Flickr

I just tried out Flickr for the first time. I uploaded and edited a picture of our new puppy. It was fun. After I did that, I explored the site a little and did a search for frogs. I found a lot of cool pictures that I might want to use for a project in the fall. Does anyone know if these pictures are copyrighted? I would think you need to ask the owner of the picture before you use it or print it, but I don't know enough about Flickr yet to know for sure.