Echolocation, also called Biosonar, is the biological sonar used by several mammals such as bats (although not all species), dolphins and whales (though not baleen whales). The term was coined by Donald Griffin, who was the first to conclusively demonstrate its existence in bats. Two bird groups also employ this system for navigating through caves, the so called Cave Swiftlets in the genus Aerodramus (formerly Collocalia) and the unrelated Oilbird Steatornis caripensis. This article is about underwater sound propagation. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... “Chiroptera” redirects here. ... Genera See article below. ... This article is about the animal. ... Diversity Around 15 species; see list of cetaceans or below. ... Donald Redfield Griffin (August 3, 1915 - November 7, 2003) was an American professor of zoology at various universities who did seminal research in animal behavior, animal navigation, acoustic orientation and sensory biophysics. ... For other uses, see Bird (disambiguation). ... Genera Hydrochous Collocalia Aerodramus Schoutedenapus Bold text The birds called Swiftlets or Cave Swiftlets are contained within the four genera Aerodramus, Hydrochous, Schoutedenapus and Collocalia. ... Binomial name Steatornis caripensis Humboldt, 1817 The Oilbird (Steatornis caripensis) is a slim, long-winged bird related to the nightjars. ...

Echolocating animals emit calls out to the environment, and listen to the echoes of those calls that return from various objects in the environment. They use these echoes to locate, range, and identify the objects. Echolocation is used for navigation and for foraging (or hunting) in various environments. In audio signal processing and acoustics, an echo (plural echoes) is a reflection of sound, arriving at the listener some time after the direct sound. ... Whereas originally the term Navigation applies to the process of directing a ship to a destination, Navigation research deals with fundamental aspects of navigation in general. ... Foraging just means looking for food (or, metaphorically, anything else). ...

Basic Principle

Echolocation works like active sonar, using sounds made by an animal. Ranging is done by measuring the time delay between the animal's own sound emission and any echoes that return from the environment. Unlike some sonar that relies on an extremely narrow beam to localize a target, animal echolocation relies on multiple receivers. Echolocating animals have two ears positioned slightly apart. The echoes returning to the two ears arrive at different times and at different loudness levels, depending on the position of the object generating the echoes. The time and loudness differences are used by the animals to perceive direction. With echolocation the bat or other animal can see not only where it's going but can also see how big another animal is, what kind of animal it is, and other features as well. This article is about underwater sound propagation. ...

Bats

Microbats use echolocation to navigate and forage, often in total darkness. They generally emerge from their roosts in caves or attics at dusk and forage for insects into the night. Their use of echolocation allows them to occupy a niche where there are often many insects (that come out at night since there are less predators then) and where there is less competition for food, and where there are fewer other species that may prey on the bats themselves. The microbats constitute the suborder Microchiroptera within the order Chiroptera (bats). ... Orders Subclass Apterygota Archaeognatha (bristletails) Thysanura (silverfish) Subclass Pterygota Infraclass Paleoptera (Probably paraphyletic) Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Superorder Exopterygota Grylloblattodea (ice-crawlers) Mantophasmatodea (gladiators) Plecoptera (stoneflies) Embioptera (webspinners) Zoraptera (angel insects) Dermaptera (earwigs) Orthoptera (grasshoppers, etc) Phasmatodea (stick insects) Blattodea (cockroaches) Isoptera (termites) Mantodea (mantids) Psocoptera...

Microbats generate ultrasound via the larynx and emit the sound through the nose or, much more commonly, the open mouth. Microbat calls (help· info) range in frequency from 14,000 to well over 100,000 Hz, mostly beyond the range of the human ear (typical human hearing range is considered to be from 20 Hz to 20,000 Hz). The larynx (plural larynges), colloquially known as the voicebox, is an organ in the neck of mammals involved in protection of the trachea and sound production. ... Image File history File links Ultrasonic_bat_calls. ...

Individual bat species echolocate within specific frequency ranges that suit their environment and prey types. This has sometimes been used by researchers to identify bats flying in an area simply by recording their calls with ultrasonic recorders known as 'bat detectors'. However echolocation calls are not species specific and some bats overlap in the type of calls they use so recordings of echolocation calls cannot be used to identify all bats. In recent years researchers in several countries have developed 'bat call libraries' that contain recordings of local bat species that have been identified known as 'reference calls' to assist with identification.

