DOLPHINS
bottlenose dolphin Dolphins are sea mammals that arguably have the closest spiritual, intellectual and social link to humans of all sea creatures. Many people have said if they could come back as an animal they would choose to be a dolphin. Like otters, dolphins are regarded as intelligent and fun loving animals. In some cases this is a true, but they can also be aggressive and unpredictable and their habits and behavior are far from understood. [Sources: Jack MacClintock, Discover, March 2000;Kenneth Norris, National Geographic, September 1992 ┺ ; Edward J. Linehan, National Geographic, April 1979 ⊗; Robert Leslie Conley, National Geographic, September 1966 ┵]
Dolphins, porpoises and whales are members of mammalian Cetacean family. There are 83 cetacean species. They include dolphins, porpoises, pilot whales, bottlenose whales and killer whales. The 37 species of dolphins (32 sea-going species, 3 river species and killer whales). There are six species of porpoise.
Porpoises are distinguished from dolphins in having teeth that are flat, like chisels, instead of round, like pegs. Dolphins have conical teeth, a defined beak, a pronounced bulbous forehead, a more streamlined body, and a curved dorsal fin while porpoises have spade-shaped teeth, a rounded head and triangular dorsal fins. They are also generally smaller than dolphins.
Websites and Resources: National Oceanic and Atmospheric Administration noaa.gov/ocean ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Ocean World oceanworld.tamu.edu ; Woods Hole Oceanographic Institute whoi.edu ; Cousteau Society cousteau.org ; Montery Bay Aquarium montereybayaquarium.org
Websites and Resources on Fish and Marine Life: MarineBio marinebio.org/oceans/creatures ; Census of Marine Life coml.org/image-gallery ; Marine Life Images marinelifeimages.com/photostore/index ; Marine Species Gallery scuba-equipment-usa.com/marine
Britain-based Whale and Dolphin Conservation Society.
Dolphin Characteristics
Dolphins have lived to be 55 in captivity and are believed to live around the age of 30 in the wild. The distinct dolphin "smile" is a manifestation of the natural curve of the animal’s jawline not a friendly disposition. It is the result of a flared jawbone, which serves as an ultra-sensitive ear.
Dolphins have blowholes about the size of a quarter with inner valves and out outer valves to seal out water when the dolphin is under water. When they surface dolphins inhales four to ten liters of air in one second. They can blow bubbles from their blowholes. Bottlenose dolphins come to the surface an average of once every 28 seconds to breath. In aquariums they have been observed making rings and other shapes with bubbles and playing with them. ⊗
Dolphins and whales have hair and blubber — milky, white fat underneath a animal’s skin. Like whales, dolphins have a horizontal fluke rather than vertical tail fins like fish. Dolphins propel themselves forward by moving their fluke up and down. A subdermal sheath is attached to the dolphin’s muscles and skeleton. Dolphins are able to keep their skins clear of parasites that attach to whales through special features in their skins: nanometer-size ripples and ridges with a gel-like coating. Scientists are studying dolphin skin for clues on how to keep ships clear of barnacles and tubeworms ┵
Dolphins have several stomachs, like cows, which may be remnants from its terrestrial ancestors that lives tens of millions of years ago. Dolphins collect salt in their kidneys like camels.
Dolphin anatomy
Dolphin Swimming, Diving and Jumping
Dolphins swim up to 100 miles a day, jump 15 feet straight up, and can reach speeds up to 20 mph for short bursts. Some boaters have claimed they have seen dolphins traveling over 40 mph. Scientists say that in these cases the dolphins were probably getting a boost from the boat's bow wave. ┺
Dolphins can reach high speeds because they flex back and forth like spring-loaded pogo sticks. As they lift their tail, blubber on the top side is compressed and stretched, storing energy for spring-loaded down stroke. As the muscles relax compressed blubber springs back and help push the tail down.
