Indri

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TAXONOMY

Suborder: Strepsirrhini
Infraorder: Lemuriformes
Superfamily: Lemuroidea
Family: Indriidae
Genus: Indri
Species: I. indri
Subspecies: I. i. indri, I. i. variegatus

Other names: I. indri: indri, indris; indri (Dutch); indri, indri à queue courte (French); indri colicorto (Spanish); indri (Swedish).

The genus Indri is monotypic with the one species divided into two subspecies (Groves 2005).

Conservation status: Endangered


Life span: Unknown
Total population: Unknown
Regions: Eastern Madagascar
Gestation: 119-154 days
Height: 62.6 cm (M & F)
Weight: 6.8 kg (M & F)


MORPHOLOGY

Indri
Indri indri

The largest of the Malagasy lemurs is the indri (some argue that this distinction is shared with Propithecus diadema diadema), a unique animal that is the sole lemur with a short, vestigial tail that appears stump-like (Pollock 1975a; Powzyk & Thalmann 2003; Mittermeier et al. 2006; 2008). Indris weigh on average 6.8 kg (15.0 lb), with an average head and body length of 62.6 cm (24.6 in) and a short tail averaging 5.3 cm (2.1 in) (Zaonarivelo et al. 2007). Females weigh more than males (Glander & Powzyk 1998). All indris have yellow eyes and large black ears (Thalmann et al. 1993; Mittermeier et al. 2008). The species also possesses a toothcomb which it uses for grooming and feeding comprised of four teeth, two incisors and two canines (Powzyk & Mowry 2006). Overall, they are black with some white pelage, although the exact mixture of black and white is variable by location and by individual within their north/south range. Individuals in the south have more white in their coloration (Thalmann et al. 1993; Mittermeier et al. 2006; 2008). Pelage is graded between northern and southern forms, with intermediate coloration seen between the northern and southern extremes. Northern indris (I. i. indri) are mostly black have a light ring around the black face and the rest of the head is black (Thalmann et al. 1993; Mittermeier et al. 2008). They have a white, forward facing triangle on the posterior of their torso (pygal patch) as well as a white tail and sides and light heels (Thalmann et al. 1993; Powzyk & Thalmann 2003). Southern indris (I. i. variegatus) lack a white face ring, but have a black face and the back of the head is white. In general, southern forms usually have more white coloration than their northern counterparts and their outer limbs are lighter, often white or grey (Thalmann et al. 1993).

Indris are among the most arboreal of the Malagasy lemurs (usually avoiding the ground), moving through their environment through ricochetal leaping or vertical climbing and leaping (Rand 1935; Mittermeier et al. 2006; Powzyk & Mowry 2006). Overall, their locomotion consists mostly of leaping between tree trunks, during which the body is held close to vertical with the arms outstretched (Petter & Peyriéras 1972; Powzyk & Mowry 2006). There are some reports of terrestrial bipedal locomotion (Mittermeier et al. 2006).

Indris are extremely hard to maintain in captivity and currently there are none in zoos worldwide (Thalmann et al. 1993; Britt et al. 2002; http://www.isis.org).

RANGE

CURRENT RANGE MAPS (IUCN REDLIST):
Indri indri

Like all lemurs, indris are found only on Madagascar, but are restricted to a north/south strip of the eastern rainforests of the island (Thalmann et al. 1993). The northernmost locality where they are found is the Anjanaharibe-Sud Special Reserve (Thalmann et al. 1993). The southernmost limit is south of the Bemarivo River but north of the Mangoro river (Petter et al. 1977). Indris are not present on the Masoala Peninsula, a large peninsula in the northeastern part of the island, nor are they found in the Marojejy National Park, just northeast of their northernmost locality (Petter et al. 1977; Tattersall 1977; Powzyk & Thalmann 2003; Mittermeier et al. 2006).

