Tuesday, 10 February 2015

Spotlights flip the switch on an evolutionary arms race

When lights go on, moths drop their guard against predatory bats.
06 February 2015

Flip on a light in the middle of the night and the average kitchen cockroach or mouse will scurry away. In the same situation, however, some species of moth tend to drop their defences and end up as a bat’s lunch.

Bats and moths have been evolving to one-up each other for 65 million years. Many moths can hear bats’ ultrasonic echolocation calls, making it easy for the insects to avoid this predator. A few species of bat have developed calls that are outside the range of the moths’ hearing, making it harder for the moths to evade them1. But humans short-circuit this evolutionary arms race every time they turn on a porch light, according to a study in the Journal of Applied Ecology2.

In field experiments, ecologist Corneile Minnaar of the University of Pretoria and his colleagues examined the diet of Cape serotine bats (Neoromicia capensis) both in the dark and under artificial light in a national park near Pretoria. The bat, an insect-eating species common in South Africa, has an echolocation call that moths can hear. Minnaar and his team determined both the species and quantity of available insect prey at the test sites using a hand-held net and a stationary trap.

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