Dolphins are common creatures at rivers and seas. Majority of small toothed whales are dolphins. Dolphins are large sea animals making it part of the cetaceans, where whales and porpoises belong (Stoops, 1996). Dolphins belong to family Plantanistidae and Delphinidae, respectively. Often, people used dolphins and porpoises interchangeably denoting same species but porpoises in particuclar and dolphins are different species. Porpoises belong to family Phocaenidae; it has a rounded snout and chisel-liked teeth.
While dolphins are under family Plantanistidae and Delphinidae, instead of a rounded snout, dolphins have beak like snout and sharp, conical teeth (http://www. dolphinlovers. com/facts. php) Fig. 1 Comparison between the snout of a porpoise and a dolphin Dolphins are outgoing creatures; often they are mingling in a group with two to fifteen animal members or more. Most of their communities are dominated by females, its offspring, sisters and other females.
Subadult male dolphins will leave these female-dominated communities to start a group of “bachelor” dolphins; if these dolphins become sexually mature, they can move in the female groups for copulation. These mammals are very playful. They are often spotted riding the bow wave or stern wake of boats and “surfing” on waves. Chasing and tossing things to one another is one of their favorite plays. If seen jumping or breaching, it indicates enthusiasm for these creatures. Play is important for dolphins for learning and as well as to practice their skills necessary for their life’s survival (Geocities.
com, 2006). Communication among marine animals, dolphins in particular are extensive and complex. The current paper focuses on these creatures’ characteristics, particularly their capability to engage in echolocation. Dolphins can see their environment like that of an X-ray machine and thereby transmitting this x-ray like images to other dolphins. If sight is very crucial for land animals, dolphins use a sound “seeing” system called echolocation. Echolocation is a sensory sonar system used by dolphins for communication purposes and for locating things in their environment.
Through the sound waves released and listened to – size, shape distance speed direction and internal structure of an object is determined. This sound seeing system provides information such as water depth and the position of food and rocks making it effortless for them to catch their prey. (http://www. botany. uwc. ac. za/Envfacts/facts/dolphins. htm, 2007). Scope The paper begins with an introduction about the dolphin, and their general characteristics as sea creatures.
This is followed by a discussion of their general physiology, including their skin, fin, swimming speed, breathing, and body temperature. The dolphin family is then discussed, with its 33 species – with 5 river species and 6 porpoise species. Of these, the most popular is said to be the bottlenose dolphin which are found in theme parks and are featured in television programs. The next focus would be on the dolphin’s brainpower, speficically in their capacity to make tunes among themselves with a wide range of sounds. Their distinctive communication patterns are likewise expounded on.
The paper concludes with a call for concern and protection from humans, who are supposed to be stewards of these creatures. Overview With regards to its general physiology, dolphins have rubbery skin. They are classified as mammals and have the capacity of maintaining high body temperature. They can hold their breath for several minutes making it easy for them to have rapid and deep dives of more then 300 m (1,000 ft). To date, there are more than 33 different species of dolphins, over 5 different species of river dolphins and more than 6 different species of porpoises.
Though there are many species of dolphins, the most popular are bottlenose dolphins which are frequently featured in television and theme parks. Perhaps their greatest strength is their ability to communicate with one another or to echolocate. This is the counterpart of language among humans. Dolphins create whistles and sounds signifying an action for which another dolphin can understand, it can signal danger for their kind hence they should be alert or a prey is near at hand thus, everybody must prepare; depending on the whistle produced.
They can make signature whistles that carry distinct information. Considering the cognitive abilities of bottlenose dolphins, their vocal learning and copying skills, and their fission–fusion social structure, their communication process can be further studied to provide evidences about their “dolphin messages and echoes. ” Humans have the responsibility of taking care of these creatures, acting as their stewards to prevent them from extinction. General Physiology of a Dolphin A dolphin’s body is smooth having a rubbery-feel of its hairless skin when touched.
The skeletal remnants of five digits in the front appendage form the flippers mainly acting as its balancer during its swim. The rear appendages are almost absent because the small pelvic bones are deep-rooted in the connective tissue at the base of the tail (Dolphin Lovers. com, 2006). The subcutaneous dermal tissue of the dolphin forms its immovable dorsal fin; its tail fin is also dermal in its origin. Its movement is similar with the whales wherein the major force comes from its vertical oscillations of the tail and flukes making it capable to swim at a speed of 37-40 km/h, and in some events, its swimming speed reaches up to 48 km/h.
