Copyright is an interesting thing. Mainly in how it can nest, and the restrictions that can result from that.
Nesting
Take a look at this photo.
You might look at the corner and think that I own the copyright, and that I can do whatever I want. But that not entirely the case. While I own the copyright on the image, the lion is owned by someone else.
Now, if that were a wild lion, I could do whatever I wanted. But it isn’t1, this lion is owned by the Maryland Zoo.
Pretty much every zoo lets you take pictures, it wouldn’t be a decent zoo if they didn’t. However, they tend to only allow photos for “personal and non commercial” use. The main side effect of this, is that that I can’t offer a print of this photo. Or really any, that I’ve taken at the zoo.
Now a lot of people will argue about the validity of those restrictions. But the easiest thing to do, is just respect them. Most zoos have a process anyway to be able to take commercial photos. Something I might start looking into2.
Even without going through all that, zoos are still a great place to practice and learn3. Sure I can’t offer prints of what I take, but practice makes perfect.