Although adverse environmental conditions such as cold temperatures, very hot temperatures, drought, poor prey abundance, and flooding may force some species of wild snakes to fast for several months, these conditions usually are not the case for captive animals. In addition, wild snakes usually do not enter a fast suddenly; there is usually a gradual period of cooling or reduction in prey numbers that precedes the fast. During this period, the snake's body has time to adapt to the fasting state.

When enduring a forced fast, snakes reduce their activity levels and the basic rate at which their body burns calories. They slow down their metabolism until the environment is favorable to them successfully hunting again. Herpetologists that hibernate their snakes have recognized the need for slow transitions for years. If snakes are not given the time to pass the feces of their last meal prior to a serious drop in temperature, the food left in the gut will rot and make the snake sick. In general, except for hibernation, snakes in captivity are not given the environmental cues necessary for them to successfully fast for long periods of time.

If you have acquired a snake that is not eating and someone tells you that this is normal, be careful. Unless the snake is purposefully being manipulated by cooling or change in water availability or just getting ready to shed, the anorexia is probably abnormal.

Neonatal snakes do not usually feed until after their first shed approximately two weeks after hatching. Until this time, they live off of the remnants of their yolk sac.

Causes

Although many cases of anorexia are secondary to poor husbandry, the following is a list of common medical problems that are associated with anorexia in snakes:

Mouth infection (infectious stomatitis, mouth rot)

Pneumonia

Intestinal parasite infection

Kidney disease

Liver disease

Inclusion body disease of boids

Systemic or intestinal bacteria infection

Retained eggs

Intestinal impaction

It is important to determine that a snake is really anorexic. Many snakes are overfed in captivity and simply cannot eat as frequently as their owner wishes to feed them. An excellent diet history and a normal physical examination with the exception of obesity is usually diagnostic for this condition. A conclusive diagnosis is made when the snake's appetite returns after a decrease in portion size and an increase in feeding intervals is instituted.