Zoology is the scientific study of the characteristics and classification of animals. It is one of the branches of biology, and therefore it is also referred to as animal biology. There are several sub-branches within this field, including ethology, zoography, and anthrozoology. Additionally, zoologists often specialize in the study of specific types of animals. For instance, an ornithologist studies birds, while a mammologist studies mammals. As zoology is a very interdisciplinary subject, there are a number of related fields, including taxonomy, paleontology, and evolutionary biology.