The picture which emerges suggests that the star-nosed mole is an extreme in mammalian evolution, having perhaps the most sensitive mechano-sensory system to be found among mammals. There are two evolutionary theories concerning the star-like nose. One proposes the development of the structure of the star as a consequence of the selective pressure of the star-nosed mole's wetland habitat. Wetlands have a dense population of small insects, so exploiting this resource requires a higher resolution sensory surface than that of other moles. Thus, a shift to the wetland environment may have provided a selective advantage for a more elaborate sensory structure. Furthermore, in wild caught moles of many species, the Eimer’s organs show obvious signs of wear and abrasion. It appears that constant and repeated contact with the soil damages the sensory organs, which have a thin keratinized epidermis. Star-nosed moles are the only species which live in the moist, muddy soil of wetlands where the less abrasive environment has allowed the delicate star-shaped structure to evolve.