Corn snakes in the wild will eat a variety of different foods, including lizards, birds, and small rodents.  Anoles and other lizards provide the main food source, and as such, baby corn snakes often prefer lizards over mice.  Because of the ready supply of mice available and the low cost, they are the preferred food item for corn snakes.   The size of mouse to feed the snake depends on the size of the snake.  New hatchlings will normally eat the smallest size pinkie mouse available.  As the corn snake grows, the size of the food item can be increased proportionally.  Generally we feed a mouse that is approximately the same or slightly larger diameter than the diameter of the snake at  it’s largest girth.   Feeding too small a mouse may restrict the growth rate of the snake; while feeding too large a mouse may cause the snake to regurgitate the meal.
   Most owners feed corn snakes frozen thawed mice.  These can be purchased at many pet stores or they can be ordered in bulk from various internet providers.  The advantage of the bulk order is in the price of the individual mice can be much cheaper then at a local pet shop.  Live mice may seem an attractive alternative to frozen thawed, but there are some precautions that should be heeded.  Corn snakes are creatures of habit, and once they become used to live mice, they may not eat frozen thawed ones.  This could pose a significant problem if the source of live mice disappears.  A more serious concern is feeding adult mice to larger snakes since they can attack the snake if left in the cage with it.  For this reason, we always either pre-kill a live mouse or, preferably, we feed frozen thawed mice. Frozen mice must be thawed completely before feeding them to the snake.  A partially frozen mouse can cause harm or regurgitation when it is swallowed.  Mice can be thawed by soaking in warm water for several minutes; the larger the mouse, the longer it will take.  Once thawed, mice should not be re-frozen again, and uneaten ones should be discarded.
   As in behavior, feeding tendencies are vary for different snakes.   Some will readily eat whenever food is offered; while others will only eat on their own schedule.  Most of our corn snakes will readily eat an appropriate size food item twice per week.  Some, however, prefer to eat only once per week.  Many corn snakes will not eat during the shedding process.  This may last up to a week.  For this reason, it is good to keep track of the feeding and shedding schedule in order to explain the refusal to eat.  Usually the snake will eat again right after they finish shedding.
It is a natural reaction for corn snakes to constrict the prey, and they will readily do this with live mice.  With frozen mice, the snake does not have to constrict the mouse  during feeding.

1. Due to feeding while shedding
2. Feeding oversized mice
3. Eating spoiled mice
4. Due to low temperatures in the cage (less than 70 degrees F)
5. Due to illness

Since illness can first be noticed by regurgitation, it is important to determine the reason if the snake regurges.   If illness is suspected, the snake should be taken to a qualified herp veterinarian for diagnosis and treatment.  After a regurgitation, the snake should not be fed again for at least 7 days to allow the gastrointestinal fluids to build back up.  The next feeding after a regurge should be a smaller food item.  For hatchlings, if they regurgitate, it is recommended that the next feeding just be the head of a pinkie mouse.
Obesity in adult snakes is common, and is unhealthy.  When a corn snake reaches the adult size of 36 inches, the feeding schedule should be reduced to not more than once per week.  For adult males the feeding may be every 10days.  Females who are being bred may be fed twice per week before breeding and after the post egg laying shed. Some people raising corn snakes power feed the hatchlings to get them to reach adulthood in less time.  Feeding on a normal once per week basis will generally develop a snake from hatchling to adult in about three years.  Power feeding, which is feeding the snake at least twice per week or  the maximum amount it will eat, can result in a snake developing to adulthood in less time, often one to two years.   Power feeding should be slowed when the snake reaches 36 inches in length to prevent obesity.