Influence of ranging and hierarchy on the habitat use pattern by asian elephant (elephas maximus) in the tropical forests of Southern India

Abstract

In tropical forests, resource quality and quantity change across habitats due to spatiotemporal varition in environmental conditions. Wide ranging species like elephants that adapted to live in different habitats have been documented to use different habitats in various seasons. Such movement generally has been attributed to environmental factors and its resultant variance in resource quality and quantity, assuming that all habitats are free to all the elephants to use optimally in any season. However, Asian elephant clans in Southern India have been documented to show hierarchy and spacing; besides environmental factors, there appears a behavioural factor in the use of habitat types among individual clans. This chapter presents the first quantitative information on elephants as to how ranging and spacing influence on use of habitat types and their preference by individual clan and bull, by monitoring the movement patterns of three clans and two bulls, ranging in a large contiguous habitats with high-density population of Asian elephants in Nilgiri Biosphere Reserve, Southern India, between 1991 and 1994. The results on habitat use pattern show that the number of habitat types used by clans and bulls varied among clans, bulls and between them. Such variations are attributed to spatial location of home range and home range fidelity. Therefore, though many habitat types were available in adjoining areas of their home, not all of them were used by all the clans and bulls. While some clans and bulls have used all types of habitat available in a population range, others have just restricted to one or two habitats round the year. Further, among overlapping clans, the intensity of use of various habitats and their habitat preferences were significantly different, and these have been related to the observed hierarchy in space use and its resultant spacing among overlapping clans. Therefore, it is revealed that apart from influence of environmental factors, hierarchy, a behavioural (social) factor, also plays an important role in the strategy of habitat use. The interclan encounter discussed in the Chap. 15 also goes in support of this view. Thus, the elephant clans are not free to use all the habitats of their choice and appeared to exhibit a hierarchy-based habitat use, which seems to fit with the Fretwell's 'ideal-despotic distribution' model of habitat selection rather than 'ideal-free distribution' as assumed by earlier studies. Such a hierarchy-based habitat use pattern among the elephant clans could result in dominant clans having prior access to good-quality habitat and food, thereby showing better survival and reproductive success.