Given this paragraph about hedgehogs, why are they different from porcupines?

Hedgehogs are easily recognized by their spines, which are hollow hairs made stiff with keratin.Their spines are not poisonous or barbed and, unlike the quills of a porcupine, do not easily detach from their bodies. However, the immature animal's spines normally fall out as they are replaced with adult spines. This is called "quilling". Spines can also shed when the animal is diseased or under extreme stress. Hedgehogs are usually brown, with pale tips to the spines, though blonde hedgehogs are found on the Channel Island of Alderney.

Hedgehog spines do not easily detach rom their bodies like porcupines.