Since the 1970s there has been an ongoing controversy among researchers as to whether bats use a form of processing known from radar termed coherent cross-correlation. Coherence means that the phase of the echolocation signals is used by the bats, while cross-correlation just implies that the outgoing signal is compared with the returning echoes in a running process. Today most - but not all - researchers believe that they use cross-correlation, but in an incoherent form, termed a filter bank receiver. For other uses, see Radar (disambiguation). ... Coherence is from Latin cohaerere = stick together, to be connected with). ... In statistics, the term cross-correlation is sometimes used to refer to the covariance cov(X, Y) between two random vectors X and Y, in order to distinguish that concept from the covariance of a random vector X, which is understood to be the matrix of covariances between the scalar...

When searching for prey they produce sounds at a low rate (10-20/sec). During the search phase the sound emission is coupled to respiration, which is again coupled to the wingbeat. It is speculated that this coupling conserves energy. After detecting a potential prey item, microbats increase the rate of pulses, ending with the terminal buzz, at rates as high as 200/sec. During approach to a detected target, the duration of the sounds is gradually decreasing, as is the energy of the sound.

Toothed whales

Diagram illustrating sound generation, propagation and reception in a toothed whale. Outgoing sounds are red and incoming ones are green

Toothed whales (suborder odontoceti), including dolphins, porpoises, river dolphins, orcas and sperm whales, use biosonar because they live in an underwater habitat that has favourable acoustic characteristics and where vision is extremely limited in range due to absorption or turbidity. Image File history File links Toothed_whale_sound_production. ... Image File history File links Toothed_whale_sound_production. ... Families See text The toothed whales (systematic name Odontoceti) form a suborder of the cetaceans. ... Families See text The toothed whales (systematic name Odontoceti) form a suborder of the cetaceans. ... In psychology, visual perception is the ability to interpret visible light information reaching the eyes which is then made available for planning and action. ... An underwater scene just beneath the surface. ... Turbidity standards of 5, 50, and 500 NTU Turbidity is a cloudiness or haziness of a fluid caused by individual particles (suspended solids) that are generally invisible to the naked eye, similar to smoke in air. ...

Toothed whales emit a focused beam of high-frequency clicks in the direction that their head is pointing. Sounds are generated by passing air from the bony nares through the phonic lips.^[1] These sounds are reflected by the dense concave bone of the cranium and an air sac at its base. The focussed beam is modulated by a large fatty organ known as the 'melon'. This acts like an acoustic lens because it is composed of lipids of differing densities. Most toothed whales use clicks in a series, or click train, for echolocation, while the sperm whale may produce clicks individually. Toothed whale whistles do not appear to be used in echolocation. Different rates of click production in a click train give rise to the familiar barks, squeals and growls of the bottlenose dolphin. A click train with a repetition rate over 600 per second is called a burst pulse. In bottlenose dolphins, the auditory brain response resolves individual clicks up to 600 per second, but yields a graded response for higher repetition rates. Binomial name Montagu, 1821 Bottlenose Dolphin range (in blue) The Bottlenose Dolphin is the most common and well-known dolphin. ...

Some smaller toothed whales may have their tooth arrangement suited to aid in echolocation. The placement of teeth in the jaw of a bottlenose dolphin, as an example, are not symmetrical when seen from a vertical plane, and this asymmetry could possibly be an aid in the dolphin sensing if echoes from its biosonar are coming from one side or the other.^[2][3]

Echoes are received using the lower jaw as the primary reception path, from where they are transmitted to the inner ear via a continuous fat body. Lateral sound may be received though fatty lobes surrounding the ears with a similar acoustic density to bone. Some researchers believe that when they approach the object of interest, they protect themselves against the louder echo by quietening the emitted sound. In bats this is known to happen, but here the hearing sensitivity is also reduced close to a target.

Before the echolocation abilities of "porpoises" were officially discovered, Jacques Yves Cousteau suggested that they might exist. In his first book, The Silent World (1953, pp. 206-207), he reported that his research vessel, the Élie Monier, was heading to the Straits of Gibraltar and noticed a group of porpoises following them. Cousteau changed course a few degrees off the optimal course to the center of the strait, and the porpoises followed for a few minutes, then diverged toward mid-channel again. It was obvious that they knew where the optimal course lay, even if the humans didn't. Cousteau concluded that the cetaceans had something like sonar, which was a relatively new feature on submarines. He was right. Jacques-Yves Cousteau (June 11, 1910 - June 25, 1997) was a French naval officer, explorer and researcher who studied the sea and all forms of life in water. ... The Strait of Gibraltar as seen from space. ... This article is about underwater sound propagation. ... USS Los Angeles A submarine is a specialized watercraft that can operate underwater. ...

