Stochastic model description

Here we formulate a model that is based on the persistant turning walker (PTW) model \cite{Gautrais_2008,Gautrais_2012}, an extension to this model that includes changes in speed \cite{Zienkiewicz_2014}.  We use this framework and adapt the zonal model of collective movement \cite{COUZIN_2002,Ioannou_2012,Couzin_2005}  to simulate using the PTW equations, and incorporate a zonal rule for individuals to adjust their speed based on social interactions.  We simulated this model in different cases, which correspond to pairs of parasitized and non-parasitized fish swimming together, to ask if observed differences in behavior are due to different social responses, or simply due to different swimming abilities.  We show that apparent differences in social behavior can be explained simply by physical differences in turning inertia and acceleration speeds.

Stochastic model and parameter selection