- Suborder: Strepsirrhini
- Infraorder: Lemuriformes
- Superfamily: Lemuroidea
- Family: Indriidae
Indris are arguably the largest Malagasy lemurs. They are unique for their stump like vestigal tail (Pollock, 1975al Powzyk & Thalmann 2003). Indris weigh on average 15 pounds with a head and body length of 24.6 inches (Zaonarivelo et al. 2007). Females weight more than males (Glander & Powzyk, 1998). Indris have yellow eyes and black ears (Thalmann et al. 1993; Mittermeier et al. 2008). They are black with same white pelage. The proportions of black and white vary by north and south range and location. Southern populations tend to have more white relative to those in northern populations (Thalmann et al. 1993; Mittermeier et al. 2006; 2008). Like other strepsirrhines they have toothcomb (two incisors and canines fused together) that is used for grooming and feeding (Powzyk & Mowry 2006).
Indris are the most arboreal of the Malagasy lemurs. In order to move through their arboreal environment they use leaping and vertical climbing and leaping (Rand 1935; Mittermeier et al. 2006; Powzyk & Mowry 2006). Vertical climbing and leaping (VCL) consists of leaping between tree trucks while holding its body vertical (Petter & Peyriéras, 1972; Powzyk & Mowry 2006). However, they have also been reported as using terrestrial bipedalism (Mittermeier et al. 2006)
Indris are found in primary and secondary tropical rainforests, humid forests and montane forests (Petter & Peyriéras, 1974; Thalmann et al. 1993; Britt et al. 2002).
Indris are folivorous but will also eat fruits, seeds and flowers (Pollock 1975a; 1977; Powzyk & Mowry 2003; 2006). Indris feed via breaking off the plant with their mouth and not with their hands (Powzyk & Thalmann, 2003). Feeding usually makes up of 40% of their daily activities (Pollock 1977).
Indris are diurnal (Pollock, 1975a; 1977; Powzyk & Mowry, 2006).
Indris live in groups of approximately three individuals. Generally groups consist of a reproducing pair and their offspring (Peyriéras, 1974; Powzyk & Thalmann 2003). Adult females are dominant over adult males. Generally aggression occurs in feeding contexts (Pollock 1979a). Pollock (1979b) suggested females may actually dictate the amount of feedings males are allowed. Male will also known to migrate for form a new group (Pollock, 1986).
Indri indri is also known for their singing battles. During their singing, they will howl loudly in order to defend their territory. Rather than having any physical fights they simply have singing battles (Pollock, 1975; Pollock, 1986; Wranghum, 1987). Indri indri is difficult to explain in-group size due to the presence of extra pair copulation. Indri was first thought to be monogamous pairs with juvenile young in their group and several adults but appear to practice extra pair copulation (Redmond, 2008). Other research suggests that groups may be less stable and their composition of the groups may be much more variable then once thought (Wranghum, 1987). Singing involves chorusing of male, female and juveniles (Deputte, 1982). This singing will last forty to twenty fifty seconds and involve three to four roars uttered during the chorusing by group members (Pollock, 1986).
Indri indri is considered to be monogamous but appear to participate in extra pair copulation. Generally an Indri indri group is composed of a male and female and their offspring in a territory, these territories are maintained by loud singing. Not only does singing maintain territory but it also functions as a cohesive group call (Pollock, 1975; Pollock, 1986). The extra pair copulation involved the female going into a neighboring group and joining another male while not responding to her males call from her territory (Bonadonna et al. 2014). Extra pair copulation functions to help both the females due to her selecting a fitter male from another territory with possibly better genes and the male receiving this will also help him sire more offspring (Fisher, 1930). This will allow for more possible mating partners within the breeding season and lead to an increase for males to have more offspring and females to gain better mate choices (Matsumoto-Oda et al. 2007). Although Indri indri are thought to be monogamous they appear to participate in extra pair copulation for various reasons that in fact help both sexes (Bonadonna et al. 2014).
Females are the primary caregivers of infants. Infants are all black and will transition to a more adult pelage after approximately two to three months. Infants are generally born in May or June. The infant will suckle for four or five months. During their four to five months of suckling they will be carried on their mother’s ventrum before transitions to riding on its mothers back. By eight months of age they infant will move by itself. Weaning will occur at one year of age (Pollock, 1975a).
Sexual maturity is reached by seven to nine years of age (Garbutt, 1999). Gestation is approximately 119 to 154 days (Pollock, 1975a). The interbirth ratio is two to three years (Powzyk &Thalmann, 2003).
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.
Glander KE, Powzyk JA. 1998. Morphometric 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. Prosimians 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 fragm