Abstract
Analyses of animal social networks derived from group-based associations often rely on randomisation methods developed in ecology (Manly, Ecology 76:1109–1115, 1995) and made available to the animal behaviour community through implementation of a pair-wise swapping algorithm by Bejder et al. (Anim Behav 56:719–725, 1998). We report a correctable flaw in this method and point the reader to a wider literature on the subject of null models in the ecology literature. We illustrate the importance of correcting the method using a toy network and use it to make a preliminary analysis of a network of associations among eagle rays.
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Notes
Matrices of type A have 57 checkerboards, and matrices of type B have 51 checkerboards. Since there are 13 × 12/2 = 78 unordered pairs of individuals in our example, the C score of type A matrices is 57/78 = 0.7308, and the C score of type B matrices is 0.6538.
Each individual is assigned a prime number. For each group, i.e. each row in the matrix, a score is computed by multiplying the prime numbers of all individuals in this group. The score of a matrix is the sum of all row scores.
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Acknowledgements
JK acknowledges the financial support from the NERC and the EPSRC, and TG was supported by a Leverhulme fellowship. SK is grateful to Ralf Schiffer for some very useful initial discussions. We thank Herbert Krause for providing the drawing in Fig. 1.
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Communicated by Guest Editor D. Lusseau
This contribution is part of the special issue “Social Networks: new perspectives” (Guest Editors: J. Krause, D. Lusseau and R. James).
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Krause, S., Mattner, L., James, R. et al. Social network analysis and valid Markov chain Monte Carlo tests of null models. Behav Ecol Sociobiol 63, 1089–1096 (2009). https://doi.org/10.1007/s00265-009-0746-1
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DOI: https://doi.org/10.1007/s00265-009-0746-1