Squirrels are easily recognized by their bushy tails. Squirrels are rodents, and their teeth never stop growing, so they have to chew to keep them filed down to a manageable level. Squirrels will chew through pretty much anything that isn’t made of metal and can therefore cause a lot of damage to homes.
Also, squirrels are very territorial. To defend their area, they will fight to the death. Mother squirrels are especially vicious when protecting their babies.