Dolphins have been recorded diving up to depths of 1,700 feet. Bottle nose dolphins can dive to a depth of around 500 feet. Seals, whales and dolphins all relax when diving, allowing them to reduce oxygen consumption and dive deeper and stay submerged longer. The collapsible rib cage that dolphins have pushes all of the air out of their lungs which keeps them from getting the bends.⊗
spinner dolphins
Scientists have long wondered exactly how dolphins, whales and seals can stay under water so long. The secret seems to be that they float rather than swim downwards to conserve energy and do not use up oxygen unnecessarily. The stay as still as possible on the way down and use their energy to catch prey and swim back up. Whales, seals and dolphins all seem to use the same strategy. Scientists were able to observe his phenomena by strapping critter cam cameras on bottlenose dolphins, Wendell seals and even a blue whale.
Dolphin Behavior
Dolphins are well known their playfulness. Dolphins are often seen leaping high out of the water and doing flips. The can reach heights of over 15 feet and also "tail-walk" across the water by beating their fluke back and forth near the surface of the water. Some dolphins spyhop — rear up out of the water to look around — presumably to see if predators or prey is around. Trained dolphins have been taught do multiple flips and twirls, and wave at the audience with their flukes and fins.
Dolphins often ride and leap out from bow waves created by large ships. Their superb swimming and navigation skills keeps them from hitting the ships. Some dolphins like to do this and some don't. Dolphin scientist Randall Wells told Discover, "They're definitely individuals; they have their own ways of doing things. Some will quickly come up to the boat and some never do. Some will look at you and others don’t seem to care."
Evolution of dolphins Dolphins sometimes ground themselves en masse on beaches and die like pilot whales. Scientist are not sure why they do this. They speculate that perhaps it is caused by disease or parasites. See Whales.
Dolphins sleep only two or three hours day. Dr. Sam Ridgeway of the U.S. Naval Ocean System center says "curiously, they seem to be able to sleep with one eye open, and with half the brain still awake." Often they don't sleep at all.. Sometimes when they rest one side of the brain sleeps while the other is awake. When the one side wakes up the other side sleeps.
One reason why they don’t sleep or sleep so little seems to be the need to be on the alert for predators. When they do sleep they either drifting on the surface, where they can breath, or take a lung full of oxygen and dive to the seabed and lay down there. open. Those that rest or sleep on near surface swim slowly and rise to the surface every minute or so to breath. Spinner dolphins go to specific areas to rest and relax during the day, presumably so they are ready for hunting at night. ⊗
Dolphin Social Behavior, Grief and Aggression
Dolphins are social animals that often travel in herds of 50 to 100 individuals. They spend a lot of time each day caressing one another. Sometimes they even rub up against boats in a friendly way. Some say their social behavior is similar to that of lions.
Mothers and their calves are the main components of large bottlenose dolphin social groups that often include three generations. These social groups are often part of large communities that include the roving males in a specific area. Males often pair off with unrelated males in early life and form bonds that last their entire lives. Theses males often surface and breath at the same time when swimming together.
Dolphins are said to feel sorrow. A Croatian newspaper reported that a dolphin appeared to beach itself near the southern Adriatic town of Ploce in an apparent suicide attempt after its offspring perished a few days before at the same spot. According to the newspaper fisherman found a dead baby striped dolphin, then a couple days later they observed an older striped dolphin trying to beach itself. Attempts to lead the dolphin back out to sea only resulted in the dolphin trying to beach itself again.
Dolphins enjoy roughhousing. Bottlenose dolphins often scrape each other with their teeth and occasionally inflict broken jaws. Dolphins are one of the few large animals that seems to kill for the fun of it and commit acts of infanticide. Off Scotland, a scientist once watched in horror as an adult dolphin picked up an infant dolphin in its mouth and beat it against the water repeatedly for an hour. Off Virginia, researchers found nine dead baby dolphins, with their skulls and ribs smashed and teeth marks matching those of adult dolphins.
