My young ratsnake does this too. She's never constricted. As a baby she would simply go up to it and eat it. Then as she got a bit older she would drag it to her hide. Now she will quickly grab it as soon as she recognizes its prey, and then let go and eat it. I think, as ferociously as she is starting to grab it, she would constrict a live one no problems, but lucky for her she doesn't have to. :-)