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The advantages of a high rank in the "game" of seduction

credits-F. Veronesi

An interdisciplinary study, recently published by Scientific Reports - Nature Publishing Group, has proposed a new territorial model for the formation of leks, the aggregations of animals where males compete with the purpose of being chosen as sexual partners by females. The study jointly combined the skills of physicists of complex systems and ethologists of the University of Milan, and involves Fabio Giavazzi, of the Department of Medical Biotechnology and Translational Medicine, Nicola Saino of the Department of Environmental Sciences and Policies and Alberto Vailati, of the Department of Physics.

In some animal species, such as the black grouse, the fallow deer and the bullfrog, during the breeding season male individuals gather in arenas called leks and compete to define a hierarchy. The competition takes place through the ritualized display of ornaments such as plumage, antlers, through vocalizations or olfactory traces. Once a hierarchy is established, high-ranking males are chosen as sexual partners from most of the females. Males of lower rank benefit from marginal reproductive opportunities determined by the large number of females who visit the lek. The question arises of what can be the advantages for a high-ranking male of copulating surrounded by a large number of individuals of lower rank.

The most important result of the study is that aggregation around high-ranking males leads to a significant reduction in the number of subordinate males competing directly with them, with potential socio-sexual benefits for high-ranking males resulting from the reduced competition. The comparison of the model with field data on populations of bustards shows that each lek is dominated by a few males of very high rank, indicating the presence of a pyramidal hierarchy.

In essence, high-ranking males in the lek thus benefit not only in terms of opportunities of access to a large number of females, but also of the privileged position that derives from the tendency of subordinate males to aggregate around high-ranking males.

Contacts:

Alberto Vailati,
Physics department,
alberto.vailati@unimi.it
02-50317339

Insights:

- Interview with A. Vailati during the radio broadcast "gli Sbandati", Radio2, 28/10/2018 (in Italian)

- Article on the newspaper "la Repubblica", 29/10/2018 (in Italian)

04 November 2018
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