How much does one of these rats weigh? A medium size rat that I buy from my suppliers would be an absolutely massive meal for all but the very largest BPs. My adult male (1.5kg) can sink a small rat but I ultimately found him to feed more consistently on the smaller 'weaner' rats. This size rat seems to be labelled as 'small' in some pet shops. The rule of thumb should be a prey item about as large around as your BPs biggest girth.