Monitoring of changes in appetite is considered a basic tool for the veterinarian taking care of cetaceans. Fluctuations in appetite, while a potential sign of illness may also be explained by other factors which may include 1) species and individual differences in food acceptance, 2) food quality, 3) food preference, 4) satiation from over feeding, 5) hormonal influences in cycling females, and maturing and mature males, 6) social incompatibility, and 7) environmental instability. Differentiation from illness factors may be accomplished by observation, knowledge of potential differentials, blood work, periodic weighing, nutritional analysis of food items, and response to diet manipulation. Documentation of many behavioral etiologies may be dependent on long-term detailed histories coupled with pre and post incident observation. Hormonal influence on diet may be aided by the monitoring of reproductive hormones in females experiencing seasonal intermittent behavioral and dietary anomalies. Males may experience short to prolonged periods of decreased appetite which may be associated with increased testosterone levels in adults and non-fertile breeding behavior in juveniles.