Many dolphins bear scars from encounters with sharks. Sometimes sharks attack dolphins and sometimes dolphins attach sharks, but most of the time they ignore each other. Scientist have seen a pilot whale helping a sick Dall's porpoise.⊗
Feeding Dolphins
Dolphins off Oman Dolphins, porpoises and toothed whales generally grab prey with their toothy jaws and swallow it whole in their multi-chambered stomachs. Dolphins eat about 20 to 30 pounds of fish a day. They eat many mackerel, squids, blue fish and herring. These fish provide them with water as well protein, vitamins and calories..┵
Dolphins catch flying fish by jumping out of the water and stunning their prey with a head butt before eating it. Some dolphins chase schools of fish onto the shore and then climb up on land and eat them.┺
Bottlenose dolphins that live in waters off South Carolina form small groups of a half dozen or so that move inshore to fish in winding channels between sand bars and low flat islands. These dolphins have to make decisions about the tide, the presence of fish and other factors to determine the best places to feed. They often make snap judgments at a given moment and need to communicate and relay information back and forth between members.
Describing the South Carolina dolphins on the hunt, David Attenborough wrote: “At low tide, the falling water exposes narrow strips of mud between the water’s edge and the reed bed beyond. The dolphins swim back and forth in a rough semicircle from one end to another of such a mud-bank, moving closer and closer to it. Then, with perfect synchronization the suddenly come together to form a line abreast with their flanks almost touching, and charge towards the mud bank, driving shoals of small fish ahead of them. They swim so fast and with such power they create a bow wave that sweeps them and the fish right out of the river and up on the mud. As the water drains away, the dolphins roll over on their flanks and snap up the fish with the sides of their mouths. They all turn in the same direction — always on their left flank...Then the dolphins, flapping their bodies energetically, wriggle back into water and swim further up river to repeat the performance on another mud-bank.”
Pacific white-sided dolphins have been observed working as a team to attack schools of herring by coming at the school from all sides and pushing it near the surface into a tight mass and then plucking away at herring on the edge. If the school attempts to retreat the dolphins use bubbles and physical force to keep it a tight mass. Often seabirds show up to join in on the feast. Dolphins, seal lions and sharks have been seen together hunting stragglers from large schools of fish off South Africa.
Intelligent Dolphins
dolphin, human and rhinoceros brains Dolphins are one of the world's most intelligent animals. Only human's have a larger brain relative to their body size. A 300 pound dolphin has 1,700 gram brain, compared to a 150 pound man with a 1,500 gram brain. The dolphin brain has the same of layers a human brain has — six — and 50 percent more cortex cells than the human brain.┵
Dolphin think and speak very quickly and get bored by simple tasks,. They like challenging problems. Their attention span is so short they get often lose interest and get bored with slow-moving humans. Dolphins have a memory capacity equal to humans; they can follow complicated directions and remember long strings of random numbers. In marine park shows some dolphins reportedly remind their human trainers what to do if they forget part of their routine. ┺ ┵
Dolphins, along with apes and humans, are the only known species that are aware of their own images and recognize themselves in a mirror. Scientists measure this ability by making marks on a dolphin’s body with markers and sham marks in which the dolphins body was touched but no marks were made. The dolphins examined the marks in the mirror but didn't check the sham marks which scientist say indicates they are aware. Many other animals react to their images in a mirror as it were another animal.
Dolphins at Shark’s Bay Australia have been observed pushing around large pieces of sponge. It is believed they use them as a mask for protection again things like stingrays and sea anemones when they bottom feed. If this the case his is the first known use of tools among wild dolphins. The practice seems to have originated among one female who taught the trick to other females — which some anthropologists say makes it a form of culture, or at least a socially-learned technique. In the years after the behavior was first observed only one male was seen doing the trick.
Dolphin Games, Tests and Medicines
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In one set of laboratory tests dolphins have followed instructions and chosen the correct object from one that is virtually identical. In a different test a dolphin was given instructions and then relayed those instructions to another dolphin who was hidden behind a wall. Blindfolded dolphins can weave their way perfectly through a metal maze and trained dolphins understand statements like "get the surfboard."
Dolphins have been encouraged to tidy up their tank by offering them a mullet for every piece of trash they picked up. One time a dolphin ripped a brown paper bag into pieces so it could get more fish, and even hid a stash of trash so it could get more fish later. ⊗
Dolphins like to play twenty questions using a red ball for "yes" and a blue one for "no." They can answer questions like "Is it cylindrical?", distinguish between steel, brass and aluminum and recognize the difference between solid and hollow.
