What does mastology, also known as theriology, study?

In zoology, mammalogy is the study of mammals – a class of vertebrates with characteristics such as homeothermic metabolism, fur, four-chambered hearts, and complex nervous systems.

Mammalogy has also been known as "mastology," "theriology," and "therology." The archive of the number of mammals on Earth is constantly growing, but is currently set at 6,495 different mammal species including recently extinct.

There are 5,416 living mammals identified on earth and roughly 1,251 have been newly discovered since 2006. The major branches of mammalogy include natural history, taxonomy and systematics, anatomy and physiology, ethology, ecology, and management and control.

The first people recorded to have researched mammals were the ancient Greeks with records on mammals that were not even native to Greece and others that were. Aristotle was one of the first to recognize whales and dolphins as mammals since up until the 18th century most of the study was done by taxonomy.