Dynamics on the Spider Web - Predictive Physics-Based Model for Mating Interactions in Spiders

  Amir Haluts [1]  ,  Sylvia F. Garza [2]  ,  Alex L. Jordan [2]  ,  Nir Gov [1]  
[1] Weizmann Institute of Science
[2] Max Planck Institute of Animal Behavior, Konstanz, Germany

In the orb-weaving spider Nephila clavipes, females build large 2-dimensional webs, to which mature males migrate in order to mate with the females. Female webs thus serve as isolated interaction arenas, in which male-female and male-male interactions take place. To minimize the pre-mating risks posed by females, males exhibit non-trivial dynamics in their motion on the web. The activity of males in female webs is further governed by inter-male competition. In many cases, multiple males are found to occupy the same female's web and compete with each other for mating opportunities, displaying various levels of aggression to-wards rivals. The predominant modality of communication in this system is vibratory signals, which propagate through the elastic surface of the web. This unique feature makes the interac-tions physical in nature, and therefore amenable to physics-based modeling.

In this work we present a predictive physics-based model for the mating-related dynamics of N. clavipes males in a female's web. In collaboration with Alex Jordan's group (Max Planck Institute, Konstanz, Germany) we obtained new dynamical data regarding male-female and male-male interactions in N. clavipes from controlled experiments. We applied a systematic physics-based approach and constructed a theoretical mean-field model that reliably reduces the interactions to effective potentials. We present extensive simulation results that establish the validity of our model in reproducing the essential dynamical properties of this system. We further show that ecological predictions, such as male competition outcomes in various realistic scenarios, can be generated from the underlying effective physics captured by our model.