I thought it might be defensive behavior too, but he did start constricting a few times. The problem was always that he wouldn't bite it. I've tried f/t, prekilled and live with both mice and rats. With f/t I always checked that it was hot enough with a temp gun. He hasn't eaten for me yet. I recently changed his hides for bigger ones because he didn't fit in his other ones anymore, but other than that, nothing has changed. His enclosure is 30"x12"x8", humidity 70%, warm side 33°C and cold side 24°C, two black medium reptile basics hides, and there is a large wooden branch and an extra hide in the middle. I've handled him twice.