Animals are a favorite photographic subject while traveling. I love watching their routines and interactions with locals. They add soul to landscape and urban scenes. Unlike people, they never mind having their pictures taken. Sometimes they'll even talk to you:
My favorite photography book is Cats of the Greek Aisles. The huge diversity of healthy Aegean feline specimens juxtapose the organic curves of their gorgeous island home perfectly, resulting in the most beautiful compositions I've ever seen. A must-read!