The most immediate application of behavioral knowledge in veterinary medicine is in the diagnostic process. An animal cannot describe its symptoms, but its behavior provides a continuous, eloquent narrative of its internal state. A cat that suddenly begins urinating outside its litter box is not being "spiteful"; it may be exhibiting a classic sign of feline lower urinary tract disease or painful idiopathic cystitis. A dog that becomes aggressive when its back is touched is not "dominant"; it is likely communicating profound pain from a herniated disc or arthritic hips. Without a behavioral lens, a veterinarian might treat the symptom (inappropriate elimination) or sedate the aggression, missing the underlying pathology. By understanding behavior as a clinical sign—a form of non-verbal communication—veterinarians can use ethograms (behavioral repertoires) to localize pain, assess neurological function, and differentiate between primary medical diseases and primary behavioral disorders like anxiety or compulsive disorders.