Eating The Poisonous Mushroom

Who's going next? asks Graceful.

Me, says the second ninja. Imagine you're alone in the jungle, and you've eaten a poisonous mushroom.

That's not a riddle, says Terence.

I've not finished asking, says the second ninja.

No talking! says Graceful.

Meaning me? asks second ninja.

No, you keep going, says Graceful. I like the start of this riddle.

You know there is only one antidote, says second ninja. A female frog secretion. 

Yuck, says Terence. 

Hush!says Graceful.

You enter a clearing, and see a frog on a log. Is it a female? You have no idea. 

Unless you're another frog, says Gaius. Are we to assume you're a human?

In this riddle, yes, says second ninja.

Go and lick it, says Terence.

You are about to, says second ninja, when you hear a croak from behind. On a log sit two frogs and one of them has done the croaking. Therefore you know one of these two is a male. 

Why is it? asks Terence.

Only males croak, says second ninja.

Pretty much true, says Letitia.

You feel faint, says the second ninja. You must lick a female or die.

Exciting, isn't it! says Graceful.

I dont know, says Katherine.  Where is this going?

Conditional probability, says Wittgenstein.

You only have time to go one way or the other, says the second ninja. To the rock or the log. Which way do you go?

Log, says Terence.

Not so fast, says second ninja. First you must calculate your chances.

Fifty-fifty, guesses Katherine.

Only for the one on the rock, says Wittgenstein. Not for the other. Remember you have one extra piece of information.

The croak, saus Gaius. Therefore the ones on the log can't be both female.

Therefore what are the remaining possibilities? asks Wittgenstein.

Too late, says the second ninja. You've died!

Ha ha! laughs Graceful.  That was a very good riddle. Who's next?

Doesn't anyone want to know the answer? asks Wittgenstein.

I do, says Gaius. Is it seventy five?

No, it's sixty seven and a half says Wittgenstein. You see the female-female possibility has been eliminated, leaving male-female, female-male or male-male. Two thirds chance of you licking a female. Of course it goes without saying you must lick both frogs.

Fascinating, says Gaius.  Well done, second ninja. A mind-stretching riddle.

I got it right straight away, says Terence.

You did, actually, says Graceful. But you didn't explain your workings.

I didn't do any workings, says Terence.