User blog comment:GSFB/Vampires vs Berserkers/@comment-5365454-20120925233329/@comment-5232784-20120925234940

Ulfhednar were originally differentiated from the Berserkers, due to wearing wolfskins instead of bearskins, no shields, having their own skin painted black before battle, howling on Viking ships before fighting, etc. Later they were absorbed into the name Berserker, but they were still different. They were so wolf like in behavior and activity that, while Berserkers were considered men acting like bears, Ulfhednar were believed to be wolves while in their feral battle mode.

Ulfhednars were a major source of later European werewolf tales.