Indri
Indri indri

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).

MORPHOLOGY

Photo: Christina Grassi

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

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).

Photo: Claire Santorelli

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>. Accessed 2012 February 9.