This document discusses animal behavior and ethology. It defines behavior and describes the three main approaches to studying behavior: vitalistic, mechanistic, and ethological. The ethological approach attempts to explain responses observed in the field in terms of eliciting stimuli. Behavior can be species-characteristic innate behaviors or individual learned behaviors. Stimuli that influence behavior can be internal or external. Motivation precedes behaviors and is influenced by physiological and environmental factors. Communication and sign stimuli also impact animal behaviors.