HABITAT

Indris are found in the primary and secondary eastern tropical rainforest or humid forests of Madagscar, in both lowland mid-altitude and montane forests and including some disturbed habitats (Petter & Peyriéras 1974; Thalmann et al. 1993; Britt et al. 2002; Powzyk & Thalmann 2003; Glessner & Britt 2005; Mittermeier et al. 2006; Powzyk & Mowry 2006). They are often found in mountainous habitats or habitats on steep terrain with numerous ridges and valleys (Petter & Peyriéras 1974; Pollock 1975a; Thalmann et al. 1993; Britt et al. 2002). Indris are found to range from nearly sea level to an altitude of 1800 meters (5905.5 feet) (Rand 1935; reviewed in Goodman & Ganzhorn 2004).

At the Betampona Reserve in eastern Madagascar, temperatures average 21°C (69.8°F) (averages are cooler between June and September, averaging 18°C (64.4°F)) with an annual rainfall of 412.9 cm (162.6 in). The most rain falls between January-March and June-August with no true dry months, although October and November are drier than the rest of the year (Britt et al. 2002).

ECOLOGY

Indris are predominately folivorous, consuming predominantly leaves (mostly young) but also fruits, seeds, and flowers (Pollock 1975a; 1977; Britt et al. 2002; Powzyk & Mowry 2003; 2006). They are both dentally and digestively adapted for their diet (reviewed in Powzyk & Mowry 2006). At the Mantadia National Park in eastern Madagascar, indris ate 76 species of plants and spent their feeding time consuming young leaves (72.3%), fruits (16.4%), and flowers (6.7%). Bark was also consumed at this study site, as well as galls, other plant parts, leaf petioles and new branch tips (Powzyk 1997 cited in Powzyk & Mowry 2003; Powzyk & Mowry 2003). Mature leaves are only rarely consumed; only around 1.4% of feeding time is spent on them (Powzyk 1997 cited in Powzyk & Mowry 2006). Some studies report that soil is only rarely consumed, while others indicate that geophagy is common (Britt et al. 2002; Powzyk & Thalmann 2003). In fact, at Mantadia National Park, Indris consumed soil weekly (Joyce Powzyk pers comm.) At Betampona Reserve also in eastern Madagascar, 42 species of plants were eaten, including immature foliage (73.4% of records), mature foliage (7.2%), fruit (5.5%), flowers (5.3%), bark. (4.5%), seeds (2.7%), and petioles (1.3%). Immature leaves are the most important part of the diet year-round at Betampona, while seasonal peaks in consumption of other food items are seen. Peaks in consumption of mature leaves occur in April and May, and September and November, while there are also peaks in the eating of fruit (April and July-September), seeds (February-March), flowers (April-June, October) and petioles (September) (Britt et al. 2002).

Indri
Indri indri

Indris feed by breaking off the desired part of the plant with their mouth, not with their hands (Powzyk & Thalmann 2003). Most feeding occurs while sitting or standing above a branch (78%) but may also occur while clinging vertically to a substrate (21.6%) (Britt et al. 2002).

Indris are strictly diurnal with the daily activity period usually lasting between only 5-11 hours, with longer activity periods seen in the summer (Pollock 1975a; 1977; Powzyk & Mowry 2006). At Betampona for example, indris did not start feeding before 9am and were finished with all activity by 3pm (Britt et al. 2002). Feeding usually comprises around 40% of the daily activities, and the species rests a large proportion of their time as well, often around 8 of the daylight hours (Pollock 1977; Powzyk 1997 cited in Britt et al. 2002; Britt et al. 2002; Powzyk & Thalmann 2003). Social activities comprise only a very small portion of the daily activities; in one study only 2% (Pollock 1975a; 1979a).

In the morning, group members usually start activity at around the same time followed by short feeding bout and a short group movement and synchronous group defecation and urination. All-day constant feeding then ensues until near the end of the activity period, when there is a grooming session and activity is finished for the day (Pollock 1975a). Indris sleep in trees between 30 and 100 feet (9.1 and 30.5 meters) off of the forest floor (Pollock 1975a).

