Everyone knows that bats and dolphins emit ultrasound. Why is this needed and how does it work? Let's see what echolocation is and how it helps animals and even humans.
What is echolocation
Echolocation, also called biosonar, is a biological sonar used by several animal species. Echolocating animals radiate signals into the environment and listen to the echoes of those calls that are returned from various objects near them. They use these echoes to find and identify objects. Echolocation is used for navigation and foraging (or hunting) in a variety of environments.
Working principle
Echolocation is the same as active sonar, which uses sounds produced by the animal itself. Ranging is done by measuring the time delay between the animal's own sound emission and any echoes returning from the environment.
Unlike some human-made sonars that rely on extremely narrow beams and multiple receivers to locate a target, animal echolocation is based on one transmitter and tworeceivers (ears). The echoes returning to the two ears arrive at different times and at different volume levels, depending on the position of the object generating them. Differences in time and volume are used by animals to perceive distance and direction. With echolocation, a bat or other animal can see not only the distance to an object, but also its size, what kind of animal it is, and other features.
Bats
Bats use echolocation to navigate and forage, often in total darkness. They usually emerge from their roosts in caves, attics, or trees at dusk and hunt for insects. Thanks to echolocation, bats are in a very advantageous position: they hunt at night when there are many insects, there is less competition for food, and there are fewer species that can prey on the bats themselves.
Bats generate ultrasound through their larynx and radiate sound through their open mouth or, much less commonly, their nose. They emit sound ranging from 14,000 to over 100,000 Hz, mostly outside the human ear (typical human hearing range is 20 Hz to 20,000 Hz). Bats can gauge the movement of targets by interpreting echo patterns from a special patch of skin in the outer ear.
Certain species of bats use echolocation in certain frequency bands that suit their living conditions and prey types. This has sometimes been used by researchers to identify the species of bats that inhabit the area. They simplyrecorded their signals using ultrasonic recorders known as bat detectors. In recent years, researchers from several countries have developed bat call libraries that contain records of native species.
Sea animals
Biosonar is valuable for the suborder of toothed whales, which includes dolphins, porpoises, killer whales and sperm whales. They live in an underwater habitat that has favorable acoustic characteristics and where vision is extremely limited due to the turbidity of the water.
The most significant first results in the description of dolphin echolocation were achieved by William Shevill and his wife Barbara Lawrence-Shevill. They were engaged in feeding dolphins and once noticed that they unmistakably find pieces of fish that silently fell into the water. This discovery was followed by a number of other experiments. So far, dolphins have been found to use frequencies ranging from 150 to 150,000 Hz.
Echolocation of blue whales is much less studied. So far, only assumptions are being made that the “songs” of whales are a way of navigating and communicating with relatives. This knowledge is used to count the population and to track the migrations of these marine animals.
Rodents
It is clear what echolocation is in marine animals and bats, and why they need it. But why do rodents need it? The only terrestrial mammals capable of echolocation are the two genera of shrews, the teireks of Madagascar, the rats, and the flint teeth. They emit a series of ultrasonic squeaks. They do not contain echolocation responses with reverberations and appear to be used for simple spatial orientation at close range. Unlike bats, shrews only use echolocation to study prey habitats and not to hunt. Except for large and thus highly reflective objects (such as a large rock or tree trunk), they are probably not capable of unraveling echo scenes.
The Most Talented Sonar Finders
Besides the listed animals, there are others capable of echolocation. These are some species of birds and seals, but the most sophisticated echo sounders are fish and lampreys. Previously, scientists considered bats to be the most capable, but in recent decades it has become clear that this is not the case. The air environment is not conducive to echolocation - unlike water, in which sound diverges five times faster. The sonar of fish is the organ of the lateral line, which perceives the vibrations of the environment. Used for both navigation and hunting. Some species also have electroreceptors that pick up electrical vibrations. What is fish echolocation? It is often synonymous with survival. She explains how blind fish could live to a ripe old age without needing sight.
Echolocation in animals has helped explain similar abilities in visually impaired and blind people. They navigate in space with the help of clicking sounds they make. Scientists say that such short sounds emit waves thatcan be compared to the light of a flashlight. At the moment, there is too little data to develop this direction, since capable sonar among people is a rarity.
