I'll try it ... Let me. You make pages?
Magento create page (user's views) with categories. So In Calalog-> Manage Catgories ... You must create two main categories "Dog Food" and "Cat Food". Inside it one of them you must create subs. (1)
Now. You have to categorize each product in your specific category and magnto make the links. Remember. You must be sure this option in general tab in each category "Include in Navigation Menu * = YES"
Categories, Pages and Static Block are different things for magento but in sometimes they are the same thing for the user.
I hope I can be able to help. This is my first attempt to help someone here.