Franco Bagnoli - Università di Firenze #
Ant warfare: modeling battles among social animals #
The aim of our study is to develop an original approach to the modeling of battle 
dynamics among social animals. We focus on ant behavior, for a variety of reasons. 
Ants represent an important environmental actor, exhibit extraordinary strategies used 
to achieve their ecological success, and are individually "simple" to be 
studied in laboratory. Moreover, modeling ant warfare has a direct application to the 
monitoring of invasive species. An invasive ant species become dominant through an 
extraordinary cooperative behavior, an aspect of which is represented by the 
strategies adopted during the wars against other species. Our studies focused on two 
species with different fighting strategies: the invasive Lasius neglectus and the 
autochthonous Lasius paralienus. We performed several in vitro experiments, with a 
small number of ants in a limited environment (Petri dish) due to observational 
limits. These experiments represent the validating framework of the models developed. 
We started by assuming the absence of any cognitive strategy, applying the classical 
"chemical modeling", where all the interactions among members of the system 
are represented following the formalism used to represent chemical reactions. The 
proposed chemical model considers the ant individuals and fighting groups equivalent 
to atoms and molecules. We identified a system of differential non-linear equations, 
taking into consideration the observed groups. To reproduce the stochastic 
fluctuations of the observed data and to generate realistic trajectories, we 
considered two agent-based stochastic models, with and without a spatial distribution. 
With respect to other war models, our chemical model considers all phases of the 
battle and not only casualties. One more advantage of this approach is that all 
possible interactions can be outlined using a simple but biologically meaningful 
formalism, which provide a "microscopic" (i.e., at the individual level) 
description of the system, in contrast with the "macroscopic" population level 
description provided by classical models like Lanchester's ones. Finally, assuming 
that our model is a good description of the real interspecies interactions, and 
studying battles among more species, we can address the problem of deriving the 
chemical parameters from a smaller number of species-specific parameters (like 
aggressiveness, strength, cooperation, resistance, etc.). The possibility to have a 
scalable way of investigating animal fights (that may involve thousands of 
individuals) may have deep consequences in predicting the outcome of real combats and 
an important tool in predicting the successfulness of invasive species.