Have you ever wondered how bats find their way in the dark? Or what those loud, piercing sounds dolphins make? Or the ambient clicks emitted by whales in the numerous shows and documentaries that feature them? What do they all have in common?
Echolocation or sonar—what’s the real difference?
These questions will all be addressed in this article. We will explore which species use echolocation, how scientists use special devices to detect these ultrasonic waves, conservation concerns affecting those animals, and what we can do to help.
What is Echolocation?
Echolocation is the biological equivalent of sonar technology. Various species utilize it to communicate, navigate, or sometimes both. Here’s a rough outline of how it works: the animal sends sound in a particular direction, and the sound waves reflect off objects or creatures in the path of the waves. This mechanism is extremely useful in low-light or no-light environments, whether in air or aquatic settings.
As for creatures that use echolocation for signalling, this method differs from more familiar types of communication, such as calling, singing, or grunting. Communicating with echolocation involves actively sending sound waves between creatures. This form of interaction is common among whales, which we will discuss below. In fact, creatures using echolocation are, in essence, interacting with their surroundings, both animate and inanimate.
Sound travels through air at 343 m/s at room temperature and through water almost four times faster, at a speed of 1500 m/s. The frequency of these sound waves varies with each species. The Mexican free-tailed bat (Tadarida brasiliensis) is one of the fastest, while whales are some of the slowest. Echolocation is typically measured in kHz.
(A Mexican Free-tailed bat -Tadarida brasiliensis- frequency calls is between 4 – 75 kHz) ©Michael Durham
Active Echolocation:
In active echolocation, an animal emits sound waves (such as clicks or calls) into the environment. These waves bounce off objects and return as echoes. The animal then listens to the timing, pitch, and characteristics of these echoes to determine the object’s location, size, shape, and distance.
Passive Acoustic Sensing:
While not strictly echolocation, passive acoustic sensing refers to listening to existing sounds in the environment. Some animals use this method to detect noises made by other organisms, such as prey, predators, or environmental disturbances. Unlike echolocation, no active sound emission occurs in passive acoustic sensing. While this isn’t the main focus of this article, I thought it would be useful to differentiate the two.
Species Using Echolocations:
Bats:
Twenty percent of all mammal species belong to the bat order (Chiroptera), making it the second-largest mammalian order after rodents. Contrary to popular belief, not all bats use echolocation. Seventy percent of bat species rely on this fascinating medium for hunting, navigation, and communication.
Research indicates that bats developed echolocation around 52 million years ago, during the Eocene epoch. The frequency range for bats spans from 9 kHz to 200 kHz. The maximum frequency humans can hear is 20 kHz, with the average adult unable to perceive sounds above 17 kHz. Bats use a range of sounds, including clicks, chirps, and “toks,” to echolocate.
(Many modern mammal groups appeared in the Eocene epoch. It was part of the Paleogene period which in turn was part of the Cenozoic era which was considered the ”Age of Mammals”.) ©earthathome.org
Echolocation has several functions for bats:
- Navigation :Bats use echolocation to navigate, and some migratory species use it to find their way. For example, a female Nathusius’ pipistrelle (Pipistrellus nathusii) flew 2,414 km (1,500 miles) from Russia to the French Alps, which is the longest migration recorded for this order.
- Hunting: Bats emit rapid clicks to locate insects, their primary food source. Once they pinpoint the location of their prey, they dive toward it with impressive speed and accuracy.
- Communication Different species use varying frequencies for signalling. They can even identify individuals, emotions, and characteristics through these ultrasonic signals.
- Object Identification: Bats are remarkably adept at detecting objects as small as a human hair, and can assess the dimensions of objects with a precision comparable to human sight.
(Bats are the only flying mammals. Their ears allow them to process echolocation by having two different inner ear structures that help them process echolocation signals.)
Cetaceans:
Seventy-five species of cetaceans (Cetacea) (including whales, dolphins, and porpoises) use echolocation. Most animals employing echolocation do so to navigate, hunt, and communicate.
The frequency of the ultrasound emitted by cetaceans depends on the species. For instance, bottlenose dolphins (Tursiops truncatus) emit sounds in the range of 40–130 kHz, while toothed whales (Odontoceti) produce frequencies reaching up to 170 kHz.
Cetaceans use echolocation to navigate murky or deep waters. The sperm whale (Physeter macrocephalus), a deep-diving mammal, uses echolocation at extreme depths. Bottlenose dolphins rely on slower frequencies to navigate through turbid waters.
