Why don't horseflies land on zebras?

Tim Caro*, Eva Fogg, Tamsin Stephens-Collins, Matteo Santon, Martin J How

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

1 Citation (Scopus)

Abstract

Stripes deter horseflies from landing on zebras and, while several mechanisms have been proposed, these hypotheses have yet to be tested satisfactorily. Here, we investigated three possible visual mechanisms that could impede successful tabanid landings (aliasing, contrast, polarization and additionally explored pattern element size) employing video footage of horseflies around differently patterned coats placed on domestic horses. We found that horseflies are averse to landing on highly but not on lightly contrasting stripes printed on horse coats. We could find no evidence for horseflies being attracted to coats that better reflected polarized light. Horseflies were somewhat less attracted to regular than to irregular check patterns, but this effect was not large enough to support the hypothesis of disrupting optic flow through aliasing. More likely it is due to attraction towards larger dark patches present in the irregular check patterns, an idea bolstered by comparing landings to the size of dark patterns present on the different coats. Our working hypothesis is the principal anti-parasite features of zebra pelage are that their stripes are sharply outlined and thin because these features specifically eliminate the occurrence of large monochrome dark patches that are highly attractive to horseflies at close distances.
Original languageEnglish
Article numberjeb244778
Number of pages7
JournalJournal of Experimental Biology
Volume226
Issue number4
DOIs
Publication statusPublished - 17 Feb 2023

Bibliographical note

Funding Information:
M.J.H. thanks the Royal Society for funding (URF/R/201021). Open access funding provided by University of Bristol. Deposited in PMC for immediate release.

Publisher Copyright:
© 2023. Published by The Company of Biologists Ltd.

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