Avahis, Sifakas, and Indris: Indriidae

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AVAHIS, SIFAKAS, AND INDRIS: Indriidae

MILNE-EDWARDS'S SIFAKA (Propithecus edwardsi): SPECIES ACCOUNTS
INDRI (Indri indri): SPECIES ACCOUNTS

PHYSICAL CHARACTERISTICS

This family (also spelled Indridae) includes the indris (IN-dreez), sifakas (suh-FAH-kuhz), and the avahis (ah-VAH-heez) or woolly lemurs. Head and body length is 10.4 to 20.5 inches (26.4 to 52 centimeters). Weight ranges from 2.2 to 16.1 pounds (1 to 7.3 kilograms). The sifakas and avahis have rather long tails, while the indris have just a stump.

Indriids (members of the Indriidae family) fur color varies. Avahis can be whitish, brownish, or reddish. Indris are black and white. Sifakas are mostly black or dark brown. Fur can be woolly or silky. Contrasting fur colors occur on their backs, eyebrows, top of head, and head ruffs (a fringe of long hairs around the neck). Eye colors include golden brown, orange, and yellow. Indriid eyes are reflective, like mirrors, increasing their ability to see in dim light.

Indriids' hind limbs are longer than forelimbs. There are five fingers on each of two forefeet and five toes on each of two hind feet. All toes have nails except the second digit, or toe. This digit has a grooming (or cleaning) claw. Indriids also have a dental toothcomb, or special front teeth, used for fur cleaning.

GEOGRAPHIC RANGE

Indriids are found in Madagascar.

HABITAT

Indriids live in a wide range of environments, including original forests, disturbed forest fragments, and desert areas with spiny plants.

DIET

Indriids feed on fruit, leaves, bark, and flowers.

BEHAVIOR AND REPRODUCTION

Groups of avahis and indris have two to six members, usually an adult male and female and their young offspring. Sifakas have groups of up to ten members. Females are dominant, or in charge, in both the sifakas and indris. Little is known about avahis.

Indris and sifakas mate at three to five years old. Little is known about avahis, or woolly lemurs, although they usually have one offspring each time.

Sifakis and indris are diurnal, or active during the day. Avahis are nocturnal, or active at night.

All indriids are vertical clingers, able to climb up and down trees. They can leap long distances between trees. Indris usually stay in trees, while sifakas occasionally travel on the ground.

Scent marking and facial expressions are important means of communication for all the indriids. Vocalizations, or sounds, are also important. Among other sounds, avahis make shrill whistles, sifakas bark, honk, and making sneezing noises, and indris can sound somewhat like a loud clarinet.

INDRIIDS AND PEOPLE

Sifakas and indris are protected in some areas by taboos, or forbidden deeds. Due to their human-like hands and faces, they may be thought of as ancestor spirits, and so should not be harmed.

ONCE UPON A TIME: SLOTH LEMURS AND BABOON LEMURS

The family Indriidae has lost over half of its species in the last 1,000 years. Lost species include the sloth lemurs and the baboon lemurs. Sloth and baboon lemurs were large. Sloth lemurs might have weighed up to 441 pounds (200 kilograms). They climbed slowly and hung from tree branches. Baboon lemurs weighed up to 49 pounds (22 kilograms). They probably traveled on the ground and within trees. Sloth and baboon lemurs became extinct, not one exists anymore, anyplace, primarily due to forest destruction and human hunting.

CONSERVATION STATUS

Six indriids are considered threatened due to loss of habitat occurring from deforestation (tree removal), fire, poaching, and encroaching human populations. The golden-crowned sifaka is considered Critically Endangered, or at an extremely high risk of extinction, dying out.

MILNE-EDWARDS'S SIFAKA (Propithecus edwardsi): SPECIES ACCOUNTS

Physical characteristics: The Milne-Edwards's sifaka is black or dark brown with a large whitish patch on its lower back. Its fur is long and soft, and its face is hairless and black. Front legs are short, and hind limbs large and strong. Eye color may be orange. Males and females look alike. Adult weight is 12.3 pounds (5.6 kilograms). Head and body length is 18.9 inches (48 centimeters), with a long tail used for balancing. Sifaka males and females have scent glands for marking territory.

Geographic range: These sifakas live on the southeastern coast of Madagascar.

Habitat: Milne-Edwards's sifaka is found in moist, humid mountain rainforests.

Diet: Milne-Edwards's sifaka eats fruits, fruit seeds, leaves, and flowers.

