Why do burrowing shrews have tiny eyes and ears hidden by fur?

Burrowing shrews, such as the North American short-tailed shrews, have evolved minute eyes and small ears hidden by their fur as an adaptation to their specialized lifestyle. Because these animals construct and forage within subsurface burrows, spending only limited time on the surface, they do not rely on vision or external ear structures to navigate their subterranean environment. These anatomical modifications protect these sensitive organs from debris and injury while the shrews move through their tunnels.1