Seeing and not seeing.

Recent studies revealed that although subterranean mammals inhabit a dark underground environment, they can still perceive light stimuli and use this to entrain their circadian activity rhythm. Regarding spatial orientation, olfactory and tactile cues are employed for short-distance; whereas for long-distance, subterranean mammals employ the earth's magnetic field and self-generated (vestibular and kinestatic) cues. We suggest that seismic signals, utilized for long-distance communication, might also be used as an echolocation mechanism to determine digging depth and presence of obstacles ahead. Taken together, these mechanisms provide an equally efficient means of overall orientation and communication as those found in sighted mammals.