Controlling for behavioural state reveals social dynamics among male African elephants, Loxodonta africana

The drivers of social affiliation may vary over time as individuals change their goals with respect to changing environments or physical condition. Studies of companion preference rarely consider shifts in motivational state, despite the potential importance of such shifts in structuring association and population processes. Ignoring state dependence in social behaviour may weaken the ability to recognize social properties and identify their underlying drivers. Modifying established approaches, we apply a state-specific analysis to investigate social properties in male African elephants, which are thought to be weakly social. Specifically, we delineate associations during distinct sexually active and inactive periods and quantify common social metrics (network size, density, betweenness and the number and age of preferred companions) to examine how sexual states may relate to male elephant social relationships. We found that state-dependent association index values were higher and quantitative definitions of preferred companions were more conservative than those derived when sexual state was not taken into account. Preferred companions tended to be closer in age among sexually inactive dyads relative to sexually active dyads, indicating that bulls seek out age-mates when sexually inactive. Networks were larger and denser when sexually inactive. By accounting for dynamic behaviour in social systems, this study demonstrates that male African elephants show more social preference than had been previously thought.

[1]  Steven D. Prager,et al.  The dynamics of animal social networks: analytical, conceptual, and theoretical advances , 2014 .

[2]  L. Bejder,et al.  A method for testing association patterns of social animals , 1998, Animal Behaviour.

[3]  H. Hofer,et al.  Male spotted hyenas (Crocuta crocuta) queue for status in social groups dominated by females , 2001 .

[4]  W. Getz,et al.  The socioecology of elephants: analysis of the processes creating multitiered social structures , 2005, Animal Behaviour.

[5]  J. Beacham Models of Dominance Hierarchy Formation: Effects of Prior Experience and Intrinsic Traits , 2003 .

[6]  Lars Bejder,et al.  Testing association patterns: issues arising and extensions , 2005, Animal Behaviour.

[7]  G. Wittemyer,et al.  A Comparison of Social Organization in Asian Elephants and African Savannah Elephants , 2012, International Journal of Primatology.

[8]  S. Durant,et al.  Matriarchs As Repositories of Social Knowledge in African Elephants , 2001, Science.

[9]  Peter K. McGregor,et al.  Analyzing Animal Societies: Quantitative Methods for Vertebrate Social Analysis , 2009 .

[10]  C. Garroway,et al.  Do social networks of female northern long-eared bats vary with reproductive period and age? , 2010, Behavioral Ecology and Sociobiology.

[11]  T. Rowell The concept of social dominance. , 1974, Behavioral biology.

[12]  Bryan F. J. Manly,et al.  A Note on the Analysis of Species Co‐Occurrences , 1995 .

[13]  Kevin E. Langergraber,et al.  From the Cover : The limited impact of kinship on cooperation in wild chimpanzees , 2007 .

[14]  M. Dludlu Musth in the African elephant, Loxodonta africana. , 1984 .

[15]  Matthieu Latapy,et al.  Computing Communities in Large Networks Using Random Walks , 2004, J. Graph Algorithms Appl..

[16]  Reproductive status influences group size and persistence of bonds in male plains zebra (Equus burchelli) , 2009, Behavioral Ecology and Sociobiology.

[17]  George Wittemyer,et al.  Breeding phenology in relation to NDVI variability in free‐ranging African elephant , 2007 .

[18]  Cynthia J. Moss,et al.  Musth in the African elephant, Loxodonta africana , 1981, Nature.

[19]  M. Newman,et al.  Identifying the role that animals play in their social networks , 2004, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[20]  George Wittemyer,et al.  Poaching policy: Rising ivory prices threaten elephants , 2011, Nature.

[21]  D. Lusseau Why Are Male Social Relationships Complex in the Doubtful Sound Bottlenose Dolphin Population? , 2007, PloS one.

[22]  R. Connor,et al.  Complex social structure, alliance stability and mating access in a bottlenose dolphin ‘super-alliance’ , 2001, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[23]  W. Hamilton Geometry for the selfish herd. , 1971, Journal of theoretical biology.

[24]  J. Poole Mate guarding, reproductive success and female choice in African elephants , 1989, Animal Behaviour.

[25]  Lawrence R. Rabiner,et al.  A tutorial on hidden Markov models and selected applications in speech recognition , 1989, Proc. IEEE.

[26]  F. Gill,et al.  Economics of Feeding Territoriality in the Golden-Winged Sunbird , 1975 .

[27]  G. Wittemyer,et al.  Estimating age of immobilized elephants from teeth impressions using dental silicon , 2005 .

