- 2010 Elsevier Ltd All rights reserved. Animal behavior reflects animal health. In turn, health can be reflected in changes in behavior associated with illness as well as strategies used to prevent disease. In addition, a number of abnormal behaviors may be the only indicators of health problems. In other instances, medical cases present as if they were a primary behavioral problem. The brain, endocrine system, and behavior are so interrelated that little changes in one can have significant consequences on the other.