Can you earn a Doctorate in Zoology, and what can you do with it?

I've always wanted to work with animals. I've worked at a couple zoos now getting to talk to keepers and did one animal care internship. So I know alot about what I need and can do up to a Bachelors degree. But can you get a doctorate in Zoology, or would it be in Biology with just an emphasis on Zoology? And what can you do aside from teach with one such degree? Do you need to have a Doctorate for these jobs or does it just make you more valuable? Any specific info is great, thanks.