Dolphins seem restless in traveling the rivers but in reality, it rides the bow wave by making use of the ship’s trust (Stoops, 1996) Dolphins are mammals, hence breathing and maintaining high body temperature is vital. Dolphins maintain its internal temperature at 36. 5 deg to 37. 2 deg C (97. 9 deg to 99 deg F), with its thick layer of dense fat (blubber) under the skin. At the top of its head, a single nostril or blowhole is placed where it acts as its lungs. Dolphins breathe air at the surface every two minutes consisting of brief unpredictable exhalation followed by a longer inhalation.
Dolphins are capable to hold their breath for several minutes making it easy for them to have rapid and deep dives of more then 300 m (1,000 ft) (Dolphin Lovers. com, 2006). Their swimming capabilities attribute to its powerful tail and the special function of its skin. Due to their streamlined body contour enabling them to have rapid movements and deep dives in the sea like most marine animals. Fig. 2 General physiology of a dolphin The Dolphin Family There are more than 33 different species of dolphins, over 5 different species of river dolphins and more than 6 different species of porpoises (Geocities.
com, 2006). Fig. 3 Some Species of the Dolphin Family Though there are many species mentioned, bottlenose dolphins (Tursiops truncatus) are the most familiar species. It gained popularity because it has been a mainstay of TV programs. Also, people have the chance to meet and greet bottle nose dolphins at ocean-theme parks. The biggest dolphin specie is the one seen in the movie “Free Willly”; Orca (Orcinus orca) or the killer whale where the males can grow up to 9. 6 meters http://www. dolphinear. com/data/dolphin_species. htm Fig. 4. Picture of Orca and the Bottlenose Dolphin
Dolphin’s Brainpower Greco and Gini (2005) say that dolphins are capable of making tunes among themselves with a wide range of sounds. Dolphins show evidence that their intelligence is greater than that of dogs. Dolphins learn easily and execute complicated tasks, continuous communications with one another, and their ability to mimic the sounds of human language if they are given ample time to be trained. Toothed whales have exceptionally large brains including the famously bright dolphins that have capabilities previously only attributed to humans and apes.
Cetaceans (dolphins, whales and porpoises) and its ancestors acquired changes specifically in their brain through evolution. One of the reliable evidence to support this claim is by measuring the level of encephalization of a species or a taxonomic group. EQ is the measure of observed brain size relative to expected brain size derived from a regression of brain weight on body weight for a sample of species. EQ measures how much larger or smaller a species’ total brain size is from what is expected based on brain-body allometry (Greco et. al, 2003).
Dolphins and humans share many common attributes. Both creatures are mammals wherein the young are born alive and not hatched from eggs. Air is important for both organisms since it sustains their breathing; the only difference is that dolphins must come up to the surface to breathe in its blowhole on the top of its head and when it dives, the blowhole closes unlike humans that continuously breathe air in its respiratory system. Wang (1995) asserts that aside from being mammals, communication is one the major attributes keeping these two organisms at par with one another.
Humans are capable of language and speeches denoting an idea or message for a particular person while dolphins create whistles and sounds signifying an action for which another dolphin can understand, it can signal danger for their kind hence they should be alert or a prey is near at hand thus, everybody must prepare; depending on the whistle produced. Fig. 5 Illustration of the brain size of (a) archaeocete, Cetacean’s ancestor (b) dolphin Distinctive Communication of Dolphins The capabilities of different organisms are astounding particularly in identifying objects from a far.
The association between object characteristics such as visual shape, and sensory characteristics like retinal projection, is unclear. The processes on how these characteristics work hand-in-hand remains imprecise. Dolphins communicate by making two types of sounds: vocalizations and echolocation are the two sounds produced by dolphins for communication. Vocalizations are the squeaking sounds from the blowhole that is often heard by humans which is used by dolphins to communicate.
Echolocation also called sonar, is a distinctive ability of dolphins to locate and discern objects down under (Janik, 2000). A dolphin releases a particular sound and listens for the echo allowing dolphins to travel under dark waters without bumping or hitting into anything. As much as 1,200 clicks/ sound can be produced in a second and can be transmitted in advance These clicks are from the rounded forehead of the dolphin, melon; along with its lower jaw filled with jelly-like substances for sound waves amplification.
When a dolphin swims, the head is moved back and forth to skim through its surroundings, while the echoes are send out to bounce off objects aiming at the lower jawbone, returning sound waves to the inner ear, and this whole process occur rapidly, similarly to how fast a human brain decodes if the individual accidentally touches a hot object. The pitch of the returning echo and the time it takes to get there is important so the dolphin can determine the shape, size, speed, texture, and density of the object; even inside of an object, almost like an X-ray (McCowan, 2001).