Home range and daily path vary by location and differences are mostly due to habitat quality (Powzyk & Thalmann 2003). For example, indri home ranges are much larger in Mantadia National Park than in disturbed forests (Joyce Powzyk pers comm.). Recorded average home ranges are 0.27 km² (0.1 mi²) but other recorded group ranges included 0.15., 0.18, 0.18, and 0.3 km² (0.06, 0.07, 0.07 and 0.12 mi²) and as high as 0.4 km² (0.15 mi²) (Pollock 1979a; 1979b; Glessner & Britt 2005; Mittermeier et al. 2006; Joyce Powzyk pers comm.). The indri daily path is usually around 774 m (2539.4 feet), but can range between 300 and 700 m (984.3 and 2296.6 feet) (Pollock 1975a; Pollock 1979b; Powzyk 1997 cited in Powzyk & Thalmann 2003; Powzyk & Mowry 2006). The extent of the territory is generally visited every 8-14 days (Powzyk 1997 cited in Powzyk & Thalmann 2003). In the austral winter, indris will sometimes descend to lower levels of trees to avoid biting insects (Thalmann et al. 1993).

Indris can be sympatric with a number of other lemur species. For example, at Betampona Natural Reserve, they are sympatric with mouse lemurs (Microcebus sp.), greater dwarf lemurs (Cheirogaleus major), eastern fork-marked dwarf lemurs (Phaner furcifer), sportive lemurs (Lepilemur mustelinus), aye-ayes (Daubentonia madagascariensis), grey gentle lemurs (Hapalemur griseus), white-fronted lemurs (Eulemur albifrons), black-and-white ruffed lemurs (Varecia variegata), eastern avahis (Avahi laniger), and diademed sifakas (Propithecus diadema) (Glessner & Britt 2005).

Indris may be susceptible to predation from diurnal raptors and infants have been observed being attacked by such predators (Goodman et al. 1993; Joyce Powzyk pers comm.).

Content last modified: July 1, 2010

Written by Kurt Gron. Reviewed by Joyce Powzyk.

Cite this page as:
Gron KJ. 2010 July 1. Primate Factsheets: Indri (Indri indri) Taxonomy, Morphology, & Ecology . <http://pin.primate.wisc.edu/factsheets/entry/indri/taxon>. Accessed 2020 July 22.

SOCIAL ORGANIZATION AND BEHAVIOR

Indri group sizes are small, averaging only 3.1 individuals (usually between two and six individuals) and typically containing a reproducing pair and their offspring (Petter & Peyriéras 1974; Pollock 1975a; Powzyk & Thalmann 2003). Group members usually remain within 100m of another member of the group (Pollock 1975a).

Indri
Indri indri

Several short studies of calling in indris have shown that calling bouts in the species may play a role in their territorial defense and announcement, as each group defends an exclusive territory (Oliver & O’Connor 1980; Pollock 1979a; Geissmann & Mutschler 2006; Mittermeier et al. 2006; Powzyk & Mowry 2006). Although evidence is still somewhat ambiguous, the limits of each group’s territory seem to be for the most part maintained and respected through some means which may also include scent-marking (Pollock 1975a; 1979b). It is possible that physical confrontations also play a role (Pollock 1975a). Most calling is in the morning (with the most in the summer), usually ending by around noon (Thalmann et al. 1993; Powzyk 1997 cited in Powzyk & Thalmann 2003; Geissmann & Mutschler 2006; Mittermeier et al. 2006).

Adult females are dominant to adult males (Pollock 1979a). The majority of aggression is related to feeding and in such aggression females usually come out on top (Pollock 1979a; 1979b). In fact, females seem to dictate exactly how much feeding males actually perform (Pollock 1979b). Affiliative interactions between indris include allogrooming (of inaccessible body areas by others), and play-wrestling (mostly young individuals) (Pollock 1979a).

Males might migrate to form new groups (Pollock 1986).

REPRODUCTION

Data on reproduction in indris are extremely limited, likely in part due to the difficulties with captive management. Indris are monogamous, and adults will find new mates only upon death of a previous one (Powzyk & Thalmann 2003). Anecdotal observations describe a suspensory ventro-ventral copulation posture (Thalmann et al. 1993). Males initiate copulation by licking and smelling of the female genitalia (Pollock 1975a). Mating and births are seasonal, with births falling in May and June and Mating in December through March (Garbutt 1999; Mittermeier et al. 2006).

