The phrase “blind as a bat” is a common misconception, suggesting these flying mammals are sightless. In reality, all bats have eyes and can see, though their reliance on vision varies significantly across the nearly 1,400 species in the order Chiroptera. As the only mammals capable of sustained flight, bats have evolved sophisticated sensory systems, including sight and, for many, an advanced method of environmental perception. Understanding how bats perceive their world requires examining their specialized anatomy and advanced use of sound.
Anatomy and Function of Bat Eyesight
The eyes of bats are structurally adapted for their nocturnal lifestyle, featuring a high concentration of light-sensitive rod cells in the retina. Rod cells function well in low-light conditions, allowing bats to perceive their surroundings even under dim starlight. This adaptation means their visual acuity is generally better than human night vision, enabling them to navigate effectively in the dark.
Most bats also possess cone cells, which are responsible for color and daylight vision. These cone cells often contain two types of visual pigments, giving bats the capacity for dichromatic color vision, similar to many other mammals. Many bat species have short-wavelength sensitive cones tuned to ultraviolet (UV) light, which aids in orientation at twilight and the detection of UV-reflective flowers or prey.
The ability to see UV light is useful for nectar-feeding bats, as certain flowers they pollinate reflect UV light, making them stand out. While their vision may not be as sharp as a hawk’s, a bat’s eyesight is a functional and specialized tool for survival in a low-light environment.
Echolocation: Navigating by Sound
Echolocation is a sophisticated biological sonar system used by most bats to sense their environment, often supplementing or superseding vision. To echolocate, bats produce high-frequency sound pulses, primarily through the larynx, though some species click their tongue. These sounds are typically ultrasonic, meaning they are above 20 kilohertz (kHz), which is beyond the limit of human hearing.
As the sound waves travel, they strike objects, and the resulting echoes return to the bat’s highly tuned ears. By analyzing the time delay between the outgoing call and the returning echo, the bat accurately determines the distance to an object. The echo provides information about an object’s size, shape, texture, and direction of movement.
This system is precise, allowing bats to navigate complex environments and pinpoint tiny moving prey like flying insects. Echolocation calls are adjusted depending on the task, such as using a rapid series of pulses, known as a “feeding buzz,” when closing in on prey. The efficiency of this sensory modality in total darkness is the main reason for the persistent myth that bats cannot see.
Visual Differences Between Microbats and Megabats
The reliance on vision versus echolocation varies dramatically between the two major suborders of bats: Microchiroptera (Microbats) and Megachiroptera (Megabats). Microbats are generally smaller and mostly insectivorous, and are the primary users of laryngeal echolocation. While their eyes are functional, they tend to be smaller, and echolocation is their dominant sense for hunting and spatial awareness.
Megabats, also known as fruit bats or flying foxes, present a strong contrast, typically possessing much larger eyes and well-developed visual centers in the brain. These bats primarily feed on fruit, nectar, or pollen and rely on excellent sight and smell for long-distance navigation and locating food. Most megabats do not echolocate at all, though one family, the Rousettus genus, uses a simple form of tongue-click echolocation only within their roosts.
The size difference in their eyes reflects their differing sensory priorities. Megabats use their acute vision to fly at dusk and dawn and find food, which is often visible as large targets. Microbats use their vision for long-distance travel, but switch to the high-resolution detail of echolocation when pursuing small, fast-moving insects. This spectrum of sensory use confirms that all bats can see, but the importance of that vision is tied directly to their ecological niche.