Tiny teeth are usually present on the tongue and the floor of the mouth behind the tongue. The lower sides are red during spawning season. In Montana, pure and moderately hybrid populations of westslope cutthroat have a high incidence of basibranchial teeth (teeth on the tongue and at the base or back of the tongue), whereas pure rainbow trout lack these teeth. It can be difficult to visually distinguish westslope from other cutthroat trout subspecies, but the westslope cutthroat trout tends to have more small spots by the tail and none by the pectoral fin and the fish is more of a silvery or greenish color. The only way to be certain about identification of this subspecies is by genetic testing.