Stereo video files used for 3d tracking horsefly trajectories

Of all hypotheses advanced for why zebras have stripes, avoidance of
biting fly attack receives by far the most support, yet the mechanisms by
which stripes thwart landings are not yet understood. A logical and
popular hypothesis is that stripes interfere with optic flow patterns
needed by flying insects to execute controlled landings. This could occur
through disrupting the radial symmetry of optic flow via the aperture
effect (i.e. generation of false motion cues by straight edges), or
through spatiotemporal aliasing (i.e. misregistration of repeated
features) of evenly spaced stripes. By recording and reconstructing
tabanid fly behaviour around horses wearing differently patterned rugs, we
could tease out these hypotheses using realistic target stimuli. We found
that flies avoided landing on, flew faster near, and did not approach as
close to striped and checked rugs compared to grey. Our observations that
flies avoided checked patterns in a similar way to stripes refutes the
hypothesis that stripes disrupt optic flow via the aperture effect, which
critically demands parallel striped patterns. Our data narrow the menu of
fly-equid visual interactions that form the basis for the extraordinary
coloration of zebras.