Of all of the features of your pet hedgehog, probably none stands out more than than the quills. When you really stop to think about it, they really are quite remarkable. They are the main means of defense that a hedgehog has against predators, but they serve some other rather useful purposes as well.
Although scientifically described as being modified hairs, each of the roughly 7000 quills on a hedgehog’s back is far more complex than any hair possibly could be. Rather than being solid inside, each is filled throughout with complex network of air chambers. Not only does this make them very lightweight and strong, but it also helps to prevent buckling and breakage.
At the base, the quill narrows to a thin stem where it enters the skin and is firmly anchored in the muscle tissue by a small, ball-shaped follicle. At the opposite end, the quill narrows to a needle-like point and is bent slightly back to provide maximum defense should a predator be interested in having hedgehog for lunch! When attacked, it is the contraction of the two large muscles that run down either side of the hedgehogs body that cause the quills to be raised in defense. When those two muscles are contracted, (much like pulling the draw strings on a purse) they pull against the ball-like base of the quill, drawing it into an upright position. Since the muscles pull different quills in different directions, they tend to crisscross one another, forming a near impenetrable barrier.
They are, however, not only there for defensive purposes. Hedgehogs are noted for being skilled climbers but, like cats, are not very good at getting themselves back down again! When they do come across a drop that they cannot climb down, they will simply roll into a ball and drop, allowing the spines to cushion the fall. To prevent the quills from being damaged or lost, the thin stem just above the skin flexes upon impact. Although we do not recommend you try this at home, wild hedgehogs have been seen dropping from heights of up to 20 feet with no apparent signs of injury! hedgehogcentral.com