Caterpillar whistling – it's a thing. In fact, it has been for quite some time. Back in 2010 (how did I miss this?) scientists at Canada's Carlton University discovered that walnut sphinx moth (Amorpha juglandis) caterpillars had a special affinity for squeaking. The sound you hear comes from the caterpillar forcing air out of small holes in its sides (called spiracles).

To find out the reason for these 'tiny tunes', the researchers housed walnut sphinx moth caterpillars with yellow warblers (birds known to eat the caterpillars). When the birds attacked, the whistles often caused the avian predators to flinch or fly away. So it looks like the Namaqua rain frog isn't the only animal defending itself with the almighty 'squee'!

h/t Charles Choi