Her initial findings suggested that the chimps were suffering from a gastrointestinal infection, possibly caused by a parasite or bacteria. However, as she dug deeper, she discovered that the problem was more complex. The infected chimps had all been exposed to a new, contaminated water source that had recently become available in the forest.

Today, those lines have not only blurred; they have merged. The modern understanding of reveals a symbiotic relationship: behavior influences health, and health influences behavior. Ignoring one makes the treatment of the other nearly impossible.

For a veterinarian, behavior is a vital sign.

A major application of behavioral science is within the clinic itself. Historically, veterinary visits were often traumatic for animals—restrained forcibly for exams or vaccinations. This created a cycle of "white coat syndrome," where the animal’s fear made them dangerous to handle and difficult to treat.

This study evaluates the efficacy of environmental enrichment in reducing stress for cats in a veterinary hospital setting. Behavioral data and physiological markers (urinary cortisol) were collected from 40 cats divided into a control group (standard housing) and an enrichment group (provided with hiding boxes, pheromone diffusers, and elevated perching). Results indicate that enriched cats displayed significantly fewer "sickness behaviors" and lower cortisol-to-creatinine ratios.