The only problem with the gerbils is that it can be very difficult to get them eating mice or rats again after they've discovered gerbil is an option if they hold out for it. I would only try that as a last resort and only if I knew for certain he was losing significant body weight or hadn't eaten in at least 3 months. Otherwise you'll find yourself paying as much as $8 or $9 every week for food for one snake or breeding an animal you hadn't intended to even keep.