(A Beluga whale -Delphinapterus leucas-, is one of the smartest creatures in the animal kingdom, they have even been used by the United States and Russian navies for ”spying” missions!) ©critterfacts.com
Toothed whales produce echolocation clicks through their nasal passages. The fat-filled melon in their heads focuses these clicks into a beam. The sound waves reflect off objects and are received through oil-filled channels in their lower jaw. These vibrations are transmitted to the middle ear and processed by the brain, allowing them to “hear” through their jaws!
Cetaceans are also highly social animals, employing various sounds for social communication, including clicks, whistles, and even tonal songs, particularly in humpback whales (Megaptera novaeangliae). These sounds are used for social and reproductive purposes.
Birds:
It may come as a surprise, but certain bird species also use echolocation. However, only two families of birds utilize this method: the oilbirds (Steatornis caripensis) and swiftlets (Apus species).
Oilbirds are nocturnal and use echolocation mainly to navigate in dark environments, such as caves. They produce 2–8 clicks with frequencies ranging from 7–23 kHz.
Swiftlets use echolocation in low-light or dark environments, emitting clicks between 1–10 kHz, well within human hearing range. There are 16 confirmed species of swiftlets that use this method.
(The oilbird (Steatornis caripensis) , locally known as the guácharo, is a bird species found in the northern areas of South America including the Caribbean island of Trinidad. It is the only species in the genus Steatornis, the family Steatornithidae, and the order Steatornithiformes.) ©cuevadelostayos.com ©Wikipedia.
©By wokoti – Black-Nest Swiftlet, (left). ©iStock – Edible bird’s nest. (above).
(In China having a Bird nest in a soup is a delicacy, the bird nest is mainly made up of solidified salvia from the species edible-nest swiftlets – Aerodramus fuciphagus- .)
Other Terrestrial Mammals:
In addition to bats, other terrestrial mammals use echolocation to navigate in low-light conditions. These include shrews (Soricidae), solenodons (Solenodonta), Chinese pygmy dormice (Glirulus japonicus), and tenrecs (Tenrecidae).
(The Chinese pygmy dormouse –Glirulus japonicus- is a remarkable little rodent that uses echolocation in a way that rivals bats. It emits high-pitched chirps at frequencies between 30 kHz and 70 kHz, then listens to the echoes to navigate its surroundings. This skill is especially useful at night, helping the dormouse avoid obstacles and find its way through dense forest habitats.)
< ©Joel Sartore.
Bonus: Humans:
Believe it or not, humans can also use echolocation! Studies have shown that 20–30% of blind people have learned to navigate using echolocation by tapping objects (such as their cane) or snapping their fingers. They use the returning echoes to estimate distances and detect obstacles.
©wires.onlinelibrary.wiley.com >
How Do Scientists Detect and Measure Animal Echolocation?:
To study underwater echolocation, scientists use hydrophones—devices that record sound waves from all directions. Hydrophones were first developed in 1915 for military purposes but are now used in research on marine wildlife.
Other methods include controlled experiments in aquatic enclosures, tagging animals with biologging devices to record their ultrasonic emissions, and using acoustic cameras. These cameras track and visualize sound waves using arrays of microphones or hydrophones.
(One of the interesting contraptions used to study Wild and Captive Indo-Pacific Humpback Dolphins -Sousa chinensis-.)
Concerns and How We Can Help:
Unfortunately, humans often disrupt echolocation with noise pollution. Underwater noise pollution, often called “ocean noise,” is a significant problem for marine species, especially cetaceans. Vessels, sonar, and oil drilling create loud sounds that interfere with the navigation and communication of marine life.
Above the ocean, bats face similar issues with noise pollution from traffic, construction, and machinery. Loud sounds can mask the critical echoes they rely on to hunt and navigate.
Reduce Noise Pollution: For ocean noise, vessels should slow down in busy areas, reducing engine noise. Oil rigs should be banned, and cleaner energy sources promoted.
(Hopefully, we will discuss in the upcoming articles what is considered a clean energy source, heads up, it isn’t electric cars for sure.)
Above-Ocean Noise: To reduce noise pollution on land, avoid unnecessary noise, turn off engines while stationary, and use quieter vehicles. Planting trees also helps dampen sound.
Create Quiet Zones: Establishing quiet zones where motorized vehicles are prohibited and reducing outdoor events in wildlife-rich areas can help protect animals’ ability to echolocate
I hope you enjoyed reading this article. If you have any input or suggestions, comment below in the comment section. Make sure to check out the previous articles where I covered a range of different topics, from poisonous birds to my adventure in the wilderness of Somaliland.
Till next time, remember:
Take nothing but photos, leave nothing but footprints, and kill nothing but time…
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