Dolphins have skin problems, uclers and get pneumonia. Nervous ones are sometimes given tranquilizers to calm them down. Ones with ulcers are treated with one gallon of ground-fish and Maalox broth three times a day. Dolphins can not be anesthetized because they lose their reflexes for breathing One time a dolphin swallowed an iron bolt and a six foot nine basketball player had to called in to reach down the dolphin's gullet and retrieve it.⊗ ┵
Dolphins Use Shells to Catch Fish
dusky dolphin In August 2011 Reuters reported, “Dolphins in one western Australian population have been observed holding a large conch shell in their beaks and using it to shake a fish into their mouths — and the behavior may be spreading. Researchers from Murdoch University in Perth were not quite sure what they were seeing when they first photographed the activity, in 2007, in which dolphins would shake conch shells at the surface of the ocean. [Source: Reuters, August 29, 2011]
"It's a fleeting glimpse — you look at it and think, that's kind of weird," said Simon Allen, a researcher at the university's Cetacean Research Unit. "Maybe they're playing, maybe they're socializing, maybe males are presenting a gift to a female or something like that, maybe the animals are actually eating the animal inside," he added.
But researchers were more intrigued when they studied the photos and found the back of a fish hanging out of the shell, realizing that the shaking drained the water out of the shells and caused the fish that was sheltering inside to fall into the dolphins' mouths.A search through records for dolphins in the eastern part of Shark Bay, a population that has been studied for nearly 30 years, found roughly half a dozen sightings of similar behavior over some two decades. Then researchers saw it at least seven times during the four-month research period starting this May, Allen said.
"There's a possibility here — and it's speculation at this stage — that this sort of change from seeing it six or seven times in 21 years to seeing it six or seven times in three months gives us that tantalizing possibility that it might be spreading before our very eyes," he added. "It's too early to say definitively yet, but we'll be watching very closely over the next couple of field seasons," Allen said.
Rough-toothed dolphin The Shark Bay dolphin population is already unusual for having developed two foraging techniques, one of which involves the dolphin briefly beaching itself to grab fish after driving them up onto the shore. The other is "sponging" — in which the dolphins break off a conical bit of sponge and fit it over their heads like a cap, shielding them as they forage for food on the sea floor. But both of these spread "vertically," mainly through the female dolphin population, from mother to daughter.
The intriguing thing about this new behavior with the conch shells is that it might be spreading "horizontally," Allen said. "If it spreads horizontally, then we would expect to see it more often and we'd expect to see it between 'friends'," he added, noting that dolphins are known for having preferences in terms of companions and whom they spend time with." Most of the sightings from this year are in the same habitat where we first saw it in 2007, and a couple of the individuals this year are known to associate with the ones that we saw doing it a year or two ago."
The next step would be not only to observe the behavior again in another season, but also to try and gather evidence Of deliberate actions on the part of the dolphins. "If we could put some shells in a row or put them facing down or something like that and then come back the next day, if we don't actually see them do it but find evidence that they've turned the shell over or make it into an appealing refuge for a fish, then that implies significant forward planning on the dolphins' parts," Allen said. "The nice idea is that there is this intriguing possibility that they might manipulate the object beforehand. Then that might change using the shell as just a convenient object into actual tool use," he added.
Dolphin Hearing, Noise Making and Echolocation
Dolphin head sound production All toothed whales and dolphins produce sound to communicate, navigate, and locate prey and have a melon, an oval fat-filled organ in their foreheads. A melon focuses outgoing sounds. It evolved from a sac off the main nasal passage for moving air back and forth to create sound vibrations. The lower jaw helps catch returning vibrations.
Dolphins whistle, grunt, squawk and make clicking noises. They make a variety of hissing noises like air escaping from a balloon by blowing air through nasal sacs inside their skull. Most sounds are made in the nasal passages not the larynx. Some believe the clicking noises are generated by forcing air from two sacks near the blowholes. Others believe they are formed by forcing nasal plugs against bony edges of the skull.
