The feeding sizes, I have been told, is up to approx 3 times the diameter of the snake. I have found this advice useful. Rodent sizes tend to vary depending I where you buy them.
The only thing I would add is that, if you feed them the larger sizes, or if they haven't eaten for a while, my fellows will "kill it" and then rest and wait for a while before starting to eat. I think this because they are waiting for their stomach to enlarge. It seems that a snakes stomach shrinks when not eating and gets bigger before they eat.
Hi Sherlock,
You're on the money when you say that a snakes stomach will increase in size to accommodate the food item.
Basically, what happens with sit and wait ambush feeders like pythons who eat periodically is that following digestion of a meal (which dependent on the size of the meal can take between 7 days and a few weeks) the snakes metabolic activity decreases to a bare minimum which includes a reduction in the size of the digestive system..
Then once the snake has captured and secured a new food item their metabolic activity increases 2 or 3 times, (dependent on the size of the food item) whereby the size of their heart increases as a means to pump more blood through their body to boost their digestive system. During this time their heart, lungs, stomach, lining of the intestines, kidneys and liver can increase in size as much as three fold. Around the same time the ph of the stomach acid drops to allow the gastric juices to work on digesting the meal. As the gastric juices work on the meal the stomach muscles churn the food to further assist digestion. Then as the meal liquefies and enters the intestines it is broken down further and the newly thickened lining of the intestines absorbs the nutrients and disperse them throughout the snakes body.
During the digestive process the snake's oxygen level also increases to assist with the digestive process and they can use as much as half the energy they get from the food item to help digest the meal as well.
The whole process can place a great deal of stress on the metabolism of the snake and again dependent on the size of the meal it can take between several days and a number of weeks for a snake's metabolic activity and organs to return to normal once the item has been fully digested. The snake will also seek out a heat sourse to assist digestion as well as offset the strain placed on its metabolism during the process.
If a meal is too large or the snake is disturbed during eating then it will simply regurgitate the meal. However if, for what ever reason, the meal starts to rot in the snakes stomach it will vomit the meal up. Neither process is good for the snake's digestive system.
And, because of the stress placed on a snake's metabolism during the digestive process it is advisable to allow a snake a period of rest following digestion for it's metabolism to recover before offering the next feed. Again this is dependent on the size of the meal.
George.