Glass act: Scientists reveal secrets of frog transparency

WASHINGTON (AP) — Now you see them, now you don’t.

Some frogs found in South and Central America have the rare ability to turn on and off their nearly transparent appearance, researchers report Thursday in the journal Science.

During the day, these nocturnal frogs sleep by hanging underneath tree leaves. Their delicate, greenish transparent forms don't cast shadows, rendering them almost invisible to birds and other predators passing overhead or underneath.

But when northern glass frogs wake up and hop around in search of insects and mates, they take on an opaque reddish-brown color.