Echolocation is not solely for communicative processes; it also serves the purpose of locating preys, other dolphins, predators, a lost baby or a sick dolphin. Through echolocation, it allows dolphin to explore its water world wherein sight is of little use. Also, echolocation entails fast analysis of the sound being heard as to what message is conveyed by the dolphin who send the sound (http://www. dolphins-and-more. com/dolphins-echolocation. html)
If a dolphin makes a sound, the sound bounces off into objects and creatures then it bounces back in the dolphin’s direction who is going to receive the sound and the information given by it when its sonar receives it. The dolphin’s brain comprehends the message obtained, hence the dolphin will respond accordingly to the message. Echolocation provides vibrations, their frequency, the level of energy, the distance and if the object is moving or not is very important. With these factors interacting, it creates varied “dolphin messages” (Tyack, 2000).
Echolocating dolphins serve as models for object recognition sonar systems. The association between echo characteristics and object characteristics was given emphasis. A dolphin may keep ‘sound templates’ in its brain and be able to recognize whole objects through listening for a particular sound. A dolphin’s brain may contain algorithms, resulting through natural endowments or experience or both, allowing it to identify object characteristics based on sounds (Wells et. al, 1987). Bottlenose dolphins are capabe of producing low frequency sounds ranging between 0.
25 to 150 kHz. Higher frequencies range make up echolocation; low frequencies sounds which is produced often are for social interaction, these low frequency signals can travel greater distance compared to that of higher as the signals travel much further distances. These frequency ranges are correlated with the amplitude obtained from studies of dolphins (Hoelzel, 2002). Click sounds are usually 40-70 microseconds, though short, these clicks are loud reaching around 220 decibels. Click trains are the sound sproduced by dolphins.
It is consist of hundred or throusand of clicks per second which are high in frequency. High frequencies don’t travel as far as low frequencies, these high frequencies with very short wavelengths permit dolphins to echolocate on small objects and scrutinize the detail of an object. High frquency and the fine details of an objetc are directly proportional as such the higher frequecy produced, it would allow the dolphins to further examine the object at hand; also, it allows them to track their prey faster(www. dolphinpod. com).
The localizing system ability of the dolphin Tursiops truncatus in discerning the characteristics of an object moving in radial motion was studied. The thresholds of the animals’ threshold sensitivity at its target were given focus. The speed and acceleration were measured respectively (2. 6 cm/sec) (0. 6 cm/sec2). For a target moving at a constant speed, dolphins used probe signals made of two impulses. If targets are said to be accelerating, impulses composed of three signals are used. These methods are proven effective for technical methods concerning hydrolocation and radiolocation.
hydrolocation and radiolocation (Zhukovski et. al. , 2004). The dolphin’s wave production and sound is inversely proportional; for every wave production, the sound decreases by only 4 µ sec/decibel (dB). Low-frequency clicks (6-kHz peak power) are equivalent with three times increase far-reaching 12 µ sec/dB. The dolphin brainstem is capable of tracking individual click/ 6oo seconds. The latency and amplitude are inversely proportional (as latency is increasing, amplitude decreases) with increasing click rates. This proportionality may vary depending on the wave production of dolphins.
The dolphin’s brain is capable of processing short frequent clicks. The wave production in correlation with latency and frequency as well as click production can further test the sonar signal processing of dolphins (Ridgway, 1981). The echolocation process – sending out clicks and listening to the click echoes – is what produces a kind of mental image of the object that a dolphin is investigating with clicks. We know that the changes in the structure of the click echoes are what a dolphin uses to form this mental image, although it is still an unsolved mystery exactly how they manage to accomplish it.
This echolocation ‘image’ is unlikely to be something that a human being could imagine simply because people can’t echolocate. But, this “mental image” is currently the best analogy we’ve got. Scientists have learned from experiments with dolphin echolocation that their acoustic image is quite detailed, and allows a dolphin to do some pretty amazing things Real targets are used to study dolphin echolocation. Classifying the echo parameters is very difficult due to various factors affecting such as physical dimensions and the reflection characteristic of real targets.
Dolphin echolocation sounds are transformed into artificial echoes, which are played back to the animal. The phantom echo system, a digital sound processing is used to make echo analysis easier. Echoes of several underwater targets were simulated to evaluate the quality of the method (Aubauer and Whitlow, 1998). In bats and technological sonars, the gain of the receiver is increased with time after the transmission of a signal to balance off for the lost acoustic circulation. The current understanding of dolphin echolocation reveals that automatic gain control is not a part of dolphin’s sonar system (Tyack, 2000).
