Caterpillars whistle to fend off attacking birds: Study

WASHINGTON - A new study has found that caterpillars can whistle to fend off attacking birds.

The walnut sphinx caterpillar, a type of moth larva, doesn’t whistle by puckering their lips and blowing, as they don’t have lips.

They blow out their sides, said researchers.

Jayne Yack at Carleton University in Ottawa revealed that walnut sphinx caterpillars (Amorpha juglandis) could toot from their sides.

Using high-speed video, the researchers noticed they pulled their heads back to compress the body cavity while they whistled. Unlike reptiles, birds and mammals, insects don’t breathe using their mouths, but with holes in their sides known as spiracles, and the scientists reasoned they were forcing air out these holes to whistle, generating squeaking noises.

Veronica Bura at Carleton University gently applied latex over all eight pairs of the caterpillars’ abdominal spiracles and then uncovered each pair systematically while pinching the larva.

The whistles definitely came from the eighth pair, generating trains of whistles lasting up to four seconds each, and spanning frequencies that ranged from those audible to birds and humans up to ultrasound.

The scientists put walnut sphinx caterpillars on twigs in cages with yellow warblers and patiently filmed the encounter. Surprisingly, when the birds attacked, the caterpillars whistled and the bird typically flinched and hopped or flew away. In tests with three warblers and two attacks each, the caterpillars got away completely unscathed.

“These birds are clearly startled by the unexpected sounds coming out of this caterpillar. They dove for cover,” Live Science quoted Yack as saying.

“The sounds are probably not advertising that the walnut sphinx caterpillars are distasteful. The birds simply appear to be startled, “because these sounds are unexpected,” added Yack.

The findings were reported in the Journal of Experimental Biology. (ANI)