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Author Sundaresan, S.R.; Fischhoff, I.R.; Dushoff, J.; Rubenstein, D.I.
Title Network metrics reveal differences in social organization between two fission-fusion species, Grevy's zebra and onager Type Journal Article
Year 2007 Publication (down) Oecologia Abbreviated Journal Oecologia
Volume 151 Issue 1 Pages 140-149
Keywords Analysis of Variance; Animals; Behavior, Animal/*physiology; *Environment; Equidae/*physiology; Female; India; Kenya; Male; *Models, Theoretical; *Social Behavior; *Social Environment
Abstract For species in which group membership frequently changes, it has been a challenge to characterize variation in individual interactions and social structure. Quantifying this variation is necessary to test hypotheses about ecological determinants of social patterns and to make predictions about how group dynamics affect the development of cooperative relationships and transmission processes. Network models have recently become popular for analyzing individual contacts within a population context. We use network metrics to compare populations of Grevy's zebra (Equus grevyi) and onagers (Equus hemionus khur). These closely related equids, previously described as having the same social system, inhabit environments differing in the distribution of food, water, and predators. Grevy's zebra and onagers are one example of many sets of coarsely similar fission-fusion species and populations, observed elsewhere in other ungulates, primates, and cetaceans. Our analysis of the population association networks reveals contrasts consistent with their distinctive environments. Grevy's zebra individuals are more selective in their association choices. Grevy's zebra form stable cliques, while onager associations are more fluid. We find evidence that females associate assortatively by reproductive state in Grevy's zebra but not in onagers. The current approach demonstrates the utility of network metrics for identifying fine-grained variation among individuals and populations in association patterns. From our analysis, we can make testable predictions about behavioral mechanisms underlying social structure and its effects on transmission processes.
Address Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA. ssundare@princeton.edu
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0029-8549 ISBN Medium
Area Expedition Conference
Notes PMID:16964497 Approved no
Call Number Serial 1863
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Author Fischhoff, I.; Dushoff, J.; Sundaresan, S.; Cordingley, J.; Rubenstein, D.
Title Reproductive status influences group size and persistence of bonds in male plains zebra (Equus burchelli) Type Journal Article
Year 2009 Publication (down) Behavioral Ecology and Sociobiology Abbreviated Journal Behav. Ecol. Sociobiol.
Volume 63 Issue 7 Pages 1035-1043-1043
Keywords Biomedical and Life Sciences
Abstract Animal groups arise from individuals’ choices about the number, characteristics, and identity of associates. Individuals make these choices to gain benefits from their associations. As the needs of an individual change with its phenotype, so too we expect the nature of its associations to vary. In this paper, we investigate how the social priorities of male plains zebra (Equus burchelli) depend on reproductive state. An adult male is either a bachelor, and lacking mating access, or a stallion defending a harem. Multiple harems and bachelor males aggregate in larger herds. Herds frequently split and merge, affording males opportunities to change associates. Over a 4-year period, we sampled the herd associations in a population of 500–700 zebras. To isolate the effects of reproductive state on male social behavior, we account for potential confounding factors: changes in population size, grouping tendencies, and sampling intensity. We develop a generally applicable permutation procedure, which allows us to test the null hypothesis that social behavior is independent of male status. Averaging over all individuals in the population, we find that a typical bachelor is found in herds containing significantly more adults, bachelors, and stallions than the herds of a typical stallion. Further, bachelors’ bonds with each other are more persistent over time than those among stallions. These results suggest that bachelors form cohesive cliques, in which we may expect cooperative behaviors to develop. Stallion–stallion associations are more diffuse, and less conducive to long-term cooperation.
Address
Corporate Author Thesis
Publisher Springer Berlin / Heidelberg Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0340-5443 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Equine Behaviour @ team @ Serial 5193
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