Goat breath causes aphids to drop to the ground
Some headlines just write themselves…
It has been known for some time that an approaching large herbivore causes aphids to abandon ship …err plant. Makes sense since, after all, there’s not much of a point in staying on the particular bit of shrubbery that will be consumed, lock, stalk and barrel by a ravenous forager. However, it was not exactly clear what in the herbivore causes the aphids to drop. Well, it is not the shaking of the twigs, as rustling the plant did not cause a substantial number of the aphids to drop. Rather, it’s the breath. The researchers had a human, a sheep and goat all breath on an aphid-infested plant, with equal results: the aphids dropped from the plant en-masse. But what in the breath causes aphids to do that? Well, it is not the CO2 nor the air movement itself. Rather, the heat and the humidity of the breathing, as tested by Moshe Gish and his colleagues at the University of Haifa.
This is a great example of adaptation: after all, bush movement may be due to many different factors, including uninterested rodents and carnivores. Also, air movement can be simply caused by wind, including hot or humid air. But someone breathing directly on you, hot and damp can only mean one thing to an aphid: abandon plant or be goat dinner!
Moshe Gish, Amots Dafni, & Moshe Inbar (2010). Mammalian herbivore breath alerts aphids to flee host plant Current Biology, 20 (15) R628-R629
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