Their songs belong to the most impressive that animal kingdom has: You can hear the Indris’ (Indri indri) voices in the forest kilometers away, and the sound a little sad. The parent couple of a family always starts the songs, thus marking its territory, communicating with other families and warning their own family members of potential hazards such as birds of prey or Fossas. The other animals of the family join the song to make it sound louder and more powerful. Indris sing most in the morning – it is an unbelievable, amazing experience to begin your day with such a chorus in the rainforest. And they only occur in Madagascar!
Indris are the largest lemurs of Madagascar, and look like teddy bears: White fur frames the black face, and the black, circular ears are covered in thick plush. They can reach weights up to 10 kg with a body size of about 70 cm. With stretched arms and legs, they have a length of impressive 120 cm. But most Indris remain smaller and slender like most other lemurs, and much under the maximum weight.
Seemingly feather-light, they jump from tree to tree. Very rarely Indris touch the ground, their whole lifecycle is adapted to the tree tops in airy heights until 1800 m above sea level. Their only home are the rainforests along the eastoast between Andapa in the north and Anosibe An’Ala at the edge of the central highlands. Among the national parks and reserves they inhabit are Mananara-Nord, Andasibe-Mantadia, Anjanaharibe-South, Zahamena and Makira, Betampona, Mangerivola, Ambatovaky as well as Marotandrano.
In Madagascar, the Indri is also called Babakoto and has its own, very important place in myths and legends. People say that Indris are closely related to human beings, maybe even were some in former times. This belief may have something to do with the fact that Indris – in contrast to all other lemurs of Madagascar – lack a long, elegant tail. They only have a stumpy tail, and you barely recognize it inside the thick fur. Like humans, Indris are monogamous and have only one partner for their whole lifetime. Only if the first partner died, an Indri will look for a new companion.
Indris are the gentle giants among lemurs: They hardly have heated disputes among each others, and confrontations with other families are mostly carried out in a peaceful manner. Anyhow, different families do not meet each the others on a daily base, since they are scattered over a wide area and only a relatively low average of 7 to maximally 23 Indris lives in one square kilometer. Together with their offspring, an older couple inhabits a territory of less than a half square kilometer. During daytime, they roam this area searching the trees for food – and more seldom – defend it against intruders. Only one couple and its offspring makes a group, there are regularly no groups with mixed families.
The diet of Indris is extraordinary, and mainly consists of young leaves from more than 40 different tree species. Their favorite food are plants of the laurel family. From time to time, they augment the leaf diet with flowers, fruits, seeds and bark – depending on what is available in the forest. During forage, they move an average of 350 to 700 meters per day. Around noon, Indri families take a rest in high trees and then continue foraging in the afternoon. They sleep in branches 10 to 30 meters above the ground. But they do not build nests like apes, Indris simply cuddle up together in pairs or lean alone on a branch fork.
A female Indri is receptive only few days a year, probably even only in one single day at a certain time. The male must bide exactly her time to reproduce successfully. Mostly, mating happens in the rainy season, when food supply is rich and prosperous. Each female bears one single young only every two or three years, always around May or June after four to five months of pregnancy.
New born Indris are jet-black, just a hand full of lemur, and hold on their mothers’ belly. At an age of three, four months, the small lemurs dare to climb on their mothers’ back and begin to discover the world with their big, bright blue eyes. Now it is September or October, the best time to watch Indri families. Now some young Indris are already able to discover trees on their own and do not remain completely hidden like before. In most populations, now the white fur starts to appear. The fur coloration varies in each region. In Anjozorobe and Manakara, they also have completely black Indris. Solely entirely white Indris have not been seen yet.
Especially females train their abilities in playful wrestles. They are to lead a family later on, and thus have to learn mimics, gestures, songs and hierarchy behavior perfectly. At an age of eight months, the young Indris are almost independent of their mothers, but continue to share feeding and sleeping places until the age of two years. This is the time when eye color of the young ones changes from baby blue to greenish yellow.
Appropriate to their teddy bear like look, Indris stay children for a long time. They do not become sexually mature before an age of seven to nine years. Then it is time to leave their family and found an own. Surprisingly, bachelors among Indris sing other songs than their family: They try on purpose to sing lower or higher pitches and asynchronously to emphasize their own attractiveness. Simply said: Who sings more beautiful and thus attracts more attention, has less problems to find a partner. Besides their characteristic songs, Indris have a wide array of different noises like all other lemurs.
The IUCN red list of threatened species lists the Indri as critically endangered. Their habitat are intact rainforests, but those disappear more and more from the red island. Slash-and-burn agriculture frightens the animals away into isolated forest patches, where they finally fall victims to the flames. People in need of firewood chop down complete forests. Few Malagasy even hunt and eat Indris although there are centuries old myths around these animals and traditional fadys (taboos) of many tribes prohibit to harm them. Research activities around Makira plateau carried out that Indri meat commands top prices on markets and is estimated to be especially precious among people – although illegal. Additionally, fadys are bypassed or minimized by immigration of other tribes, that have no fadys concerning the Indri yet.
Today, an existing population of 1000 to 10.000 Indris is estimated to live in Madagascar, but the population is declining. There is few research about the count of individuals, and it lacks money to protect the residual rainforests. If the Indri populations keep declining, scientists say that more than 80 % of the up to date population will be gone in less than 40 years from now. A threatening forecast – our task now is to stop this development. Governmental regulation of protected areas, controls to enhance protection and especially possibilities for the people to earn their life from ecotourism and sustainable agriculture instead of cutting forests are part of the strategy.
The best places to meet the Indris in their natural habitat, are national park Andasibe-Mantadia and the reserves Mitsinjo, Anjozorobe, Betampona and Akanin’ny Nofy. If you meet them once, you will succumb to Madagascar’s magic. By the way, Indris cannot be seen in zoos. Their diet is so special and unique, that no animal park of the world has succeeded yet to feed and keep Indris for more than one year. One more reason to come to Madagascar and keep their natural habitat alive.
- The Indris have got rhythm! Timing and pitch variation of a primate song examined between sexes and age classes
Frontiers in NeuroScience 2016 | Authors: Marco Gamba, Valeria Torti et al
- Effects of anthropogenic disturbance on Indri health in Madagascar
American Journal of Primatology 2011 | Authors: Randall Junge, Meredith Barrett, Anne Yoder
- Not just a pretty song: an overview of the vocal repertoire of Indri indri
Journal of Anthropological Sciences 2011 | Authors: Maretti, Sorrentino et al
- Population density and home range size if Indri indri in a protected low altitude rain forest
International Journal of Primatology 2005 | Authors: Kellie Glessner, Adam Britt