The most obvious differences between hedgehogs and porcupines are size and defense mechanisms. A hedgehog is significantly smaller than a porcupine. It curls into a ball with spikes facing outward to ward off predators; the porcupine defends itself by stabbing attackers with quills.
The hedgehog is a small insect-eating mammal that grows 5 to 12 inches long and weighs up to 2 pounds. It is a native of Africa, Europe and Asia. Dense spikes cover its body, and it has short hair on its face, stomach and legs. When a hedgehog feels threatened, it rolls up. The pointed spikes frighten predators but remain attached to the skin.
The porcupine is a large herbivorous rodent between 1 and 3 feet long that weighs between 12 and 35 pounds. It lives in North and South America, Europe, Asia and Africa. Quills cover most of the animal's stocky body. These quills are modified hairs that can be solid or hollow, and either long and flexible or short and stiff. A porcupine's quills usually lie flat, but it raises them when threatened. It defends itself by stabbing its raised quills into the flesh of attackers. Although the quills can detach and regrow, the porcupine cannot shoot or throw quills at its enemy.