What is the difference between hedgehog spines and porcupine spines?
Hedgehog spines are short, sharp spikes. The spines do not easily come out.
Porcupines spines are long, sharp spikes. They are called quills. The quills can easily drop out.
When a hedgehog is attacked, it rolls into a ball.

hedgehog spikes

European hedgehog (Erinaceus europaeus)
When a porcupine is attacked, it spreads its spines to form a shield.

porcupine spikes
Hedgehogs and porcupines are not related to each other.
Porcupines are rodents, like rats, mice, and squirrels.

Crested porcupine (Hystrix cristata)
Photographer: Martina Nicolls
Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM