Light perception in ‘blind’ subterranean Zambian mole-rats

Because of their constantly dark habitat and microphthalmia, subterranean African mole-rats have hitherto been considered as blind. Recent morphological findings, however, revealed a qualitatively rather well-developed, although quantitatively reduced, visual system and questioned the prevailing idea of blindness. We investigated the reactions of Zambian mole-rats of the bathyergid genus Fukomys (formerly Cryptomys) to white light during nest building. Using a two-armed test chamber with a choice between strong halogen light and darkness, we found that mole-rat pairs avoided the illuminated chamber and nested significantly more often in the dark box. With the same protocol in an eight-armed maze, we confirmed this heliophobic (or scotophilic) behaviour under natural daylight conditions. Zambian mole-rats can thus perceive natural light intensities and use photic information, for example to decide where to nest.