Sexual maturity is reached between 7 and 9 years old (Garbutt 1999). Gestation is estimated at 119-154 days (Pollock 1975a). In the wild, the interbirth interval is around two or three years (Powzyk & Thalmann 2003).

PARENTAL CARE

Akin to the reproductive data, information about the development of infants and parental care is extremely limited. For the first 2 or 3 months of life, infants are all black (except for the white patch on the torso), and then change to a more adult-like pelage (Powzyk & Thalmann 2003; Powzyk & Mowry 2006). The primary caregiver is the mother (Powzyk & Thalmann 2003). Births usually occur in May or June (but can as late as August) (Garbutt 1999; Mittermeier et al. 2006). One wild infant suckled in bouts three or four times a day. Carrying is on the mother’s ventrum before 4 or 5 months old, after which the infant rides on the mother’s back. The first transfer off the mother is between 4-6 weeks of age, and gnawing of solid food commences around two months old. At an age of 8 months old, the infant moves by itself. Weaning is before one year of age (Pollock 1975a).

COMMUNICATION

In general, indris use calling more than scent-marking in communication, and vocalizations may be audible for over 2 kilometers (1.2 miles) (Oliver & O’Connor 1980; Powzyk & Mowry 2006). Calls are made louder by a laryngeal sac possessed by the species and are generally emitted as highly variable long, loud songs, and by adults of both sexes (Petter & Peyriéras 1972; Thalmann et al. 1993; reviewed in Geissmann & Mutschler 2006). Loud calls are divided into three general classes of vocalization: “waa notes,” “the song proper,” and the “descending phrase sequence” (Thalmann et al. 1993). Indri songs can last anywhere between 40 seconds to around 4 minutes, followed by a resumption of normal activities (Pollock 1986). Calling in indris can be spontaneous, in response to the calls of other groups (contagious calling, in which songs can be heard sequentially through the forest as each neighboring group participates), or more rarely in response to disturbance (Oliver & O’Connor 1980; Pollock 1986; Powzyk & Thalmann 2003; Powzyk & Mowry 2006). Calling usually occurs at least once per diurnal cycle, but the total number of calls heard varies by the day (Pollock 1986). There is seasonal variation in the emission of indri songs, with the most songs heard in the middle of the astral summer (December and January) (Pollock 1986).

Functions of indri songs are generally unclear, but may include communicating information about reproduction, mated status, group size, age and sex, about territorial extent, in disputes about territory, or about territorial location and presence in the forest (Oliver & O’Connor 1980; Pollock 1986; Powzyk 1997 cited in Gould & Sauther 2007; Powzyk & Mowry 2006). Calling also may function in individual recognition, and to bring group members together (Pollock 1986; Powzyk & Mowry 2006). Predator alarm calls are “roars” which are also often heard directly preceding the longer songs (Pollock 1986). Honks also probably show alarm (Thalmann et al. 1993). Calling at night is not unheard of, even though the animals are inactive during that time (Pollock 1986; Thalmann et al. 1993). Less calling is heard during inclement weather (Pollock 1986). Other types of call include “grunts,” “kisses,” and “wheezes,” as well as “hums” that are heard before group movement (Pollock 1975b cited in Powzyk & Thalmann 2003).

Anogenital scent-marking has been observed in indris (Powzyk 1997 cited in Powzyk & Mowry 2006).

Content last modified: July 1, 2010

Written by Kurt Gron. Reviewed by Joyce Powzyk.

Cite this page as:
Gron KJ. 2010 July 1. Primate Factsheets: Indri (Indri indri) Behavior . <http://pin.primate.wisc.edu/factsheets/entry/indri/behav>. Accessed 2020 July 22.

 

INTERNATIONAL STATUS

CITES: Appendix II (What is CITES?)
IUCN Red List: I. indri: EN (What is Red List?)
Key: EN = Endangered
(Click on species name to see IUCN Red List entry, including detailed status assessment information.)

