Bats are among the most misunderstood mammals, largely due to the pervasive myth that they are blind. Bats possess the necessary biological equipment to see and use vision constantly. While they are primarily nocturnal, meaning they are most active during twilight and at night, their eyes are functional and contribute to navigation. The true answer to whether a bat can see during the day is yes, but their visual system is optimized for a different environment than the one humans prefer.
Addressing the Myth: Bat Sight and Daytime Vision
The phrase “blind as a bat” is inaccurate, as all bats have eyes and the capacity for sight. Their visual acuity varies greatly across the over 1,400 species, but even the smallest insect-eating bats (microbats) rely on sight for general orientation. They use vision to detect large landmarks, such as mountain ranges or bodies of water, which helps them navigate long distances between roosts and foraging areas.
For species like the large fruit bats (megabats), vision is their primary sense. They possess relatively large eyes that grant them better eyesight than humans, especially in low light. These species often do not use echolocation at all, relying instead on sight and a keen sense of smell to locate food. Even for echolocating microbats, sight remains important for detecting obstacles beyond the effective range of their sonar, which typically extends only about 10 to 20 meters.
While bats can see in full daylight, their vision is optimized for the low-light conditions of dusk and dawn (mesopic vision). Bright, direct sunlight can be inefficient for their specialized eyes. Some bats possess the ability to see ultraviolet (UV) light, which aids in locating UV-reflective flowers and fruits, providing a visual advantage that humans lack.
The Primary Tool: How Echolocation Works
For many bat species, particularly insectivorous microbats, sight is secondary to their advanced system of echolocation, a form of biological sonar. The process begins when the bat emits rapid, high-frequency sound pulses, often through its mouth or nose. These pulses are in the ultrasonic range, meaning they are well above the limit of human hearing.
As the sound waves travel outward, they bounce off objects in the environment, creating echoes that return to the bat’s finely tuned ears. By precisely measuring the time it takes for the echo to return, the bat can calculate the distance to the object. Changes in the frequency of the returning echo, known as the Doppler shift, allow the bat to determine the speed and direction of moving prey, such as flying insects.
Echolocation is so precise that a bat can determine the size, shape, and texture of an object, enabling it to detect prey as small as a mosquito or a strand of human hair. When a bat detects a target, it rapidly increases the frequency of its calls to a “feeding buzz,” sometimes exceeding 160 clicks per second, to pinpoint the prey’s location. To prevent hearing damage from its own loud calls—which can reach 140 decibels—the bat contracts tiny muscles in its middle ear, dampening its hearing temporarily just before emitting the sound pulse.
Specialized Eye Anatomy for Low Light
The visual differences between bats and humans are rooted in the structure of the bat retina. Like all mammals, bat retinas contain two types of photoreceptor cells: rods and cones. Rod cells are highly sensitive and function best in low light, detecting light intensity but not color or fine detail.
Bat retinas are overwhelmingly rod-dominated. This high concentration of rods maximizes the eye’s ability to capture the few photons of light available in darkness, granting them superior night vision compared to humans. In some species, rods can account for over 97% of all photoreceptors.
More recent studies confirm the presence of a small population of cone cells in all studied species. Cones provide color and high-resolution vision, but are present in low densities. This limited cone population gives bats the potential for some color distinction, often in the dichromatic range, and is primarily useful during the dimmer light levels of twilight.