What is a chronotype?
A chronotype is your natural tendency to be more active in the morning or the evening. Researchers have measured it since the 1970s with questionnaires such as the Horne-Östberg morningness-eveningness scale, and it is partly genetic and changes with age.
Sleep specialist Michael Breus popularized four animal types: lion (early riser), bear (follows the sun), wolf (night person) and dolphin (light, irregular sleeper). It's a simplified model, but useful for organizing your day.