The study of animal behaviour is called:

Many scientific disciplines are named by joining a Greek or Latin root with the suffix "-logy," meaning "the study of." Reading the root tells you exactly what a field studies — for example, "bio-" (life), "eco-" (habitat), or "ethos" (habit or character).

The question asks which field studies the behaviour of animals. That field is Ethology — the branch of zoology devoted to the scientific study of how animals behave, especially their natural, instinctive behaviour patterns.

• Etiology studies the causes or origins of a disease or condition — its root is the Greek "aitia" (cause), unrelated to behaviour.

• Neology deals with the coining or study of new words and terminology, a linguistic field, not a biological one.

• Demology studies human populations and their social or demographic characteristics, not the behaviour of animals.

Cross-checking the roots confirms this: "ethos" (habit or character) is the base of Ethology, so of the four terms only Ethology directly names the study of behaviour — matching the stem exactly.