Im assuming when you mean "adult" you mean fully grown adult, right? In which case feeding a rat pup would be pretty darn stupid lol. In some cases, an adult bp can be really undersized due to not being fed at the beginning of its life. My three year old female bp is little over 31 inches, she looks healthy but is just extremely small. She was fed rat pups all her life until I took her in. She's moved up to small rats right now, but I seriously doubt she's going to get that much bigger. And yea back to your point, ignorant pet owners