They are mainly nocturnal, and while foraging, continually sniff the air. They do not hibernate in the winter but will remain in the den during extreme cold or stormy weather. They are rarely known to attack but will defend themselves when attacked by climbing or fleeing. If cornered, they use the quilled tail for defense. Contrary to popular belief, they do not shoot these quills, but they back into the foe, causing the lightly-attached quills to detach themselves when entering the enemy's skin. They crave salt, and often gnaw at machinery, gloves, boots, saddles and bottles which have been touched by sweaty hands. Their predators are the wolverine, puma, and fisher-marten. Other carnivores will attack porcupines only as a last resort.