Quills or spines? All quills are a form of spine. Confusing, I know. A spine is a word for any hard, pointed, appendage on an animal. For example sea urchins, lizards, fish and hedgehogs can all have spines. The word "quill" is more specific. It describes the type of spine that you are referring to. For example, a porcupine quill.
I've acquired some quills of the North American porcupine, African porcupine and the African pygmy hedgehog and wanted to share some differences between the three.
From left to right: African pygmy hedgehog quills, North American porcupine quills, African porcupine quills
All Quills are modified hairs that are made from keratin, the same thing that our fingernails are made from! Hedgehogs have very durable quills that are difficult to break. The quills are all relatively the same length, under 1". Their quills are not easily released, instead they are anchored into the skin with a bulbous follicle. When threatened the hedgehog uses its quills by completely balling up to protect their soft underbelly. Hedgehogs are also quite resilient to falls, thanks to their quills!
North American porcupine
Contrary to popular belief, porcupine quills are not poisonous and porcupines cannot shoot their quills. American porcupine quills are 1-3" in length, loosely rooted, easily released and tipped with barbs that get stuck into the skin of their predators. Each individual quill has up to 800 backward facing barbs that act like hooks. The quills are extremely sharp and pierce through skin with only the smallest amount of force. The barbs make it incredibly difficult for the quills to be removed. American porcupine quills lie flat along the back. When threatened, the porcupine will raise its quills to protect themselves from the attacker.
Barbs on the tip of an American porcupine quill
African porcupines are much larger than American porcupines. They have quills of various lengths, ranging from 1-13" long. The quills are hollow and can break without much force. Their quills are also loosely rooted and easily released, but unlike American porcupines, their quills are smooth and unbarbed. When threatened by a predator, the African porcupine will run backwards and ram the attacker with the short, thick spines on its rear.
African porcupine quills