Caro, Tim

Gonzales, Dunia

How, Martin J

Irwin, Alison

English

Of all hypotheses advanced for why zebras have stripes, avoidance ofbiting fly attack receives by far the most support, yet the mechanisms bywhich stripes thwart landings are not yet understood. A logical and popularhypothesis is that stripes interfere with optic flow patterns needed by flyinginsects to execute controlled landings. This could occur through disruptingthe radial symmetry of optic flow via the aperture effect (i.e. generation offalse motion cues by straight edges), or through spatio-temporal aliasing(i.e. misregistration of repeated features) of evenly spaced stripes. By recordingand reconstructing tabanid fly behaviour around horses wearingdifferently patterned rugs, we could tease out these hypotheses using realistictarget stimuli. We found that flies avoided landing on, flew faster near,and did not approach as close to striped and checked rugs compared togrey. Our observations that flies avoided checked patterns in a similarway to stripes refutes the hypothesis that stripes disrupt optic flow via theaperture effect, which critically demands parallel striped patterns. Ourdata narrow the menu of fly-equid visual interactions that form the basisfor the extraordinary coloration of zebras

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Zebra stripes, tabanid biting flies and the aperture effect

https://research-information.bris.ac.uk/files/246843415/rspb.2020.1521.pdf

Zebra stripes, tabanid biting flies and the aperture effect

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