Calf development, calf conspecific interactions, and the effect of calves on female social structure in the kabini Asian elephant population, southern India

Abstract

Group-living is widespread among vertebrates and is expected to provide benefits such as decreased predation, enhanced feeding success, and higher survival of young ones (for example, Holekamp et al. 1997, Clutton-Brock et al. 1999, Packer et al. 1990). In large mammals, in which adults have few natural predators and grouping is likely to increase feeding competition, higher survival of young ones may be an important benefit of group living. Better survival of young ones through decreased predation or infanticide may result from increased group size, active guarding of young, or increased vigilance (Lee 1987, Packer et al. 2001, Santema and Clutton-Brock 2013). Better survival and improved well-being of young ones may also result from better care because of the participation of individuals apart from the mother in rearing offspring (Moehlman 1979, Clutton-Brock et al. 2001, Meehan et al. 2016). The arrival, therefore, of young ones may have considerable effects on social structure and behaviour of social mammals, especially those that show fission-fusion dynamics, in which groups or subgroups can split or rejoin flexibly to change group size and composition in response to fluctuating ecological and social environments (Aureli et al. 2008). Such species may show regrouping, increasing group sizes and/or forming new associations in the presence of young ones, and increased sociality and cooperation, possibly because of the need for cooperative offspring care (see Lee 1987, Wells et al. 1987, Gero et al. 2013, Holmes et al. 2016, Marealle et al. 2020). Thus, studying the effect of young ones on adult grouping patterns and sociality would help us understand the extent to which social structure is shaped by their presence and associations with them. In this thesis, I attempted to understand the importance of young ones in female Asian elephant (Elephas maximus) society, collecting field data from Nagarahole and Bandipur National Parks and Tiger Reserves (Kabini elephant population) in southern India. Asian elephants are long-lived (Sukumar 2003), organised into matrilineal clans of mostly related females (Vidya and Sukumar 2005, Shetty 2016, Nandini et al. 2018), have a long period of dependency of young ones (Lahdenperä et al. 2016), and likely have a relatively low lifetime reproductive success. Thus, young ones are very valuable, and it has been suggested that cooperative care may be the raison d’être for female sociality in the Asian elephant (Gadgil and Nair 1984, Gadgil et al. 1985). I examined how the presence of calves (<1 year of age) affected female group sizes and associations, studied the development of various behaviours in calves and how calves interacted with various conspecific females, and then examined allomothering (care by non-mother females) and some reasons for such care. The thesis is organised as a set of manuscripts.