The common saying “blind as a bat” is a misconception. These nocturnal mammals are not blind; they possess sophisticated sensory abilities. While echolocation is their most renowned sense, bats also have functional eyesight, providing a comprehensive understanding of their surroundings.
Understanding Bat Eyesight
Bats have functional eyes and see well, especially in low-light conditions. Their eyes are adapted for nocturnal life, featuring large pupils and many rod cells specialized for detecting movement and light intensity variations. This allows them to navigate effectively during twilight and night. Some bat species perceive ultraviolet (UV) light, useful for finding UV-reflecting flowers. While not all bats have color vision, many see in the middle and long wavelengths (green, yellow, red).
How Echolocation Works
Echolocation is a primary sensory system for many bats, allowing them to “see with sound.” Bats emit high-frequency sound waves, called ultrasonic calls, beyond human hearing. These waves travel outwards, bounce off objects, and return to the bat’s sensitive ears as echoes. The bat’s brain processes these echoes, interpreting information about distance, size, shape, texture, and movement, creating a detailed “sound map.” This ability is important for navigating cluttered environments and locating prey in darkness.
Vision and Echolocation Working Together
Vision and echolocation often work in concert for bats. Bats use both senses in different situations, or simultaneously, for a complete sensory picture. Echolocation is effective for detailed navigation and hunting in darkness, allowing bats to detect objects as fine as a human hair. Vision can be used for long-distance orientation, detecting silhouettes against the sky, or navigating in ambient light. Egyptian fruit bats, for example, use echolocation even in daylight, complementing their excellent vision with precise distance information.
Diverse Sensory Strategies Among Bats
Reliance on vision versus echolocation varies across bat species, reflecting their ecological niches. Microbats, typically insect feeders, are known for their reliance on echolocation for hunting and navigation. While their eyes are smaller, they use vision for detecting large obstacles and navigating over longer distances. In contrast, megabats, such as fruit bats, often have large eyes and rely primarily on vision and smell to locate food and navigate. Some fruit bats, like the Egyptian fruit bat, also echolocate using tongue clicks, a unique adaptation.