Kernel density estimates show data aggregated from an equal number of successful and unsuccessful constant-wind-direction plume tracking episodes (N time steps, E episodes). Plots reveal differences between the three behaviour modules across key behavioural measures: Head direction: head-direction densities are concentrated around ±180°, a signature of zig-zagging but mostly upwind movement. Angles are measured anticlockwise, with 0° indicating directly downwind. Density estimates for drift in the x direction (Δ x ) and y direction (Δ y ) per time step show how tracking is characterized by primarily upwind (negative x -direction) movement in both tracking and recover modules, but less so in the lost module. y -direction movements are notable in the tracking and recovering modules, corresponding to more complex turning behaviours, but minimal in the lost module. Turn action: left/right turning movements are balanced in the tracking module as the agent closely tracks the edge of the plume, but it is biased towards clockwise movements in the other two modules, especially the lost module. Move action: the agent substantially modulates its forward movement speed in the lost module only. Stray distance: the agent strays from the plume minimally in the tracking module, but substantially otherwise. Empirical distributions of course direction suggest that agents track the plume with respect to the plume centreline rather than the current wind direction.
