Abstract
In conflicts between social groups, the decision of competitors whether to attack/retreat should be based on the assessment of the quantity of individuals in their own and the opposing group. Experimental studies on numerical cognition in animals suggest that they may represent both large and small numbers as noisy mental magnitudes subject to scalar variability, and small numbers (≤4) also as discrete object-files. Consequently, discriminating between large quantities, but not between smaller ones, should become easier as the asymmetry between quantities increases. Here, we tested these hypotheses by recording naturally occurring conflicts in a population of free-ranging dogs, Canis lupus familiaris, living in a suburban environment. The overall probability of at least one pack member approaching opponents aggressively increased with a decreasing ratio of the number of rivals to that of companions. Moreover, the probability that more than half of the pack members withdrew from a conflict increased when this ratio increased. The skill of dogs in correctly assessing relative group size appeared to improve with increasing the asymmetry in size when at least one pack comprised more than four individuals, and appeared affected to a lesser extent by group size asymmetries when dogs had to compare only small numbers. These results provide the first indications that a representation of quantity based on noisy mental magnitudes may be involved in the assessment of opponents in intergroup conflicts and leave open the possibility that an additional, more precise mechanism may operate with small numbers.
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Acknowledgments
We are deeply indebted to Christian Agrillo who provided fundamental suggestions and relevant literature. We also would like to thank Annamaria Andreozzi and Mirella De Paolis for helping with the dog census; Mario Di Traglia, Alessandro Giuliani and Orazio Rossi for statistical advices; Oliver P. Hoener for providing long stimulating discussions about territoriality and the methods for assessing it; Gina Raihani and Marion L. East for language revision; Rolf O. Peterson and Manuela Piazza for providing useful literature; the three anonymous referee whose suggestions greatly improved the manuscript. A special thank goes also to Luis Nieder who provided support and facilities. Finally, this research was partially funded by University of Parma with FIL 2005 and FIL 2006 to Paola Valsecchi, and it complies with all laws of the country (Italy) in which it was performed.
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Bonanni, R., Natoli, E., Cafazzo, S. et al. Free-ranging dogs assess the quantity of opponents in intergroup conflicts. Anim Cogn 14, 103–115 (2011). https://doi.org/10.1007/s10071-010-0348-3
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DOI: https://doi.org/10.1007/s10071-010-0348-3