Behavior and reproduction: The Milne-Edwards's sifaka is diurnal, or active during daylight hours. It travels by leaping and clinging onto trees. It usually feeds within large trees, but may food search on the ground. On the ground, sifakas hop on their hind legs in an upright position, holding arms above their heads for balance. At night they sleep with a social group high in the trees. Sleeping locations can change each night to avoid predators.

Social groups have up to ten members. These groups may be all male, all female, or mixed. Females are dominant, leading their group and demanding first choice of food. However, males defend the group against large raptors, such as hawks and eagles.

Sifakas are mature at four to five years old. Females may mate with several males. One infant is born every two years. Newborns weigh 4.4 ounces (125 grams). They cling to the mother's underside for their first month, then ride on her back for the next four months. Infant mortality, or death rate, is high.

Milne-Edwards's sifakas have several vocalizations, or sounds. The loud alarm barking sound warning about bird predators may last up to fifteen minutes. A short, quick "zusss" call warns of ground predators, or enemies. Quiet "moos" tell of a group's current location. Lost sifakas give a long, warbling whistle to announce where they are.

Milne-Edwards's sifakas and people: In some areas, it is forbidden by local custom to hunt sifakas because they resemble humans.

Conservation status: Though not listed as Threatened, Milne-Edwards's sifakas may become threatened due to hunting, logging, firewood use, land clearing to provide pasture for livestock, and slash-and-burn agriculture. It has so far been impossible to keep and breed this sifaka in captivity. ∎

INDRI (Indri indri): SPECIES ACCOUNTS

Physical characteristics: The indris are the largest living prosimians (or "before apes"). They weigh 13.2 to 16.5 pounds (6 to 7.5 kilograms). Head and body length is about 23.6 inches (60 centimeters). The tail is stubby.

An indri is mostly black with white areas. A black hairless face has large tufted ears and a pointed nose area. Large eyes are yellow. Body hair is long and silky. Feet have strong big toes, and long hands have strong thumbs, creating a very powerful tree branch grasp. A special throat sac enables indris to make loud sounds.

Geographic range: Indris are found in northeastern Madagascar.

Habitat: Indris live in humid moist forests from sea level to 6,000 feet (1,830 meters).

Diet: Indris eat leaves, flowers, and fruits. When these foods are hard to find, the indri uses its tooth comb to scrape tree bark and dead wood as food.

Behavior and reproduction: Indris are diurnal, moving about only in the daytime. They live in social groups of two to six members, usually a male and female pair and their young. Female indris are dominant, or in charge. However, males are responsible for defending group feeding territory, which they mark with scent glands.

Indris are arboreal, living in trees. They leap between tree trunks. Leaps can be as long as 33 feet (10 meters). Indris seldom move on the ground; when they do, they walk upright, moving forward by hopping and holding their somewhat short arms above their body. At night, before going to sleep, indris have a group grooming session.

Indris begin mating at seven to nine years old. There are two to three years between births. Only one offspring is born each time. Tiny babies cling to the mother's underside until four months of age, then begin riding on her back. Leaping practice begins at this time. By eight months of age, young move about by themselves, although they stay with the parents for about two years.

Indris sound like a clarinet, a musical instrument, early in the morning. These calls can be heard up to 2 miles (3 kilometers) away. The indris are very territorial, making shrill cries warning other groups to stay away. There are also loud howling or singing sessions by group members. These howling songs can last up to four minutes. Other sounds made by indris include hooting and barking to warn of nearby predators, and grunts and wheezes when frightened.

Indris and people: In many areas there are local taboos against people harming indris, however hunting does occur.

Conservation status: Indris are considered Endangered, facing a very high risk of extinction, due to logging, hunting, and slash-and-burn agriculture (cutting down trees and burning remnants to clear land for farming). ∎

FOR MORE INFORMATION

Books:

Dunbar, Robin, and Louise Barrett. Cousins: Our Primate Relatives. London: Dorling Kindersley, 2000.

Kavanagh, Michael. A Complete Guide to Monkeys, Apes and Other Primates. New York: The Viking Press, 1983.

Nowak, Ronald M., and John L. Paradiso. Walker's Mammals of the World. Baltimore and London: The Johns Hopkins University Press, 1983.

Sleeper, Barbara. Primates. San Francisco: Chronicle Books, 1997.

Periodicals:

Banks, Joan. "Lemurs: Living on the Edge: On the Verge of Extinction, Do Lemurs Have a Fighting Chance?" National Geographic World (January–February 2002): 12–16.

Mitchell, Meghan. "Securing Madagascar's Rare Wildlife." Science News (November 1, 1997): 287.

"Sifaka." Ranger Rick (August 1999): 37–38.