This is what behaviorists call "the stress mask." Prey species (dogs, cats, rabbits, horses) are biologically wired to hide pain and weakness. In the wild, showing vulnerability gets you eaten. Therefore, by the time a physical symptom is obvious, the disease is often advanced.

The MSD Veterinary Manual notes that modern welfare standards, such as the "Five Freedoms," emphasize the importance of allowing animals to express natural behaviors while remaining free from fear and distress. Innovations in Training and Diagnostics

The Essential Guide to Understanding Animal Behavior for Vet Assistants

Animal behavior and veterinary science are two closely related fields that aim to understand and improve the welfare of animals. Animal behavior is the study of the actions and reactions of animals in response to their environment, while veterinary science is the application of medical science to the health and well-being of animals. The intersection of these two fields is crucial in understanding and addressing behavioral problems in animals, which can have significant impacts on their welfare, human-animal interactions, and even human health.