The social structure of a population is based on individual social associations, which can be described using network patterns (motifs). Our understanding of the forces stabilizing specific social structures in animals is limited. Structural balance theory was proposed for exploring social alliances and suggested that some network motifs are more stable than others in a society. The theory models the presence of specific triads in the network and their effect on the global population structure, based on the differential stability of specific triad configurations. While structural balance was shown in human social networks, the theory has never been tested in animal societies. Here we use empirical data from an animal social network to determine whether or not structural balance is present in a population of wild rock hyraxes, Procavia capensis. We confirm its presence and show the ability of structural balance to predict social changes resulting from local instability. We present evidence that new individuals entering the population introduce social instability, which counters the tendency of social relationships to seek balanced structures. Our findings imply that structural balance has a role in the evolution of animal social structure.
Bibliographical noteFunding Information:
We thank Andrew Edelman, Steven Goodreau, Rick Grannis, Mark S. Handcock and Tom A.B. Snijders for their helpful advice on ERGM analysis. We are obliged to our numerous field assistants and project students for their help with trapping the hyraxes, as well as to the nature reserve park rangers who supported the fieldwork. We thank the Nature and Parks Authority for permission to work in the Ein Gedi Nature Reserve, and the Ein Gedi Field School for their hospitality and logistic help. We thank Naomi Paz for editorial comments on the manuscript. We thank two anonymous referees for their comments, which immensely improved the manuscript. The Israel Sciences Foundation funded the study (grants 577/99 , 488/05 , 461/09 ). A.I. is a Postdoctoral Fellow at the National Institute for Mathematical and Biological Synthesis, an Institute sponsored by the National Science Foundation (NSF) , the U.S. Department of Homeland Security and the U.S. Department of Agriculture through NSF Award number EF-0832858, with additional support from the University of Tennessee, Knoxville.
- Network motif
- Procavia capensis
- Rock hyrax
- Social network
- Social structure
- Structural balance theory