Your corn snake should be fed captive-bred rodents only.
Lizards, birds, and rodents (wild or captive-produced) can transfer parasites to your snake, so only feed such items after deep freezing.
Freezing does not necessarily render a food item harmless to your snake. If you feed any such item to your snake that has been in contact with toxins, they will be transmitted to your snake, regardless of freezing. Likewise, some diseases and pathogens are not killed by residential freezing.
If your snake refuses domestic rodents, consult a professional snake breeder or corn snake book for temporary alternative recommendations.
Regarding what size prey to feed your corn snake, a general rule of thumb is to feed a rodent that is under twice the diameter of the snake’s mid-body girth (preferably 1.5 times the snake’s girth), but only if proper digesting temperatures are continually available to your pet.
The first meal you feed your snake upon receiving it from someone else should be 25% to 50% smaller than normally consumed by a snake of that size. This is because the stress of transportation and the snake’s new surroundings could cause your new snake to regurgitate. Also, until you are certain the new cage has stable temperature zones per CAGING recommendations in this care guide, feeding your snake a meal it is not capable of digesting may result in regurgitation. Any time a corn snake regurgitates, it is an event of great concern. Contact a qualified reptile veterinarian or a professional corn snake breeder before offering another meal. Strict post-regurgitation therapies should be followed after any regurgitation, but the most important is that you do not feed an appropriately sized whole rodent to a snake that has recently regurgitated/vomited. Feed much smaller rodents (or parts thereof) after waiting 7-10 days to feed a post-regurgitation meal. Since it takes so much longer for snakes to replenish lost stomach acids from a regurgitation–compared to mammals–feeding too soon or too much after a regurgitation can ultimately lead to the death of an ill snake.
Hatchling corns (one to 15 or 20 weeks of age) will eat one-day old mouse pinkies (newborn mice) once or twice weekly. They will often want more, but feeding more than this can be dangerous to the health of your snake unless you have optimal temperature zones in the cage. A rule of thumb regarding the size you feed is that if the bulge corresponding to the food item in the stomach of the snake is not obvious 24 hours after feeding, you should be able to graduate to the next prey size.
The normal progression of mouse sizes in the hobby is: small pinky – large pinky – fuzzy – hopper – weaned (small adult) – adult.
Pinky number 1 in the pic above represents a typical 1-day-old pinky.
The Picture on right shows a typical 1-day-old pinky next to an Extra Small pinky.
1-day-old pinky mice
IMPORTANT NOTE: Not all suppliers of rodents in the industry have the same size definition of Extra Small pinkies, so understand what size they call EXTRA SMALL before you purchase.
We recommend acquiring your frozen rodents from one of the many Internet rodent businesses. Sometimes pet stores run out of some sizes of frozen rodents, so having an inventory in your freezer ensures that you will always feed the correct size to your snake.
In healthy snakes with proper cage temperatures, digestion is generally complete in three days. It is advisable to feed pre-killed or stunned rodents, as there is a slight possibility of injury from the prey during the kill. Of course, pinky mice have very soft claws and no teeth, so they pose no obvious injury threat to your snake.
If you DO feed live prey, be sure not to leave the snake unattended until after ingestion. If your snake refuses the rodent for any reason, remove it, and repeat the offering on another day.
If your snake unexpectedly refuses food, consult an experienced snake keeper or qualified reptile veterinarian for advice. Do not repeatedly offer what your snake is refusing to eat, as it may become conditioned to reject that prey item in the future, and you may be wasting valuable time in correcting potential health problems.
The most common cause of food rejection in corns is improper cage temperature zones. Corn snakes can fast for long periods, but only if necessary, so establishment of a routine feeding schedule is recommended. It is not necessary to strictly adhere to such feeding regimens, but long periods of fasting are not recommended unless you are (brumating) your snake in preparation for breeding – and then only under proper temperature conditions.