Rats hyperactivity in cycles

Question
I have found no information on this on the Internet and wondered if you can shed some light on this. My pair of female rats at around 16 months of age started having bouts of hyperactivity in cycles of around one week on and one week of normal behaviour. When they are hyper, they act like they have attention deficit disorder, they aggressively groom their cagemate, they drag them back to their box by the scruff of the neck, making them squeak in protest, they obsess about filling their box with stuff, they chew their box and bed till it is in shreds, they run around nonstop, and generally have huge amounts of energy for hours at a time. It is exhausting to take care of them when they are like this because they are not hyper at the same time and I try to protect the one from the other when it gets really bad and the non-hyper one needs a break from the hyper one. They are now 19 months of age and one of them is hyper less and less with just small bursts of hyperactivity for a couple days, but the other one can go on for several days at full force with no let-up in sight.Then they are back to their normal selves again for a week or so, just being normally playful, like they were for the first 16 months of their lives. I have read about the dragging being a maternal behaviour, but the hyperactivity in cycles is something that my vet said must be hormonal, but I still have not heard of anyone with this same problem. Are my rats the only rats who do this? How normal can this be if no one brings it up in any forums? Thanks for any information you may have.

Answer
Hi Paola,
I'm sorry I didn't answer sooner. I meant to, but then forgot.  I have never heard of rats doing this before. It is not normal rat behavior. Maybe there something in their environment that changes that you haven't really noticed. For instance, how often to you do laundry? Is your home sprayed for bugs regularly? Do you give them different foods from time to time?
Deb