there is a exellent artical in this months reptiles Magazine on Reptile Hydration a good read for any keeper. You might want to take a look at it, even though its not about Balls but Reptiles in general.

Just because you don't see your BP drink does'nt mean that he/sh does'nt. as stated above ball pyythons get most there food from there prey so its really importent to make sure that Feeders are Properly Hydrated themselves.

keeping humidity, fresh water and feeding properly hydrated prey through out the year is very importent to your BPs health!

The artical also mentioned that zoo med is going to start producing HUMIDISTATS this year, that can controll humidifires, waterfalls or fogers. Another way to make husbandy that much easier.

As for a clear sign of dehydration in ball pythons if they're Eye is dented, the BP is defenetly not properly hydrated, I had some trouble with naga over winter, Humidity was nothing but trouble, and she was off feed so I had to soak her at least once a week to make sure she was geting some H20.