There are 11 species in 3 genera in the family Indriidae. The most diverse group are the sifakas (Propithecus), with 7 species. There are also 3 species of woolly lemurs (Avahi) and 1 species of indri (Indri). As in other lemuroid families, species diversity in Indriidae has increased substantially in recent years, going from 5 species recognized in 1991 to 11 in 2005. (Nowak, 1991; Wilson and Reeder, 2005)
Indriidae includes 5 recently extinct genera, representing 7 species. These species became extinct between 500 and 1,000 years ago. The extinctions of all of these species are thought to be directly related to environmental disruptions and hunting by humans soon after their immigration and expansion on Madagascar. (Nowak, 1991)
Indriids are found in forests and scrublands throughout Madagascar. Species are found in rainforests and deciduous and evergreen forests, typically in forests with large, mature trees. (Mittermeier, et al., 2006; Nowak, 1991; Tattersal, 1982)
Indriids are morphologically diverse, from indris, the largest living strepsirhine species at up to 10 kg, to 1 kg woolly lemurs. Indris have only a stump of a tail and silky fur, while other indriids have long tails. Woolly lemurs have thick, woolly fur and small ears almost concealed in the fur of their head. Sifakas have long, thick fur dorsally which becomes sparse on their underside. They lack fur on the face. Pelage color varies considerably among species, from striking black and whites to browns and yellows. Their faces are somewhat shorter than lemurs and the legs are about 1/3 longer than the arms. The last 4 digits of the feet are joined together with flaps of skin and they act as a single unit in opposing the first toe. Females have a single pair of mammae, a baculum is present in males, and the dental formula is: I 2/2, C 1/0, PM 2/2, M 3/3. Sometimes the dental formula is interpreted as: I 2/1, C 1/1, PM 2/2, M 3/3. The lower toothcomb is made up of 4 teeth, rather than 6 as in lemurs. There is no recognized sexual dimorphism. (Nowak, 1991)
There is relatively little known about indriid mating systems. Males in at least some sifaka species become aggressive in breeding seasons, with fights between males sometimes resulting in serious injuries. Adult males may also exhibit "roaming" behavior during the mating season and competing for access to females. Females allow mating only by males that become dominant during the breeding season. (Mittermeier, et al., 2006; Nowak, 1991)
Single young are born to all indriid species at intervals of 1 to 3 years. Gestation periods are from 130 to 150 days and weaning occurs at up to 180 days after birth. Births are generally seasonal. Sexual maturity occurs at up to 36 months old. (Mittermeier, et al., 2006; Nowak, 1991)
Females care for, nurse, and protect their young in small family groups. Males in family groups may also directly or indirectly care for young, but there is little information on parental investment in the literature. Males are most often responsible for territorial defense, which may impact resources available to females and their dependent offspring. Young may also remain part of family groups for extended periods. (Mittermeier, et al., 2006; Nowak, 1991)
Indriids generally live in small groups made up of one or several females, one or several males, and dependent young. Groups are generally territorial and, although females and young are most frequently dominant over males, males are responsible for territorial defense. Group life is generally described as peaceful, except during the breeding season in some species, where male-male aggression becomes common. (Mittermeier, et al., 2006; Nowak, 1991)
Indris and sifakas are diurnal, while avahis are nocturnal. Indriid species are fairly sedentary, with groups moving 300 to 1100 meters per day. Home ranges often overlap and are from to 1 to 18 hectares in size. (Mittermeier, et al., 2006; Nowak, 1991)
Indriid species are all characterized as "vertical clingers and leapers." Indriids typically hold themselves vertically in trees and are capable of impressive leaps of up to 10 meters. They may also suspend themselves during feeding. Also unique to this group is bipedal leaping on the ground, especially in indris and sifakas, in which they jump on their two rear feet while holding the arms above their heads or in front of their bodies. (Mittermeier, et al., 2006; Nowak, 1991)
Like other primates, indriids rely heavily on vision for finding food, navigating, and in communication. Indriids have excellent, binocular vision. Woolly lemurs are nocturnal and have excellent vision in low light. Vocalizations play an important role in social communication as well. Indris sing melodious songs that can be heard up to 2 km away. Members of groups often sing together. It is thought that vocalizations serve to advertise territories, maintain contact between group members, and convey information on age, sex, and reproductive condition of individuals. Avahis and sifakas also use vocalizations extensively in territorial advertisement and distance communication. In fact, the name "sifaka" comes from the explosive sound they make in response to threats, sounding like "see-fak." The sound is accompanied by a rapid jerk of the head and is often given several times in quick succession. Scent marking has been reported in sifakas. (Mittermeier, et al., 2006; Nowak, 1991)
All indriids are vegetarians, eating leaves, buds, fruit, bark, and flowers. They occupy a plant-eating primate niche that is occupied by howler monkeys in the neotropics and and leaf-eating monkeys in Africa and Asia. Their salivary glands are enlarged, as in African and Asian leaf-eating monkeys. (Mittermeier, et al., 2006; Nowak, 1991; Tattersal, 1982)
Indriids are important folivores in their native ecosystems, impacting plant communities. (Nowak, 1991)
Indriids are important members of their native ecosystems. The unique nature of indriids means they are the focus of ecotourism activities that benefit local people. Indriids are also kept in zoos and are the focus of research on evolution. (Nowak, 1991)
There are no known negative effects of indriids on humans.
All Malagasy primates are threatened, primarily by habitat destruction. Indriids are protected by law in Madagascar, but habitat destruction continues. Indris are also protected by local custom. (Mittermeier, et al., 2006; Nowak, 1991)
Indriids are known from Pleistocene fossils.
Tanya Dewey (author), Animal Diversity Web.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
uses sound to communicate
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
Referring to an animal that lives in trees; tree-climbing.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
an animal that mainly eats leaves.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
An animal that eats mainly plants or parts of plants.
animals that live only on an island or set of islands.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
Mittermeier, R., W. Konstant, F. Hawkins, E. Louis, O. Langrand, J. Ratsimbazafy, R. Rasoloarison, J. Ganzhorn, S. Rajaobelina, I. Tattersall, D. Meyers. 2006. Lemurs of Madagascar. Colombia: Conservational International.
Nowak, R. 1991. Walker's Mammals of the World, Volume 1. Baltimore: The Johns Hopkins University Press.
Tattersal, I. 1982. Primates of Madagascar. New York: Columbia University Press.
Wilson, D., D. Reeder. 2005. Mammal Species of the World. Baltimore: The Johns Hopkins University Press.
de Magalhães, J. 2008. "Propithecus coquereli" (On-line). AnAge: The Animal Ageing and Longevity Database. Accessed November 29, 2008 at http://genomics.senescence.info/species/.