ABSTRACT
The swinging of a mammal's tail has long been thought to deter biting insects, which, in cows, can drain up to 0.3 liters of blood per day. How effective is a mammal's tail at repelling insects? In this combined experimental and theoretical study, we filmed horses, zebras, elephants, giraffes and dogs swinging their tails. The tail swings at triple the frequency of a gravity-driven pendulum, and requires 27 times more power input. Tails can also be used like a whip to directly strike at insects. This whip-like effect requires substantial torques from the base of the tail on the order of 101–102 N m, comparable to the torque of a sedan, but still within the physical limits of the mammal. Based on our findings, we designed and built a mammal tail simulator to simulate the swinging of the tail. The simulator generates mild breezes of 1 m s–1, comparable to a mosquito's flight speed, and sufficient to deter up to 50% of mosquitoes from landing. This study may help us determine new mosquito-repelling strategies that do not depend on chemicals.
FOOTNOTES
Competing interests
The authors declare no competing or financial interests.
Author contributions
Conceptualization: D.H.; Methodology: D.H., M.E.M.; Software: M.E.M., Y.Z.; Formal analysis: M.E.M.; Investigation: M.E.M., K.C., Y.Z., M.B.; Data curation: M.E.M.; Writing - original draft: M.E.M.; Writing - review & editing: D.H.; Visualization: M.E.M.; Supervision: D.H.; Project administration: D.H.; Funding acquisition: D.H., M.E.M.
Funding
This research was funded by the Georgia Institute of Technology School of Biology and the Elizabeth Smithgall Watts endowment, and the National Science Foundation (career award PHY-1255127, and Graduate Research Fellowship DGE-1650044).
Supplementary information
Supplementary information available online at http://jeb.biologists.org/lookup/doi/10.1242/jeb.178905.supplemental
- Received February 7, 2018.
- Accepted July 16, 2018.
- © 2018. Published by The Company of Biologists Ltd
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