The tree porcupine is heavy, growing to be 10-20 lbs or even bigger depending on diet. Their entire body is covered with quills which can number over 20,000. Only the face, under body and under the tail don't have any. Although the quills can dislodge easily, porcupines cannot "throw" quills at will. They generally take a defensive stand daring predators to bite knowing their quills will protect them. In some cases, they may lunge, but porcupines are not swift nor do they pretend to be. If you get too close, they may slap their tail, but in general will leave you alone unless antagonized.