The idea that all bats use echolocation for navigation and hunting is a common misconception. While this sophisticated biological sonar is a defining feature for the majority of bat species, it is not universal across the entire order Chiroptera. The answer lies in the fundamental biological differences between the two major suborders: the Microchiroptera and the Megachiroptera. This division highlights a significant evolutionary split in how these flying mammals perceive and interact with their nocturnal environment.
The Mechanics of Biological Sonar
Echolocation, or biological sonar, is a highly specialized sensory process that allows bats to effectively “see” with sound. The bat achieves this by emitting rapid pulses of high-frequency sound, primarily generated in its larynx, which travel outward and bounce off objects in the surrounding environment. These sounds are often ultrasonic, meaning they are above the range of human hearing, typically falling between 20 and 200 kilohertz (kHz).
The returning sound waves, or echoes, are captured by the bat’s highly sensitive ears and processed by its brain to construct a detailed, three-dimensional “sound map” of its surroundings. This acoustic information allows the bat to determine an object’s distance, size, shape, and texture with remarkable accuracy. The time delay between the pulse emission and the echo return is what provides the distance measurement.
Bats utilize two main types of calls, sometimes in combination, to gather different kinds of spatial data. Constant Frequency (CF) calls maintain a single pitch and are effective for detecting the movement and velocity of targets through the Doppler shift phenomenon. Frequency Modulated (FM) calls, in contrast, sweep rapidly from high to low pitches, providing excellent resolution for determining the object’s range, location, and fine detail. By combining these call types, bats can optimize their sonic toolkit for both long-range detection and precise, close-range maneuvering.
Microbats: The Echolocation Specialists
The suborder Microchiroptera, commonly known as microbats, comprises the vast majority of all bat species, and nearly all of them are specialists in laryngeal echolocation. These bats are generally insectivorous, making the ability to detect and track small, fast-moving prey in complete darkness necessary for survival. Their highly sophisticated sonar allows them to navigate complex, cluttered environments, such as dense forests or cave systems, and efficiently capture insects mid-flight.
As a bat approaches a target, it rapidly increases the rate of its echolocation calls, a phenomenon known as the “feeding buzz,” which provides continuous, updated information for a precise interception. Some microbats are even capable of using a quieter “whispering” technique to focus on prey echoes and reduce clutter from the surrounding vegetation. This refined acoustic perception allows them to distinguish between an insect and a leaf, even when the prey is stationary on a surface.
Megabats: Reliance on Sight and Smell
The suborder Megachiroptera, also known as flying foxes or fruit bats, represents the primary exception to the echolocation rule. These bats, which are typically much larger than microbats, generally lack the laryngeal apparatus required for the sophisticated, high-frequency sonar. Instead, megabats primarily use two other highly developed senses for orientation and foraging: vision and smell.
Flying foxes possess relatively large eyes with excellent low-light vision, which they use to navigate through open spaces and locate prominent visual landmarks. Their diet mostly consists of fruit, nectar, and pollen, which they locate using a keen sense of smell, aided by large olfactory bulbs in their brain. This reliance on sight and smell is energetically more efficient for their lifestyle, which often involves flying long distances to find patches of ripening fruit.
There is one notable exception within the megabats: the genus Rousettus, which includes the Egyptian fruit bat. These bats do echolocate, but they do so using a simple system of sharp, audible clicks produced by their tongue, not their larynx. This rudimentary tongue-click sonar is primarily used for navigation within the pitch-black confines of their cave roosts, while they still rely on their sight and smell for long-range travel and foraging outside.