Quilboar keep to themselves. Although they hold a strong hatred for other races, they are not openly aggressive toward them. They are, however, extremely possessive of what is their's, and with the Horde's encroachment on their lands, they have begun to retaliate. A common theme in Horde quests in Durotar, Mulgore and The Barrens is dealing with the "aggression" of the quilboar.
There are several different tribes of quilboar, including the Palemane of Mulgore, the Razormane and Bristleback in The Barrens, and the Razorfen and Death's Head tribes which live in Razorfen Kraul and Razorfen Downs, respectively. Notably, the Death's Head are working with the Scourge. The opposing tribes are led by Charlga Razorflank, aka the "old crone."