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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2006.10.008 Byline: G. Wittemyer, W.M. Getz Abstract: According to the socioecological framework, transitivity (or linearity) in dominance relationships is related to competition over critical resources. When a population is structured into groups, the intensity of between- versus within-group competition influences the form and function of its social organization. Few studies have compared the type and relative intensity of competition at these two levels. African elephants have well-structured social relations, providing an exemplary system for such a study. We report on dominance hierarchies among free-ranging elephants and evaluate the factors that drive their socioecological structure to lie in a region of the three-dimensional nepotism/despotism/tolerance space rarely observed among social species; namely, where non-nepotistic, transitive dominance hierarchies within groups emerge despite kin-based philopatry and infrequent agonistic interactions over widely distributed resources. We found significant transitivity in dominance hierarchies between groups. Dominance relations among the matriarchs of different social groups were primarily age based, rather than driven by physical or group size, and group matriarch rank influenced the dominance relationships among nonmatriarchal females in the population. Our results suggest that between-group dominance relationships induce tolerance among group members, which in combination with high group relatedness, reduces the benefits of nepotism. We postulate that cognitive abilities and high risk of injury in contests enhance winner and loser effects, facilitating the formation of transitive dominance relationships, despite widely distributed resources over which infrequent competition occurs. The interplay of cognitive abilities, winner and loser effects, resource distribution, and within- and between-group dominance relationships may produce behaviour in other strongly social mammals that differs from that predicted by a superficial application of current socioecological models. Author Affiliation: (a) Department of Environmental Science, University of California, Berkeley, CA, U.S.A. (a ) Save the Elephants, Nairobi, Kenya Article History: Received 6 June 2006; Revised 26 August 2006; Accepted 12 October 2006 Article Note: (miscellaneous) MS. number: A10467R more...

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2004.08.018 Byline: G. Wittemyer, I. Douglas-Hamilton, W.M. Getz Abstract: In this paper, we investigate the formation and function of the multilevelled, fission-fusion social structure in a free-ranging African elephant, Loxodonta africana, population. We quantitatively identified the existence of four social tiers by using cluster analysis on individual association data. We assessed the effects of season and study period on social structuring and levels of cohesion within and among social units. We found that second-tier units, potentially the equivalent of the 'family', were stable across seasonal periods but the number of units increased as the study progressed and the population grew. It appears that these units were sufficiently small not to be influenced by ecologically related factors, such as resource competition, that might otherwise lead to them splitting. On the other hand, third- and fourth-tier units were significantly affected by season in a way that suggests a trade-off between ecological costs (e.g. from resource competition) and different social and ecological benefits (e.g. from predator defence, territoriality, knowledge sharing and rearing of young). Age structure also appeared to influence this multitiered social organization. The size of second-tier social units was significantly affected by the age of matriarchs: units lead by matriarchs likely to be grandmothers (i.e. females 35 years and older) were significantly larger than those lead by younger matriarchs. We present a conceptual framework for understanding the emergence of multiple-tier social structure from interactions driven by socioecological processes. This study is the first to use rigorous quantitative methods to statistically show the existence of four hierarchical tiers of social organization in a nonhuman animal. Additionally, our results elucidate the role that ecological processes play in producing complex social structures. Author Affiliation: (*) Department of Environmental Science, Policy and Management, University of California, Berkeley, U.S.A. (a ) Save the Elephants, Kenya (a ) Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, South Africa Article History: Received 17 June 2004; Revised 23 July 2004; Accepted 18 August 2004 Article Note: (miscellaneous) MS. number: A9821 more...

Genotyping errors and successes were assessed via 20 microsatellite loci drawn from fresh dung samples for the African savannah elephant. Low errors and high successes show the dependability of the simple pedigree method in noninvasive studies. more...