Moles’ subterranean lifestyle often leads to questions about their vision, with many assuming they are blind or lack eyes. This article clarifies the reality of mole vision, exploring their eye characteristics and how they navigate their world using other highly developed senses.
The Reality of Mole Eyes
Moles do have eyeballs, though significantly reduced in size and function compared to surface-dwelling animals. These small eyes are often no larger than a pinhead and are frequently covered by fur, skin, or membranes. This protective covering shields their delicate eyes from soil and debris during tunneling.
For instance, the European mole (Talpa europaea) has eyes roughly 1 mm in diameter, often hidden beneath its fur. Some species, like the Iberian mole (Talpa occidentalis), have eyes that remain permanently closed and covered by skin. While rudimentary, these eyes can still detect changes in light and dark, helping moles discern if they have accidentally surfaced or if their tunnels are exposed.
Beyond Sight How Moles Perceive Their World
Moles use their limited vision primarily to detect changes in light, but they do not form clear images. European moles, for example, can perform light/dark discrimination tasks and will withdraw when exposed to a flashlight. Despite their poor eyesight, moles thrive in their dark environments by relying on other highly developed senses. Their sense of touch is particularly acute, especially through their sensitive snouts.
The star-nosed mole (Condylura cristata) exemplifies this reliance on touch with its unique, star-shaped muzzle, which features over 25,000 minute sensory receptors called Eimer’s organs. These organs are important for foraging and navigation, allowing the mole to rapidly identify prey and map its surroundings. Moles also possess an acute sense of smell, important for locating prey like insects and worms, orienting themselves, and communicating with other moles. Furthermore, research suggests that moles can smell in stereo, using both nostrils to create a directional map of odors in their environment. While their hearing is not as highly developed as their sense of touch or smell, moles can still detect vibrations and sounds underground.
Evolutionary Adaptations for Subterranean Life
The reduction in mole eye size and function is a classic example of evolutionary adaptation to their specialized underground habitat. In an environment of perpetual darkness, complex vision becomes unnecessary and energetically costly. Instead, energy and resources are reallocated to other traits more beneficial for a subterranean lifestyle, such as powerful digging muscles and enhanced sensory organs.
Small, protected eyes are also less vulnerable to injury from abrasive soil, roots, and debris encountered during extensive tunneling. This regressive evolution means that the genetic pathways for eye development, while still present, have undergone changes that lead to their diminished state. The traits that allow moles to detect subtle changes in their environment through touch and smell are far more advantageous for survival underground than sharp vision, explaining why these senses are so highly refined in moles.