[Stefan-A]

Thanks, KitKat. Very useful.

However, I don't necessarily agree with your conclusion. Many garter species do include them, or rather, they don't exclude them from their diets. Second, their current situation doesn't give any kind of information regarding the direction of their evolution. Is eating mice becoming more common, or less common? Their strength has been the ability to change food source depending on competition and availability. The specialized rodent eaters don't really have that ability, even if they can take birds. Amphibians are the most common prey, and logic says that one should try to feed them animals that are as close as possible to them in terms of nutritional content. Whichever comes closest, mice or fish, doesn't matter. The point is that worms are very different.

The calcium content is a concern though, even if it appears to me to be easier to supplement than I thought at first. The availability is however a bigger problem. But most of all, it's probably the issue of having a snake change its preferences so drastically, that's unnerving.