Oilbirds

Oilbirds and some species of swiftlet are known to use a crude form of biosonar (compared to the capabilities of bats and dolphins). These nocturnal birds emit calls while flying and use the calls to navigate through trees and caves where they live. Binomial name Steatornis caripensis Humboldt, 1817 The Oilbird (Steatornis caripensis) is a slim, long-winged bird related to the nightjars. ... Genera Hydrochous Collocalia Aerodramus Schoutedenapus Bold text The birds called Swiftlets or Cave Swiftlets are contained within the four genera Aerodramus, Hydrochous, Schoutedenapus and Collocalia. ...

Echolocating shrews

Main article: Echolocating shrews

The only terrestrial mammals known to echolocate are two genera (Sorex and Blarina) of shrews and the tenrecs of Madagascar.^[4] These include the wandering shrew (Sorex vagrans), the common or Eurasian shrew (Sorex araneus), and the short-tailed shrew (Blarina brevicauda). The shrews emit series of ultrasonic squeaks. In contrast to bats, shrews probably use echolocation to investigate their habitat rather than to pinpoint food. There is evidence that a number of shrew species use echolocation. ... Species See text The genus Sorex is a group of mainly land-dwelling shrews with relatively long tails which includes many of the common shrews of Europe and North America. ... Species See text The genus Blarina is a group of relatively large shrews with relatively short tails found in North America. ... Subfamilies  Oryzorictinae  Potamogalinae  Tenrecinae Tenrecidae (common name tenrecs) is a family of mammals found on Madagascar and parts of western Africa. ... Binomial name Sorex vagrans (Baird, 1857) The Vagrant Shrew, Sorex vagrans, is a medium-sized North American shrew. ... See also Masked Shrew for the mammal known as the Common Shrew in parts of North America. ... Binomial name Blarina brevicauda (Say, 1823) The Northern Short-tailed Shrew, Blarina brevicauda, is a large shrew found in central and eastern North America from southern Saskatchewan to Atlantic Canada and south to Nebraska and Georgia. ...

See also

• Human echolocation

Human echolocation is the ability of humans to sense objects in their environment by hearing echos off those objects. ...

External links

• The British Library Sound Archive 150,000 recordings of over 10,000 species, including many echolocation recordings
• International Bioacoustics Council links to many bioacoustics resources
• Listen to Nature has bat and swiftlet sonar signals
• Bat Ecology & Bioacoustics Lab

References

1. ^ Cranford, T.W., (2000). "In Search of Impulse Sound Sources in Odontocetes." In Hearing by Whales and Dolphins (Springer Handbook of Auditory Research series), W.W.L. Au, A.N. Popper and R.R. Fay, Eds. Springer-Verlag, New York.
2. ^ Goodson, A.D., and Klinowska, M.A., (1990). "A proposed echolocation receptor for the Bottlenose Dolphin (Tursiops truncatus): modelling the receive directivity from tooth and lower jaw geometry." In Sensory Abilities of Cetaceans vol 196 ed J A Thomas and R A Kastelein (New York: Plenum) pp 255–67 (NATO ASI Series A)
3. ^ Dobbins, P. (2007). "Dolphin sonar—modelling a new receiver concept." Bioinspired Biomimicry 2 (2007) 19–29
4. ^ Thomas E. Tomasi, "Echolocation by the Short-Tailed Shrew Blarina brevicauda", Journal of Mammalogy, Vol. 60, No. 4 (Nov., 1979), pp. 751–759.

• Reynolds JE III & Rommel SA (1999), Biology of Marine Mammals, Smithsonian Institution Press, ISBN 1-56098-375-2. Authoritative work on marine mammals with in depth sections on marine mammal acoustics written by eminent experts in the field.
• Au, Whitlow W. L. (1993). The Sonar of Dolphins. New York: Springer-Verlag. Provides a variety of findings on signal strength, directionality, discrimination, biology and more.
• Pack, Adam A. & Herman, Louis M. (1995). "Sensory integration in the bottlenosed dolphin: Immediate recognition of complex shapes across the senses of echolocation and vision", J. Acoustical Society of America, 98(2), 722-733. Shows evidence for the sensory integration of shape information between echolocation and vision, and presents the hypothesis of the existence of the mental representation of an "echoic image".