It's important for owners to be aware that even seemingly insignificant, short-term changes in a pet's normal behaviors, such as play and eating habits, can be subtle indicators of a serious underlying problem, writes veterinarian Christie Long. Fever, pain, anemia and toxin ingestion are just some of the potential causes of an animal's behavior changes and early evaluation by a veterinarian is essential for the pet's health.  The Coloradoan (Fort Collins, Colo.)