[28]  C. Moss The demography of an African elephant (Loxodonta africana) population in Amboseli, Kenya , 2001 .

[29]  M E J Newman,et al.  Modularity and community structure in networks. , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[30]  H. Croze The Seronera bull problem: The elephants , 1974 .

[31]  J. Poole,et al.  Male Social Dynamics: Independence and Beyond , 2011 .

[32]  Bette A. Loiselle,et al.  It takes two to tango: reproductive skew and social correlates of male mating success in a lek-breeding bird , 2009, Proceedings of the Royal Society B: Biological Sciences.

[33]  R. Bon,et al.  Sociality and relationships in Alpine ibex (Capra ibex) , 1998, Revue d'Écologie (La Terre et La Vie).

[34]  S. Emlen,et al.  Ecology, sexual selection, and the evolution of mating systems. , 1977, Science.

[35]  N. Mantel The detection of disease clustering and a generalized regression approach. , 1967, Cancer research.

[36]  G. A. Sonerud,et al.  Ignorant hooded crows follow knowledgeable roost-mates to food: support for the information centre hypothesis , 2001, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[37]  L. Vigilant,et al.  Social Bonds Enhance Reproductive Success in Male Macaques , 2010, Current Biology.

[38]  I. Douglas‐Hamilton On the ecology and behaviour of the African elephant , 1972 .

[39]  Richard James,et al.  Hypothesis testing in animal social networks. , 2011, Trends in ecology & evolution.

[40]  C. Ryer,et al.  Social enhancement of foraging on an ephemeral food source in juvenile walleye pollock, Theragra chalcogramma , 1991, Environmental Biology of Fishes.

[41]  H. B. Rasmussen,et al.  The sexually active states of free-ranging male African elephants (Loxodonta africana): defining musth and non-musth using endocrinology, physical signals, and behavior , 2005, Hormones and Behavior.

[42]  R Core Team,et al.  R: A language and environment for statistical computing. , 2014 .

[43]  George Wittemyer,et al.  Comparative Demography of an At-Risk African Elephant Population , 2013, PloS one.

[44]  I. Douglas‐Hamilton,et al.  Endocrine and behavioral changes in male African elephants: Linking hormone changes to sexual state and reproductive tactics , 2008, Hormones and Behavior.

[45]  A. V. Jaarsveld,et al.  Patterns of coalition formation and spatial association in a social carnivore, the African wild dog (Lycaon pictus) , 2003 .

[46]  G. Wittemyer,et al.  Demographic status of elephants in the Samburu and Buffalo Springs National Reserves, Kenya , 2005 .

[47]  Anna Dornhaus,et al.  Time-Ordered Networks Reveal Limitations to Information Flow in Ant Colonies , 2011, PloS one.

[48]  C. Schaik,et al.  Male Bonds: Afilliative Relationships Among Nonhuman Primate Males , 1994 .

[49]  Steven J. Schwager,et al.  A comparison of association indices , 1987, Animal Behaviour.

[50]  J. Poole Rutting Behavior in African Elephants: the Phenomenon of Musth , 1987 .

[51]  David Lusseau,et al.  A killer whale social network is vulnerable to targeted removals , 2006, Biology Letters.

[52]  Truman P. Young,et al.  Measuring association between individuals or groups in behavioural studies , 1992, Animal Behaviour.

[53]  S. Harris,et al.  Adolescence in male African elephants, Loxodonta africana, and the importance of sociality , 2008, Animal Behaviour.

[54]  A. Hall-Martin Role of musth in the reproductive strategy of the African elephant ( Loxodonta a / ricana ) , 2010 .

[55]  H. Gerhardt,et al.  Sexual Parasitism in the Green Tree Frog (Hyla cinerea) , 1978, Science.

[56]  Jean Thioulouse,et al.  ADE-4: a multivariate analysis and graphical display software , 1997, Stat. Comput..

[57]  Stanley Wasserman,et al.  Social Network Analysis: Methods and Applications , 1994, Structural analysis in the social sciences.

[58]  J. Poole,et al.  Leadership in elephants: the adaptive value of age , 2011, Proceedings of the Royal Society B: Biological Sciences.

[59]  G. Wittemyer The elephant population of Samburu and Buffalo Springs National Reserves, Kenya , 2001 .

[60]  R. Bon,et al.  Segregation is not only a matter of sex in Alpine ibex, Capra ibex ibex , 2001, Animal Behaviour.

[61]  J. Poole,et al.  Association patterns of African elephants in all-male groups: the role of age and genetic relatedness , 2011, Animal Behaviour.