Moles spend their lives underground, digging tunnels to reach their prey, which includes earthworms, grubs and any other insects they can find. In such a dark, dirt-filled environment, moles don't need senses such as powerful eyesight like some other animals do, but they depend on other adaptations for their health and survival.
Crawling around in underground tunnels all day would leave most creatures with eyes and ears full of dirt. Moles, however, have a thin layer of skin over their eyes for protection as well as eyelids shaped to help push dirt away, keeping their eyes clear. A mole's nostrils are shaped differently than most mammals. Instead of opening toward the front of the face, they open toward the side. This way, dirt falls around instead of into them. Also, moles don't have visible ears. Instead, they have small holes in their skull that are covered with a thin layer of skin to keep out dirt while still allowing the moles to hear.
A mole's front legs are short, stout, strong and end in powerful paws perfectly designed for digging. His legs don't bend the same way as most animals. Instead of bending toward his body at the elbow to support his weight while walking or running, they bend away from his body. This gives him the ability to quickly dig through tunnels in a swimming motion.
Since moles often have to travel both forward and backward through their tunnels, their fur has a special adaptation that lets it naturally lay in either direction. For example, dogs and horses have hair that lays in one direction, and if it is rubbed against the direction of growth, it lifts up, allowing dirt and debris underneath. A mole's fur has an unusual structure near the base that essentially allows it to swivel. When he is traveling forward in a tunnel, the fur lies flat toward his tail, but when he travels backward, it lies flat toward his head, keeping falling dirt off his skin.
Few mammals could survive extended periods in underground tunnels without a regular source of oxygen. Moles, however, show no adverse affects when exposed to high levels of carbon dioxide, or conversely, low levels of oxygen, for long periods of time. Specialized blood cells affect the way hemoglobin binds to carbon dioxide, allowing them to breathe in the same air they just breathed out without any ill effects.