Sylwain, as you would know, snakes don't need to eat a lot. Especially around times of low activity. One mistake made by people is to overfeed their snakes and keep them in a container where they can't, or don't need to, move around a lot. They then suffer from the same ailment that is plaguing the western world today - morbid obesity. Out around the garden they need to keep moving between food source, water and where they sleep over. Keeps them fit and healthy looking. Now I keep moving between food source, water and where I sleep over. But as a mammal I should probably be doing a lot more.
