Friday, February 10, 2012

Finding connections

What is the connection between these?
 
Zebras (Sparks4 / Wikimedia Commons)



Horsefly - Tabanidae (Shyamal / Wikimedia Commons)

For inspirations/clues see Kipling's Just So Stories ... (Read book Online)

Well, it seems that the stripes keep away biting flies, particularly Tabanidae. A recent study that made use of sticky horse models with different colour patterns has determined that having white stripes breaks up the dark areas that reflect polarized light that attracts the tabanids. I am not sure about the physics but apparently dark surfaces polarize reflections more that white surfaces. Interestingly this is not the first research to suggest that zebra stripes had something to do with keeping away flies. It had already been suggested in 1981.


The new research however has caught much more attention, including the folks at ignobel.

Some useful extra reading is - György Kriska, Balázs Bernáth, Róbert Farkas, Gábor Horváth (2009) Degrees of polarization of reflected light eliciting polarotaxis in dragonflies (Odonata), mayflies (Ephemeroptera) and tabanid flies (Tabanidae). Journal of Insect Physiology 55(12):1167-1173. I have seen dragonflies and certain Hesperiids going after cars with black sunfilm on their rear windscreens and this may well be related to polarized reflections. Interestingly it seems the moon surface is so rough that it depolarizes light that it reflects! Read also this article on how humans interfere with animal perception even with eco-friendly solar panels.

References



2 comments:

  1. Hmm...what about all those theories then of "disruptive coloration" of the zebra giving it some advantage in confusing predators as to which "direction" they are running? (Based on what I read about work from Thayer and his ilk in Dazzled and Deceived - see http://www.daktre.com/2012/02/294/)

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  2. http://en.wikipedia.org/wiki/Abbott_Handerson_Thayer Thayer was creative indeed!

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