First of all, they're called QUILLS! And it's to protect themselves.
no it does not use spikes to protect itself
Porcupines are rodents with spines (or quills as the are also known).
its a protection which animal have to protect itself from the predator...
to protect itself from creatures that could harm it.
Quills
i think so; otherwise the quills would not hold on
Yes, hedgehog quills are modified hairs.
Spines IS the correct term when referring to the echidna. The questioner is probably looking for the answer "quills", but this word is usually used in reference to the porcupine. Echidnas and porcupines are not related at all. Therefore, echidnas have spines and porcupines have quills.
So that the sea urchin can protect itself from is enemies, it also has venomous spines. They also use their spines to kill other sea ceatures, so they can eat them.
Hedgehog's spines are called quills. They are used for self-defense. Hedgehogs roll up into a ball and stick their quills out. They huff and jump, which pokes the quills into the attacker.
The 'spines' of a cactus attach directly to the stem of the plant.