Northern Leopard Frog

We have had northern leopard frogs hanging around our yard for the past couple summers.  Last year we had our backyard pond filled and they lived there.  This summer we had to empty it for the safety of our 1 year old son, but they are still around in the bottom of the pond where it fills with rain water and also in the longer grass near the gardens. The girls found one yesterday swimming in our kiddie pool. We caught him and made a home for him in a critter cage we purchased, used, a few weekends ago (just in case we found a critter of course!)  We had to go buy some crickets for him at the pet store until we can find a more sustainable way to feed him.  I figured out that it will cost us around $80 to buy crickets for him all year.  I am not going to do that.  I'd rather let him go, than spend that kind of money on a wild-caught pet.
We have to do some research about the types of insects he'll eat and how to catch them. Here's some pictures  of the last 2 summers.