The social behaviour and ecology of Indri Indri

A period of 15 months was spent studying the behaviour and ecology of Indri indri in the eastern rain-forest of Madagascar. Two groups were habituated to the observer and followed every six weeks for a complete year. Quantitatives sampling techniques were developed which allowed several animals' behaviour to be simultaneously recorded. Surveys were conducted in three areas of different botanical and topographical structure and censuses performed both at the beginning and end of the study. Some behavioural properties of a population of Indri were investigated in one study site by collecting data on vocal interactions between approximately 40 groups. The maintenance activities of the species are described and assessed. Seasonal and individual variation in behaviour are compared both in the groups studied and with other species. Social behaviour is analysed (1) by measures of animal interaction and (2) in terms of the inter-dependence of some individuals' behaviour with others. Measures of spacing and feeding are shown to be suitable to this approach. Evidence for the territoriality of the species is presented and its adaptive qualities considered. The roles of territory definition, declaration and occupation are contrasted and compared. The development of behaviour in infant and juvenile Indri is examined in terms of individual and social adaptations. Some facets of ecological and social differentiation with Indri society are proposed