Indri
Indri indri

Indris have not been successfully kept in captivity, preventing captive breeding programs (Britt et al. 2002).

CONSERVATION THREATS

Threat: Human-Induced Habitat Loss and Degradation

As with many primates, the main threat to the survival of the indris is their loss of habitat, a process that is ongoing (Pollock 1984 cited in Mittermeier et al. 2006; Britt et al. 2002). This can be due to many causes, including slash-and-burn agriculture, selective logging, fuel wood acquisition, and logging (Pollock 1984 cited in Mittermeier et al. 2006; Powzyk & Thalmann 2003). Even if not clear-cut, fragmentation of habitats can isolate populations, as can roads and agriculture, profoundly altering their ecology and reproductive potential (Britt et al. 2002; Powzyk & Thalmann 2003).

Threat: Harvesting (hunting/gathering)

In some areas of the indri range, taboos exist against the hunting of the species (some stemming from its stump of a tail), although these are not applicable at all locations. Even in areas where taboos are present, immigration and selective adherence may permit some hunting to be taking place (Powzyk & Thalmann 2003; Mittermeier et al. 2006). Indris are therefore hunted for both meat and for their skins, often at high levels (Golden 2005 cited in Mittermeier et al. 2006).

LINKS TO MORE ABOUT CONSERVATION

CONSERVATION INFORMATION

CONSERVATION NEWS

ORGANIZATIONS INVOLVED IN Indri indri CONSERVATION

Content last modified: July 1, 2010

Written by Kurt Gron. Reviewed by Joyce Powzyk.

Cite this page as:
Gron KJ. 2010 July 1. Primate Factsheets: Indri (Indri indri) Conservation . <http://pin.primate.wisc.edu/factsheets/entry/indri/cons>. Accessed 2020 July 22.

The following references were used in the writing of this factsheet. To find current references for Indri, search PrimateLit.

REFERENCES

Britt A, Randriamandratonirina NJ, Glasscock KD, Iambana BR. 2002. Diet and feeding behaviour of Indri indri in a low-altitude rain forest. Folia Primatol 73(5):225-39.

Garbutt N. 1999. Mammals of Madagascar. Sussex (UK):Pica Pr. 320p.

Geissmann T, Mutschler T. 2006. Diurnal distribution of loud calls in sympatric wild indris (Indri indri) and ruffed lemurs (Varecia variegata): implications for call functions. Primates 47(4):393-6.

Indri artwork
Indri indri

Glander KE, Powzyk JA. 1998. Morphometrics of wild Indri indri and Propithecus diadema diadema. Folia Primatol 69(suppl 1):399

Glessner KDG, Britt A. 2005. Population density and home range size of Indri indri in a protected low altitude rain forest. Int J Primatol 26(4):855-72.

Golden C. 2005. Eaten to endangerment: mammal hunting and the bushmeat trade in Madagascar’s Makira Forest. Undergraduate thesis, Harvard University.

Goodman SM, Ganzhorn JU. 2004. Biogeography of lemurs in the humid forests of Madagascar: the role of elevational distribution and rivers. J Biogeogr 31(1):47-55.

Goodman SM, O’Connor S, Langrand O. 1993. A review of predation on lemurs: implications for the evolution of social behavior in small, nocturnal primates. In: Kappeler PM, Ganzhorn JU, editors. Lemur social systems and their ecological basis. New York: Plenum Pr. p51-66.

Gould L, Sauther M. 2007. Lemuriformes. In: Campbell CJ, Fuentes A, MacKinnon KC, Panger M, Bearder SK, editors. Primates in perspective. New York:Oxford U Pr. p46-72.

Groves C. 2005. Order primates. In: Wilson DE, Reeder DM, editors. Mammal species of the world: a taxonomic and geographic reference, third edition, volume 1. Baltimore (MD): Johns Hopkins U Pr. p111-84.

Mittermeier RA, Ganzhorn JU, Konstant WR, Glander K, Tattersall I, Groves CP, Rylands AB, Hapke A, Ratsimbazafy J, Mayor MI, Louis Jr EE, Rumpler Y, Schwitzer C, Rasoloarison RM. 2008. Lemur diversity in Madagascar. Int J Primatol 29(6):1607-56.

