What do leeches eat in the wild?

Most leeches will eat an entire earthworm whole!

But they ALL have a passion for blood.

I'm not recommending it, but you can take your pet leech and let him leech of you, your dog/cat/hamster/whatever for about 20 minutes until he/she gets full. They only consume a few cc's of blood, but you have to be careful as they may be carrying diseases...