We keep records for all of our snakes, each snake has an individual chart with columns titled: Date, Feeding, Weight(as we occasionly weigh them), vivarium( for any changes we make to the tank) and Comments, which is just for additional notes. I find it very useful for keeping track of how often a snake feeds, and its good for spotting any signs of problems or changes in behavior due to illness or changes in the tanks.

And if an animal needs treatment at the vets, we start a medical record so we can keep track of treatments and monitor its recovery.

We've filled a ringbinder with all the records.