Field measurements of free-ranging echolocating dolphins were tested and the results showed that dolphins do have automatic gain control mechanism which is put into practice during transmission phase rather than the receiving phase of a sonar cycle. The amplitude of the dolphins’ echolocation signals are highly range dependent; this amplitude increases as the target increases, R, in a 20 log(R) fashion to compensate for propagation loss. If a school of fishes, with plenty of sound distributors would be the echolocation target, the echoes from the school will be nearly constant with range as the dolphin closes in on it.
This characteristic has similar effect as time-varying gain in bats and technological sonar when considered from a sonar system perspective (Wells et. al, 1987). Echolocation – or biosonar is an auditory imaging system used by various species for navigation and for tracking their prey in their vicinity particularly that their eyesight is incapble of helping them. Emission of vocalizations by the echolocating animal are emitted, detecting the echoes of those sounds and uses them to produce three-dimensional information about the environment. Also, these sounds help dolphins to be aware of their environment, preparing for an enemy attack (www.
dolphinpod. com). Toothed whales, small mammals such as rats and shrews uses echolocation. These organisms comprehend their environment via the interpretation of acoustic reflections. In other words, echolocation is not just an ordianry auditory scene analysis, itrequires specialized neural mechanisms and complex computations for the oragnism to be able to understand the message given by the sender and to intrepret it corretly by the receiver. The neural circuitry underlying echolocation allows for the perceptual organization of auditory information, which guides complex spatially-guided behaviours.
(www. seaworld. org). Whistles, buzzes, qucks and pops are the sounds produced by dolphins associated with travelling, socializing and feeding. Specific sounds are produced for a specific behavior which is also associated with changed in season. Pops are signifies feeding; quacks are for socialization; buzzes are for travelling purposes. During summer, dolphins are busy socializing with other dolphins and travelling for food hunt while during fall, dolphins are preparing for migration (Jacobs et. al, 2003).
Smolker and Pepper (1999) state that dolphins are eager to learn new vocalizations (whistles) throughout life. Over a 4 yr study period, three male bottlenose dolphins are subjected to form an alliance, to herd female dolphins. Among individuals, whistle sounds produce are varied. The distinctiveness of individual repertoires decreased, the sounds produced by the three bottlenose dolphins became indistinguishable, because some whistles were shared among each other. By the end of the study, the three bottlenose dolphins had a common whistling sound which was never heard before the alliance was started.
The frequency modulation pattern of the signature whistles of each dolphin contains sufficient information for specificity but the information received is used by the receiver to identify individuals. Dolphins do not have individual voice features but the sound production is greatly affected by changing water pressure (Janik, 1999), make voice recognition underwater more complex than that in the air. Also, the pitch and the time travel of the whistle or the sonar produced is also affected. Animals identify each other’s whistles individually rather than just purely differentiating them.
Recognition means perceiving something to be similar with an idea or learning that is previously known. Bottlenose dolphins identify themselves with a signature whistle. However, scientists have found no evidence of a dolphin language. A mother dolphin may whistle to her calf almost continuously for several days after giving birth. This acoustic imprinting helps the calf learn to identify its mother (Caldwell, Caldwell, and Tyack, 1990). Discrimination can also be used but it does not need previous learning from comparison purposes. The animals differentiate stimuli among them because animals are biased for one class of stimuli.
The biases are mainly family based on a preference for an underlying feature in the modulation pattern used by related individuals. The other explanation is that the animals recognize the preferred stimulus individually particularly if the stimuli was encountered before clarifying previous confusion around the role or even existence of signature whistles (Janik, 1999,Tyack, 2000 and McCowan, 2001). Dolphins ability to and identity information in synthetic signature whistles that had all voice information removed demonstrates that the contour carries such signature information and that this information is used by the receiver.
Janik and Slater (1998) argued that the need for individual recognition and group cohesion are the two key factors for the evolution of vocal learning in dolphins. Vocal learning enhances interindividual variability of signature whistles while maintaining potential group, population, or species features in the signal. In signature whistle development, a baby dolphin tends to duplicate the whistle that it only heard rarely adding slight modifications ending up as its own signature whistle (Fripp, et. al, 2005). This process leads to individually distinctive signature whistles.
