them separate genera, as outlined here. The smallest galago, called the dwarf or Demidoff’s galago (Galagoides demidoff ), of East and West Africa is very much like the mouse lemur. It weighs only 2-2.5 oz (55-65 g). The largest is the brown greater bushbaby (Otolemur crassicaudatus ), which is about the size of a small cat with a very bushy tail. This species is found in South Africa, Mozambique, Malawi, and Zimbabwe inhabiting coastal, riverine, and highland forests.
The lesser or Senegal bushbaby (Galago senegalensis ) of the African rainforests is about 15 in (38 cm) long, including a 9 in (23-cm) tail, and weighs about 9-11 oz (250-315 g). It has the amazing ability to leap straight up to a height of almost 7 ft (2.1 m). On the ground, they leap like kangaroos, using both hind legs in one movement.
The forest canopy of the rainforest of Gabon and Cameroon between the Niger and Zaire Rivers is the habitat of the two species of strange little needle-clawed bushbabies— Euoticus elegantulus and E. pallidus.
Their nails are modified into sharp points for use in climbing tall tree trunks to reach gum-producing parts of the trees. As is common in prosimians, only the second toe still bears a toilet claw. These animals are reddish in color, fading to a gray underneath. They do not curl up in holes in trees or build nests.
The main protection that lorisids have from direct harm by humans is that they are so difficult to see. Thus they are not hunted as larger monkeys are. However, their forest habitat is readily degraded, and several species are threatened by this habitat loss and fragmentation.
Resources
BOOKS
Alterman, Lon, Gerald A. Doyle, and M. Kay Izard, eds. Creatures of the Dark: The Nocturnal Prosimians. New York: Plenum Press, 1995.
Kerrod, Robin. Mammals: Primates, Insect-Eaters and Baleen Whales. Encyclopedia of the Animal World series. New York: Facts on File, 1988.
Napier, J.R., and Napier, P.H. The Natural History of the Primates. Cambridge, MA: The MIT Press, 1985.
Nowak, Ronald M. Walker’s Mammals of the World. 6th ed. Baltimore: The Johns Hopkins University Press, 1999.
Peterson, Dale. The Deluge and the Ark: A Journey into Primate Worlds. Boston: Houghton Mifflin, 1989.
Preston-Mafham, Rod and Ken. Primates of the World. New York: Facts on File, 1992.
Sussman, Robert W. Primate Ecology and Social Structure. Vol. 1, Lorises, Lemurs, and Tarsiers. Needham Heights, MA: Pearson Custom Publishing, 1999.
Jean F. Blashfield