A good candidate for this type of sensor are the mystacial vibrissae in small-sized mammals. Visual input appears to play a minor role, at least in albino strains of labo-ratory rats, which are largely deprived of this sense due to structural abnormalities in the visual system related to albinism (Abadi et al.,1990; Prusky et al., 2002). But wild rats and pigmented domes-ticated rats also use their visual sense rather as light detector or to avoid larger obstacles in their path because contrast sensitivity is quite low compared to mammals with a distinct dominance of vision (Birch and Jacobs, 1979).