Fig. 7.

Predictions of release-and-recapture data using advection–diffusion model. Each panel plots normalized probability density functions for values of w_traj and g_traj predicted from simulations of the advection–diffusion equation over a circular domain representing the release site and circular trap array (SI Appendix). (A) Simulation results (gray density) compared to field data (points) for the release experiment performed with traps at 250 m (Fig. 3). The results shown are based on the measured wind conditions after applying a Gaussian kernel. The value of the diffusion coefficient that resulted in the best fit with the field data was 70 m² · s⁻¹. The inset shows the metric for the fit (log Bayes factor) as a function of different diffusion coefficients. The model is particularly bad at predicting the data generated by flies flying upwind (w_traj < 0) at their preferred groundspeed (w_traj ∼1). (B) As in A but for the complete set of trap data collected at 1 km. As in our agent-based simulations (Fig. 6 E–H), these simulations used a composite of windspeeds measured during all five experiments. In the 1 km case, the data were best fit by a diffusion coefficient of 300 m² · s⁻¹.