The common saying “blind as a bat” suggests these nocturnal creatures lack the ability to see. This belief is inaccurate. Bats possess sophisticated sensory capabilities, including vision, that allow them to navigate and thrive. While their perception differs from humans, bats are far from blind.
How Bats See
Bats have functional eyes, though their visual acuity varies significantly among species. Megabats, often called fruit bats, have larger eyes and rely heavily on eyesight for foraging and navigation. They distinguish colors and see ultraviolet light, helping them locate ripe fruits and flowers that reflect UV wavelengths.
Microbats, known for their reliance on echolocation, also use vision. Their eyes are smaller than megabats’ but are well-adapted for low-light conditions, allowing them to perceive shapes and objects. Some microbat species have vision superior to humans in dim light, using visual cues for long-distance navigation, recognizing landmarks, and avoiding predators.
The Science of Echolocation
Echolocation is a primary sensory tool for many bat species, allowing them to perceive surroundings in complete darkness. This process involves bats emitting high-frequency sound pulses and interpreting the echoes from objects. Bats produce these ultrasonic sounds mainly through their larynx, adapted to generate intense vibrations. Some species, like horseshoe bats, emit sounds through their nostrils, often surrounded by fleshy structures that direct the sound.
Bat sounds typically range from 14,000 Hz to over 100,000 Hz, far beyond human hearing (up to 20,000 Hz). By analyzing echoes, bats construct a detailed “sound map” of their environment, determining object size, shape, texture, distance, and movement. Echo timing, pitch changes (Doppler effect), and sound intensity variations provide crucial information. This system allows bats to detect objects as fine as a human hair and hunt flying insects, increasing their pulse rate to 200 pulses per second when closing in on prey.
Other Amazing Bat Senses
Beyond vision and echolocation, bats possess other acute senses. Their sense of smell is well-developed, playing a significant role in locating food sources, especially for fruit and nectar-feeding bats. They distinguish ripe fruits and specific flowers by scent, even where echolocation is less effective.
Bat wing membranes are sensitive, containing specialized touch receptors. This sensitivity allows them to detect air currents, pressure changes, and prey. Their hearing extends beyond echolocation frequencies, enabling them to perceive a wider range of environmental sounds, including rustling leaves or other animal calls. Some bats, like the common vampire bat, can even sense heat using specialized nerve receptors to detect warm blood vessels in prey.
Unraveling the Myth’s Origin
The myth of bats being blind likely originated from observations of their nocturnal activity and seemingly erratic flight patterns. Before understanding echolocation, people might have assumed bats flailed blindly in the dark. The phrase “blind as a bat” became a common idiom for poor eyesight, reinforcing the misconception.
However, the discovery of echolocation, largely attributed to Donald Griffin in the 1940s, revealed bats’ sensory prowess. While bats rely heavily on this unique “sound vision” for hunting and navigation in darkness, their functional eyesight, combined with other senses, shows an animal well-adapted to its environment. Their sensory world is complex and integrated, showcasing natural adaptation.