The indri ( / ˈ ɪ n d r i / ; Indri indri ), also called the babakoto , is one of the largest living lemurs. It has a body length of about 64–72 cm (25–28 1⁄2 in) and weighs between 6 and 9.5 kg (13 and 21 lb). Its fur is black and white, and it stands upright when climbing or clinging. The indri mates with one partner and lives in small family groups. These groups move through the tops of trees and eat mainly leaves, but also seeds, fruits, and flowers. They are very vocal and use singing, roaring, and other sounds to communicate with other groups.

The indri is active during the day and lives in trees. It is related to sifakas and is found only in Madagascar. The people of Madagascar respect the indri, and it appears in many of their stories and myths. The main dangers to the indri include habitat loss and broken forests caused by farming, cutting trees for fuel, and logging. People also hunt the indri, even though some traditions discourage this. The International Union for Conservation of Nature has classified the indri as "critically endangered."

Etymology

The name "indri" probably comes from a Malagasy word for the animal, "endrina." A common but wrong story says the name comes from "indry," which means "there" or "there it is." A French scientist named Pierre Sonnerat, who first described the animal, may have heard a Malagasy person point out the animal and took the word they said as the animal's name. Some people think he may have heard the local name "endrina," which is also used for the animal. Another Malagasy name for the animal is "babakoto." "Babakoto" is often translated as "ancestor" or "father," though other meanings are possible. The word "koto" means "little boy" in Malagasy, and "Rakoto" is a common name with "koto" as its shortened form. Since "baba" means "father," "babakoto" might mean "father of a little boy" or "father of Rakoto." Stories about the animal often include a father-son relationship, which helps explain the meaning of the name "babakoto."

Physical characteristics

The indri is the second-largest lemur still living today, along with the diademed sifaka. Both species weigh about 6.5 kg on average. The indri can weigh up to 9.0 kg (19 3⁄4 lb) to 9.5 kg (21 lb), and possibly up to 15 kg (33 lb). Its body length is 64–72 cm (2 ft 1 in – 2 ft 4 1⁄2 in), and it can stretch to nearly 120 cm (4 ft) when its legs are fully extended.

The indri moves by clinging to trees and leaping between them, keeping its body upright while traveling or resting. It has long, strong legs used to jump from tree to tree. Its large greenish eyes and black face are surrounded by round, fuzzy ears. Unlike other living lemurs, the indri has only a short tail. Its silky fur is mostly black, with white patches on the limbs, neck, crown, and lower back. Different groups of indris show wide differences in color, with some northern groups being mostly or entirely black. The face has pale black skin, and sometimes white fur grows around it.

Because of these color differences, Colin Groves identified two subspecies of the indri in 2005: the dark Indri indri indri in the northern part of its range and the lighter Indri indri variegatus in the southern part. Later editions of Lemurs of Madagascar by Russell Mittermeier and others do not recognize this classification. Recent studies suggest that the indri’s color and physical differences change gradually across its range.

• In Andasibe-Mantadia National Park
• Juvenile
• Adult with juvenile

Behavior

The indri stays with one mate for life, finding a new partner only after the death of its current mate. It lives in small groups made up of a male and female pair and their young offspring. In forests that are broken into smaller pieces, the indri may live in larger groups with multiple generations. When forests are fragmented, it becomes harder for large groups to split into smaller ones.

Like many lemur species, the indri lives in a society where females are the leaders. The dominant female often pushes males to lower branches and areas with less food. She usually leads the group when they move.

Groups often travel 300–700 meters each day, with most movement happening in midsummer to find fruit. Indris sleep in trees about 10–30 meters above the ground, typically alone or in pairs. Young female indris, and sometimes adult females, may quietly wrestle for a few seconds to 15 minutes. Members of a group often urinate and defecate together at specific spots in their territory.

Indris reach sexual maturity between 7 and 9 years old. Female indris give birth every two to three years, with a pregnancy lasting about 120–150 days. Babies are usually born in May or June. The mother is the main caregiver, but the father stays with his mate and offspring. Newborns are mostly or completely black and begin to show white fur (if any) between four and six months of age. Babies cling to their mother’s belly until they are four or five months old, then move to her back. Indris start to act independently at eight months but remain dependent on their mothers until at least two years old.

The indri makes loud, unique songs that can last 45 seconds to over three minutes. These songs often follow a three-part pattern. A short roaring sequence usually begins the song, with all group members except the youngest participating. The main song is led by the adult pair, who produce long notes lasting up to five seconds. This is followed by a series of sounds that start high and gradually become lower. Sometimes, two or more indris coordinate their sounds to create a duet.

Different groups of indris often sing one after another, responding to each other. These songs help groups stay in contact, mark territory, share information about the environment, and signal reproductive status or dangers. Indris may sing after events like thunder, airplanes, bird calls, or other lemur calls. A group may sing up to seven times a day, with the most singing happening between 7 and 11 am. Singing is most frequent during the breeding season from December to March.

Other indri sounds include a "roar," used to warn of birds of prey like hawks, and a "hoot" or "honk," used to warn of ground predators like the fossa. Other sounds include "grunts," "kisses," "wheezes," and "hums," but their purposes are not fully understood. Before singing, indris move to the tops of trees, allowing their calls to be heard up to 4 kilometers away.

The indri eats plants, mainly young, tender leaves, but also eats seeds, fruits, and flowers. Female indris prefer immature leaves more than males and spend more time searching for them. Many types of plants are eaten, with those from the laurel family being especially common. The indri eats very little non-tree vegetation.

To eat, the indri uses its teeth to pluck leaves or other plant parts and its hands to bring branches closer to its mouth. Female indris who are ready to reproduce have better access to food and forage higher in trees than males.

Distribution

This lemur lives in lowland and mountain forests along the eastern coast of Madagascar, from the Réserve Spéciale d'Anjanaharibe-Sud in the north to the Mangoro River in the south. They are not found in the Masoala Peninsula or the Marojejy National Park, even though both areas are near forests where indri live within 40 kilometers.

Relationship with humans

In Madagascar, the indri is respected and protected by fady, which are traditional rules. Many stories explain the indri’s origins, but all describe it as a sacred animal that must not be hunted or harmed.

One story tells of a man who went hunting and never returned. His son searched for him and also disappeared. Villagers later found two large lemurs in the trees—the first indri. The boy and his father had changed into indris. In some versions, only the son changes, and the cries of the babakoto bird sound like the father’s cries for his lost son.

Like its sifaka relatives, the indri often sits in the sun with its legs crossed, back straight, hands low, and eyes half-closed. Scientists are not sure if this behavior means the indri is worshiping the sun, as the term may be human-like. However, many Malagasy people believe the indri honors the sun.

The first film of an indri was recorded using tape recordings during an expedition that inspired David Attenborough’s 1961 BBC series Zoo Quest to Madagascar.

The indri is critically endangered. Scientists estimate there are between 1,000 and 10,000 individuals, but the population is decreasing quickly and may drop by 80% in the next 36 years. The main threats are habitat loss and destruction from farming, collecting fuelwood, and logging, even in protected areas.

Despite fady that protect the indri, people still hunt it. Changes in culture and migration have weakened traditional beliefs. Some people who are not allowed to eat or kill indris find ways to break these rules. In some regions, indri meat is considered a special food.

Only one indri has lived more than a year in captivity, and none have had babies while in captivity.