Geographic variation in whistle parameters over longer distances can also be a factor, the whistles produced by the dolphins at Ganges River are far different from those whistle sounds produced by those at Amazon River, or modifications are already done making each whistle sound unique (Wang,1995). However, the largest dolphin species, the killer whale (Orcinus orca), uses group-specific dialects in its communication system (Ford, 1983). Although vocal learning has evolved in one particular context, it can be used for other purposes once it is established. For example, learning also allows duplication of signals in direct social interactions.
Dolphins frequently imitate each other’s whistles in the wild (Wells. et. al, 1987). These signature whistles carries identity information independent from voice features portray the possibility of using these as referential signals, either addressing individuals or referring to a group, similar to the use of names in humans. Given the cognitive abilities of bottlenose dolphins (Janik, 1999), their vocal learning and copying skills, and their fission–fusion social structure, their communication process can be further studied to provide evidences about their “dolphin messages and echoes.
” Personal Conclusion All creatures have their own way of communication to their fellow species. Communication and echolocation among dolphins needs further study and experimentation. The processes involved in both communication (whistles) and echolocation are already established but the different factors affecting it are yet to be known. Dolphins have their unique sound, when calling a buddy and same with a mother dolphin calling her young. A mother dolphin whistles to her calf almost continuously for several days after giving birth.
This acoustic imprinting produced by the mother dolphin helps the calf learn to identify its mother. Dolphins regulate their sounds by shunting air throughout the air sacs beneath the blowhole. Tissue structures in this area slap together (much like a trumpet player’s lips) to produce the clicks. These sounds often extend into the ultrasound region. The whistling sound and the echoes emitted aids dolphins in their survival. The problem lies if the whistling signal denotes individuality or whether it is just a modification of a whistling sound heard within the surroundings.
Other factors such as geographical variation, pitch, waves and others can alter the sound produced. It is just so amazing that despite these factors which need to be further studied, the communication processes among dolphins continuously exist. The meaning of the message is not altered despite the mentioned factors. Also, hundred clicks (sounds) can be produced by dolphins within a second but they are able to produce the correct whistle for a specific event and thus the receiver dolphin reacts accordingly.
Aside from the clicks produced, neural activity is still studied on how dolphins can accurately compute the frequency of the clicks emitted for them to understand the message. The whistling communication process among dolphins makes them unique among other sea creatures. Echolocation helps them to locate objects since vision would not be adequate in locating objects down under; also helping them to avoid bumping into other objects like seaweeds and corals. Whistles and echoes are the counterpart of speech and language for humans.
Humans’ brains and that of dolphins are relatively of the same size. Neural activity frequency computation still remains unclear. Though many computations had been published, it still seems inadequate to explain the processes involved within the dolphin’s brain. Also, it is fascinating how these control the sound emitted. Despite the factors affecting their communication such as season, water depth, noise pollution, geographic variation their system of communication never failed. Whether it be on great depths of water, the receiver had been effective in sending his message to the receiver.
Humans and dolphins are relatively similar but would that be enough to support the conclusion that organisms with bigger brain structure are capable of communicating with one another? Does it follow that complexity is proportional with brain size? Is it safe to assume that humans and dolphins are closely related? Dolphins in Danger Dolphins are indeed lovely sea creatures. It entertains us in its own ways. And often, meaningful association between humans and these sea creatures may develop just like in the movies we watch.
It is just unfortunate that man harms these lovely creatures as we pollute and destroy their habitats to serve our own purpose. Human beings are the most complex life forms and we must take the responsibility of protecting these friendly sea creatures. Dying Dolphin and Porpoise References Aubauer, R. and Au, W. (1998). Phantom echo generation: A new technique for investigating dolphin echolocation. Journal of the Acoustical Society of America. 104(3). 1165-1170. Caldwell, Melba C. , David K. Caldwell, and Peter L. Tyack. “Review of the Signature-
Whistle Hypothesis for the Atlantic Bottlenose Dolphin. ” In The Bottlenose Dolphin, edited by Stephen Leatherwood and Randall R. Reeves, pp. 199-234. San Diego: Academic Press, Inc. , 1990. Dolphin Lovers. com (2006). Dolphin facts. Retrieved February 23, 2007 from http://www. dolphinlovers. com/facts. php. Dolphinear. com. (2006). Dolphin ear. Retrieved 24 February 2007 from http://www. dolphinear. com/data/dolphin_species. htm. Ford, J. K. B. & Fisher, H. D. (1983). In Communication and behavior of whales. Payne, R (ed. ). Westview, Boulder, 129–161.
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