The second largest rodent in North America porcupines are unusual in that they are covered in quills with an adult having around 30,000 sharp barbed quills. The quills are a secondary defense – first is fleeing up a tree! Porcupines love salt and chew on whatever they find that has it – plywood, shoes and pretty much anything with salt or sweat residue. If you have porcupines in your area you can place a salt lick near where they like to chew and this can save your shoes and keep everyone satisfied.