Ferrets are curious creatures that need a variety of toys and activities. Our ferret loves to dig, and one of his favorite activities is digging in a plastic tub filled with rice. We make sure it is not available at all times so that it remains a special treat. As much as he loves the rice, if given a choice, he would choose to dig in the dirt of my ficus or citrus tree. He also loves to "tunnel" under the covers of our bed. He is not normally a biter, but for some reason, he will bite any toes under sheets. My theory is that since ferrets are tunnelers and are carnivorous, then he must have some instinct to eat what he finds while tunneling. Maybe the toes are "earthworms" to him. When my kids were small, they also loved to play in their rice box. Their rice was multi-colored though. We have added a few PVC pipes (we smoothed all rough edges with sandpaper). Occasionally, we add some cardboard mailing tubes as well.
Ferreting out the Law