The star-nosed mole, a remarkable inhabitant of North America, captivates attention with its distinctive appearance. This small, semi-aquatic mammal thrives in moist, low-elevation areas, including wetlands, marshes, and along the banks of streams and ponds. Its physical traits allow it to navigate and forage effectively within its environment.
The Star-Nosed Mole’s Eyesight
Star-nosed moles possess eyes, but they are notably small and largely ineffective for detailed vision. These rudimentary organs primarily detect variations in light and dark, rather than forming clear images. Given their subterranean and aquatic habitats, sharp vision is not a primary requirement for their survival. This limited visual capacity underscores their reliance on other highly developed sensory systems.
The Remarkable Star Organ
The most striking feature of the star-nosed mole is its star-shaped organ, a sensory marvel that compensates for its poor vision. This structure consists of 22 fleshy, mobile appendages, or rays, that encircle its nostrils. These rays are covered with over 25,000 minute sensory receptors known as Eimer’s organs, making the star one of the most sensitive touch organs known in mammals.
The mole constantly moves this star, touching its surroundings up to 13 times per second to rapidly explore its environment, identify objects, and locate prey. This rapid tactile exploration allows the mole to identify and consume food items quickly, often in as little as 120 to 227 milliseconds. The central pair of appendages acts like a tactile fovea, used for detailed investigation of potential food, analogous to how an eye focuses for sharp vision.
Thriving in Darkness: Beyond Vision
Beyond the star organ’s tactile capabilities, star-nosed moles employ other senses to thrive in their dark, complex habitats. They possess a keen sense of smell, including a unique ability among mammals to smell underwater. This underwater olfaction is achieved by exhaling small air bubbles onto objects or scent trails and then rapidly re-inhaling these bubbles, which carry odor molecules back to their nostrils. Their relatively large external ear openings suggest a role for keen hearing, further aiding their navigation and prey detection. These combined sensory adaptations, along with their powerful digging abilities, enable star-nosed moles to locate invertebrates and other small prey, and navigate their extensive tunnel systems in the absence of functional vision.