Dolphins “hear” using their jaws. They don’t have an outer ear. Instead, sound travels to the inner ear through a thin "window" in the lower jawbone. Clicks can be rattled off at a rate of up to 700 per second or generated as a drawn-out individual sound. The frequency of these clicks varies between 20 cycles per second and 170,000 cycles per second. The human ear can only detect sounds as high as 16,000 cycles per second. ┺┵
Dolphin click frequency Dolphins — like bats and many whales — use echolocation to locate objects. They make whistles, and ultra-sounds with frequencies of 200,000 vibrations a second with their larynx and produce clicks by forcing air through special passages and sinuses in the heads. The clicks and ultra-sounds pass through the melon, where the clicks are focused, and strike objects outside the dolphin and return to the dolphin brain like radar, enabling a dolphin to determine the distance and certain things about the objects. Blindfolded dolphins can detect a object three inches in diameter from a distance of a 120 meters.
Dolphins rely on echolocation more than sight to sense objects. Not only can they deduce the presence of an object with echolocation they can deduce its size and what it is. They can also determine if a container is full or empty and distinguish between a rock and a piece of flesh. Studies have shown that dolphins are almost as good at picking out objects of different shapes and sizes when they blindfolded as when they are not blindfolded.
Researchers have found that sonar may harm dolphins. In the spring of 2000, a dolphin beached itself and died on a beach on a northern Bahamas island, near where United States Navy ships were using powerful sonar (230 decibels, as loud as a rocket taking off) in anti-submarine exercises. A necropsy showed hemorrhaging around the brain and ear bones that may have caused them to beach themselves and may been caused by the impact of the sonar from the ships. See Whales.
Dolphins Communication
Dolphin click time Dolphins are among the most vocal animals. They communicate by using body language and at least 30 different sounds and vocalizations. Members of a group can communicate with one another of large expanse of open ocean. They can hear each over of at least half a mile. There are still a lot basic things about dolphin communication that scientists don’t understand: for example how they synchronize themselves when the leap in formation.
Dolphins use unique whistles to identify themselves and make sounds to express excitement and moods and exchange messages that help keep groups together and warn others of danger. Individual identity is practiced by humans and dolphins but few other members of the animal kingdom.
Dolphins appear to use body language and non-verbal communication. They touch, nudge and stroke one another in a way that seems to convey meaning. On biologist discovered that young Atlantic spotted dolphins let their mothers know everything is okay by pressing against their backs.
Studies in the Bahamas with wild dolphins indicates that dolphins change the meanings of sound by accompanying them with different postures. At a dolphin park in the Florida Keys a calf born to a deaf dolphin — who spoke in a monotone similar to that of deaf humans who can not speak — was given a “chat line” — consisting of underwater speakers and microphones connected to facilities with other young dolphins’so it could learn to speak normally.
Dolphin Identity Whistles
Dolphin family "Each dolphin has a distinctive signature whistle," says oceanographer Peter Tyack, "Infants tend to develop a whistle unlike those of their parents, and other dolphins learn to associate each whistle with the appropriate individual. By listening to whistles a dolphin can keep track of the other dolphins even when it cannot see them." The sounds of the whistles vary and serves a purpose similar to a human name. Each dolphin usually develops whistle made up of a pattern of rising and falling tones in its first year.
In a process called "whistle matching,” it seems that a dolphin can also call a particular individual by imitating its whistle. This is regarded as an important step in developing language. Tyack believes dolphins pass on other kinds information in similar ways. In addition to demonstrating their ability to communicate, he says, the whistles, and they way they are aquired and used, show dolphins are organized into an "educated society, one based on learning.” ┺
Scientists can call dolphins with a pinger. Dolphins can not imitate human sounds very well but they seem to respond to the number of syllables a dolphin males. If a scientist counts from one to six the dolphin responds with six noises.┵
Dolphins and Language
Dolphins perform certain behaviors in correspondence to certain sounds. Some dolphins respond to "sentences" such the command "surfboard-right-Frisbee-fetch" in which the dolphin chose a Frisbee on the right and places it on a floating surfboard. Some say this constitutes a kind of language but others say it doesn’t. The naysayers insist there is no proof that dolphins use grammar, syntax or are able to construct even two-word sentences.
