Indriidaeindris, sifakas, and relatives

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Diversity

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)

Geographic Range

Indriids are endemic to Madagascar. (Mittermeier, et al., 2006; Nowak, 1991; Tattersal, 1982; Wilson and Reeder, 2005)

Habitat

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)

Physical Description

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)

  • Sexual Dimorphism
  • sexes alike

Reproduction

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)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-independence
    • protecting
      • male
      • female
  • post-independence association with parents

Lifespan/Longevity

A captive Propithecus coquereli lived for 30.5 years. Other Propithecus species have lived for more than 20 years in captivity. (de Magalhães, 2008; Nowak, 1991)

Behavior

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)

Communication and Perception

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)

Food Habits

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)

Predation

The only native predator of lemuroids in Madagascar are fossas (Cryptoprocta ferox). Humans also hunt indriids. (Mittermeier, et al., 2006; Nowak, 1991)

Ecosystem Roles

Indriids are important folivores in their native ecosystems, impacting plant communities. (Nowak, 1991)

Economic Importance for Humans: Positive

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)

  • Positive Impacts
  • ecotourism
  • research and education

Economic Importance for Humans: Negative

There are no known negative effects of indriids on humans.

Conservation Status

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)

  • IUCN Red List [Link]
    Not Evaluated

Other Comments

Indriids are known from Pleistocene fossils.

Contributors

Tanya Dewey (author), Animal Diversity Web.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

altricial

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.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

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.

chemical

uses smells or other chemicals to communicate

choruses

to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species

diurnal
  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

ecotourism

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.

endothermic

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.

folivore

an animal that mainly eats leaves.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

herbivore

An animal that eats mainly plants or parts of plants.

island endemic

animals that live only on an island or set of islands.

iteroparous

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).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

rainforest

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.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

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

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

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/.