I'm not sure if this is the right category to post this but I recently read an article called “Dining With the Snakes” by Jared Diamond in DISCOVER Magazine Vol. 15. No. 04 from April 1994 Biology and Medicine. http://www.discover.com/issues/apr-94/features/diningwiththesna362/ I hope by referencing all of the above, I can freely call your attention to some interesting points made in this article without being in violation of copyright. I’ve paraphrased freely or quoted directly and used italics whenever I used a word-for-word passage. (The complete article was 6 pages long and included a lot of comparisons to human physiology... I'm just quoting the snake-relevant stuff.) I have a new-found respect for the physiology of my snakes after reading this article and now realize how hard the snake has to work to digest a meal… Some interesting facts found in the article: 1) a snake can open its jaws to an angle of 130 degrees 2) A snake’s jaw is hinged and the lower jaw is not fused together but connected by elastic ligaments. The skull and upper jaw also have parts that are flexible, so that the snake can stretch its head over and around its meal. (Snakes do not “dislocate” their jaws as they are not connected in the first place.) 3) Swallowing can take up to several hours if the prey is very large. Fortunately, the opening to the windpipe is located on the bottom jaw of a snake’s mouth and can be extended past the prey item, enabling the snake to breathe while swallowing. 4) Digestion is a race against time for snakes: they must digest before the animal rots inside its body releasing toxic chemicals that can cause regurgitation or death. 5) Digestion is aided greatly by warm temperatures. “That's one reason snakes will bask in the sun to warm themselves, or coil up to conserve heat--it speeds their digestive processes. An Indian python, fed a rabbit, completed digestion in four or five days when kept at 82 degrees, in a week when kept at 71 degrees, but still had rabbit in its stomach after two weeks when kept at 64 degrees. Indeed, if the temperature gets too cool, a snake will refuse to eat at all.” (Or if it has eaten and it’s too cool, it will regurgitate the meal… even weeks after it was swallowed!) 6) To examine the digestive process, these scientists X-rayed a snake at intervals after it was fed a rat. They found that the rat was dissolved headfirst: “two days after it is swallowed, its skull is gone, though the rest of its body is intact. By four days, the chest and front legs are dissolved and the hair has become detached from the skin. By six days, only an occasional vertebra or hind leg remains within the snake's stomach.” 7) To aid digestion and produce enough digestive acids to dissolve bones, a snake must increase its oxygen consumption. The article stated that they found an oxygen increase of 36-100 times depending on the size of the prey swallowed. 8) This part I just have to quote directly: “Another use for the energy became clear when we looked at the snake's intestine. When a python swallows a rat, its intestine doubles or triples in weight overnight. Each cell of the intestine's lining grows taller and wider and develops longer projections. All that extra surface area means that there's more intestine to make digestive enzymes--up to 60 times more enzymes--and to break down and absorb food. Synthesizing extra intestine accounted for a lot of the extra oxygen consumption that we saw in our fed snakes. When a rattlesnake swallows a mouse, its intestine grows quickly: to keep up, a 150-pound man would have to add 6 pounds to the weight of his own intestine overnight. In fact, the cost of making extra intestine and digestive acids is so high that the snake uses about a third of the energy it gets from a mouse's body just to digest the mouse's body! And a larger python, eating an even larger meal, can use up to half the energy derived from the meal. “ 9) And for those of you worried when your snake goes on a fast, the article had this to say. “In the wild, feeding intervals for rattlesnakes and big constrictors range from a few weeks to a few months. Pregnant female rattlesnakes will normally go one and a half years without eating; snakes in zoos have refused food for over two years. In other words, snakes swallow huge meals, digest them at leisure, and then wait a long time before eating again. Thus the snake's intestine has to be designed so that it can be called upon unpredictably, at short notice, to have a big load of digestive work dumped on it, and then do nothing for a long time until the dinner gong sounds again.” Of course any time your snake goes off its food, you should check your husbandry conditions: warmth, humidity, stress factors: as well as looking for any signs of illness. However, if all of that checks out… just give them some time and try again later! I thought I’d share this information for those of you who might just be curious, but also as a reminder to give your snakes plenty of time (and warmth!) to digest their food! They may look like they’re just “sleeping it off” but actually they are expending tremendous amounts of energy!