May I have your attention please you can now book your train tickets on Uber and get

10% back in credits to spend on your next Uber ride so you don't have to walk home in the brain again.

Trains now on Uber. T's and C's apply. Check the Uber app. Wherewolves aren't real. But stay with me for a moment.

Well, I tell you about the Werewolves aren't real. But stay with me for a moment,

while I tell you about the spade foot frogs,

specifically they're tadpoles,

which just might be the closest thing

to werewolves in nature.

I want to tell you about the bizarre and true story of

cannibal tadpoles. I'm Brian Gutierrez and this is Scientific Americans science

quickly. Spade-foot tadpoles are born as peaceful bottom feeders that eat little bits of algae and

poo floating in the water. But under the right conditions,

each tadpole has a chance to transform into a hulking agile predator. And the first thing on the

menu are other tadpoles.

And I have some right here.

I'm in the office of David Fenig,

on the third floor of the biology department

at the University of North Carolina at Chapel Hill.

So what you're seeing here is I'm showing you... at the University of North Carolina at Chapel Hill.

So what you're seeing here is I'm showing you a little vial filled with ethanol and it's got some

tadpoles in it and some of these tadpoles you see are small, some of the town poles you see are large.

Oh, okay, so this is one of the huge ones.

...