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Fission-Fusion dynamics in the social networks of a North American pitviper

Tetzlaff, Sasha J.

Ecological Processes Branch

US Army Construction Engineering Research Laboratory

Champaign, Illinois USA

Illinois Natural History Survey, Prairie Research Institute

University of Illinois Urbana-Champaign

Champaign, Illinois USA

Vizentin-Bugoni, Jeferson

Programa de Pós-Graduação em Biologia Animal,

Instituto de Biologia, Universidade Federal de Pelotas, RS, Brazil

Sperry, Jinelle H.

U.S. Army Corps of Engineers

Engineer Research Development Center

Champaign, Illinois USA

Department of Natural Resources and Environmental Sciences

University of Illinois at Urbana-Champaign

Urbana, Illinois USA

Davis, Mark A.

Illinois Natural History Survey, Prairie Research Institute

University of Illinois Urbana-Champaign

Champaign, Illinois USA

Clark, Rulon W.

Department of Biology, San Diego State University

San Diego, California USA

Chiricahua Desert Museum

Rodeo, New Mexico USA

Repp, Roger A.

National Optical Astronomy Observatory (NOAO)

Tucson, Arizona USA

Schuett, Gordon W.

Department of Biology ǀ Neuroscience Institute

Georgia State University

Atlanta, Georgia USA

Chiricahua Desert Museum

Rodeo, New Mexico USA

Social network ecology is a powerful conceptual and analytical framework for identifying group-level interaction patterns of and contributions by individuals. We examined the structure of social networks for adult western diamond-backed rattlesnakes (Crotalus atrox) in Arizona, USA using long-term (>10 years) data to determine if group-level patterns emerged in network structures for three types of social interactions: denning, pairing, and parentage. We also investigated whether body length, sex, and home range size were predictive of individuals’ centrality (i.e., individual importance for group connectivity) in each of the three networks. Of 191 genotyped adults, a subset of 50 snakes (28 females, 22 males) were radio-tracked from 2001–2010. We found the three networks were structurally modular (i.e., formed distinct clusters of individuals interacting). Sex was the only significant predictor of centrality in the parentage network, with females slightly more connected than males, likely due to high levels of multiple mating, long-term sperm storage, and resultant multiple paternity. Interacting telemetered snakes were unlikely to be related in any of the three networks. Despite ample opportunities to interact with numerous conspecifics that had highly overlapping spring-summer home ranges, individuals tended to interact with limited partners, which also differed from individuals they associated with at communal dens during winter. Thus, our results show strong seasonal fission-fusion dynamics exist in this C. atrox population. Furthermore, although both sexes show high annual fidelity to both home ranges and communal dens, females occasionally alter den sites and overwinter privately in mammal nests or burrows, indicative of active manipulation of their social environment. We illustrate that comprehensive and long-term datasets incorporating social network analysis with spatial and genetic information provide robust and unique insights to understanding social structure of understudied secretive taxa such as pitvipers.


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