Historically, the leading cause of death for young, large-breed dogs was not disease—it was behavioral euthanasia for aggression. While serious behavioral pathologies exist, many of these cases were rooted in undiagnosed medical pain (e.g., hip dysplasia, dental disease, hypothyroidism) that manifested as irritability. Without bridging behavior and medicine, healthy dogs were put down for being "mean," when they were simply hurting.

. While veterinary science traditionally focused on physiology and pathology, modern practice increasingly relies on applied ethology

Animals cannot speak. Therefore, their behavior serves as their primary language. For a skilled veterinarian, a change in a patient's routine or posture is just as telling as a blood test or an X-ray. Recognizing Pain and Illness

Avoiding direct eye contact, towering over the animal, or making sudden movements.