What are the different fields of animals you can specialize in?

I plan on being a zookeeper and was wondering what different fields or animal species I can specialize in. Like primates, etc. I would like to work with lemurs, koalas, giraffes, macaws, etc. What groups would those animals be placed in? Basically, I want to say "I specialize in working with _____" I just need to know what they are called. What would a giraffe be considered? Lemurs? Thanks!