You gain the scent special quality, including the ability to track by scent. You receive a +8 competence bonus on Perception checks involving smell and a +4 competence bonus on Survival checks to track using scent. You take a -4 penalty on saving throws against odor-related effects such as the stench ability and stinking cloud. A creature under the effects of bloodhound can detect poison by scent with a DC 20 Perception check.