Mittermeier RA, Konstant WR, Hawkins F, Louis EE, Langrand O, Ratsimbazafy J, Rasoloarison R, Ganzhorn JU, Rajaobelina S, Tattersall I, Meyers DM. 2006. Lemurs of Madagascar. Washington, D.C.: Conservation International. 520p.

Oliver WLR, O’Connor SM. 1980. Circadian distribution of Indri indri group vocalizations: a short period sampling at two study sites near Perinet, eastern Madagascar. Dodo 17:19-27.

Petter J-J, Albignac R, Rupler Y. 1977. Mammifères Lémuriens (Primates Prosimiens). Faune de Madagascar: 44. Paris:ORSTOM/CNRS. 513p.

Petter J-J, Peyriéras A. 1974. A study of population and density and home ranges of Indri indri in Madagascar. In: Martin RD, Doyle GA, Walker AC, editors. Prosimian biology. Pittsburgh (PA): U Pittsburgh Pr. p39-48.

Pollock JI. 1977. The ecology and sociology of feeding in Indri indri. In: Clutton-Brock TH, editor. Primate ecology: studies of feeding and ranging behaviour in lemurs, monkeys and apes. London: Academic Pr. p37-69.

Pollock JI. 1979a. Female dominance in Indri indri. Folia Primatol 31:143-64.

Pollock JI. 1975a. Field observations on Indri indri: a preliminary report. In: Tattersall I, Sussman RW, editors. Lemur Biology. New York:Plenum Pr. p287-311.

Pollock JI. 1984. Preliminary report on a mission to Madagascar by Dr. J. I. Pollock in August and September 1984. Unpublished report to WWF-US Primate Program.

Pollock JI. 1975b. The social behaviour and ecology of Indri indri. PhD dissertation, University of London.

Pollock JI. 1986. The song of the indris (Indri indri; Primates: Lemuroidea): natural history, form, and function. Intl J Primatol 7(3):225-64.

Pollock JI. 1979b. Spatial distribution and ranging behavior in lemurs. In: Doyle GA, Martin RD, editors. The study of prosimian behavior. New York: Academic Pr. p359-409.

Powzyk JA, Mowry CB. 2003. Dietary and feeding differences between sympatric Propithecus diadema diadema and Indri indri. Int J Primatol 24(6):1143-62.

Powzyk J, Thalmann U. 2003. Indri indri, Indri. In: Goodman SM, Benstead JP, editors. The natural history of Madagascar. Chicago: University of Chicago Press. p1342-45.

Powzyk JA, Mowry CB. 2006. The feeding ecology and related adaptations of Indri indri. In: Gould L, Sauther ML, editors. Lemurs: ecology and adaptation. New York:Springer. p353-68.

Powzyk JA. 1997. The socio-ecology of two sympatric indriids: Propithecus diadema diadema and Indri indri, a comparison of feeding strategies and their possible repercussions on species-specific behaviors. PhD dissertation, Duke University.

Rand AL. 1935. On the habits of some Madagascar mammals. J Mammal 16(2):89-104.

Tattersall I. 1977. Distribution of the Malagasy lemurs, part 1: the lemurs of northern Madagascar. Ann New York Acad Sci 293:160-9.

Thalmann U, Geissmann T, Simona A, Mutschler T. 1993. The indris of Anjanaharibe-Sud, northeastern Madagascar. Int J Primatol 14(3):357-81.

Zaonarivelo JR, Andriantompohavana R, Engberg SE, Kelley SG, Randriamanana J-C, Louis Jr EE, Brenneman RA. 2007. Morphometric data for Indri (Indri indri) collected from ten forest fragments in eastern Madagascar. Lemur News 12:17-21.

Content last modified: July 1, 2010

IMAGES

Indri indri
Photo: Christina Grassi
Indri indri
Photo: Claire Santorelli
Indri indri
Photo: Kevin Schafer
Indri indri
Photo: Primates in Art & Illustration Collection
Indri indri
Photo: Sarah Hrdy

 

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