they have fragile spines. you can cause damage to the spine and not know it for a while. they can end up with spinal kinks that can be detrimental to reproduction if they are bad enough. this is why you should never by a GTP that has been popped or sexed to early. popping should never be done even on older animals and probing should be done when the animal reaches at least a year of age and over 100 grams.