Bottlenose dolphin mother and juvenile Louis Herman of the Kewalo Basin Marine Mammal Laboratory in Hawaii developed sign, hand and arm language, complete with grammar, to communicate with dolphins, including one named Akeakamai. Virginia Morrel wrote in National Geographic, “For instance, a pumping motion of closed fists meant “hoop” and both arms extended overhead (as in jumping jacks) meant “ball.” A “come here” gesture and a single arm told them to “fetch.” Responding to the request “hoop, ball, fetch,” Akeakamai would push the ball to the hoop. But if the word order was changed to “ball, hoop, fetch,” she would have to carry the hoop to the ball.”
Over time Akeakamai could interpret more grammatically complex requests, such as “right basket, left Frisbee” in which she would put a Frisbee on her left in the basket on her right. Morrel wrote: “Reversing “left” and “right” in the instructions would reverse Akeakamai’s actions, Akeakamai could complete such requests the first time they were made, showing a deep understanding of the grammar of the language.” Dolphin “readily imitated motor behaviors of their instructors too. If a trainer bent forward and lifted a leg, the dolphin would turn on its back and lift its tail in the air.” Imitation used be regarded as a simple activity but cognitive scientists now regard it as a complex behavior that requires recognition of the self.
Herman told National Geographic, Dolphins “are a very vocal species, Our studies showed that they could imitate arbitrary sounds that we broadcast into their tank, an ability that may be tied to their own need to communicate, “I’m not saying they have a dolphin language. But they are capable of understanding the novel instructions that we converse to them in a nurtured language; their brains have that ability...There are many things they could do that people have always doubted about animals. For example, they correctly interpreted, on the very first occasion gesture instructions given by a person displayed on a TV screen behind an underwater window. They recognized that television images were representations of the real world that could be acted on in the way as the real world.”
Dolphin Sex
Dolphin fetus Dolphins are horny creatures. They often seen mating and engaging in other sexual activities. Maybe that is the real reason they have such big smiles. In Britain a swimmer was once accused of molesting a dolphin. But later biologist explained that male dolphins often rub their penis against other dolphins as a greeting.
Dolphins usually mate to produce calves in the spring, with females often linking up with a roving male. Adult males often enter the territories of other males to make mischief and mate with new females. According to one study about 30 percent of calves are fathered by males that are not part of the community.
Males sometimes appear to gang rape females. Describing one pair of males around a female dolphin researcher Ester Quintana told Discover, "One was under the female and the other was trying to mount her — like a sandwich. They tried for 20 minutes." She doesn't think it was an isolated case. "We see pairs of males isolating a female from the group and flanking her, a male on each side. Sometimes they flank her for hours to a week.”
Dolphins have a very irregular ovulations cycle. Using ultrasound technology scientist at aquariums have been able to predict ovulation and produce dolphin offspring through artificial insemination. Females can reproduce for a long time. The oldest known reproducing female was still making babies at the age of 49.
Dolphin Young
Bottlenose dolphin with young After a gestation period of one year a three-foot-long calf is born tail first. If it was born headfirst it might drown. After the calf is born the mother darts away quickly to break the umbilical chord and allow the calf to swim to surface for is first breaths of air. Swimming by the mother is a "midwife" female who helps the calf to the surface for its first breath and then sticks with the mother for several weeks to help protect the calf and babysits when the mother fetches food.┵
Mothers apparently need some time to develop their mothering skills. According to one study 85 percent of first born dolphins only survive until adulthood. Offspring born later have a better chance of survival.
Dolphin young may nurse from their mother for several years. The female has a special set of muscles near her milk-producing glands. When her calf nuzzles the female squirts milk into the baby's mouth. The squirt only last for a few seconds to give the calve time to rise to the surface for air. The process is repeated several times until the calf is full.┵
common dolphin Young dolphins usually begin eating fish at about the age of six months, sometimes taking large prey and hitting it against the sea floor or smacking it on the ocean surface to break it into small easy-to-digest pieces. Young dolphins also catch and release their prey, apparently for the fun for it and to improve their hunting skills.
Calves don’t sleep their first month of life. After that they sleep only for short periods of time. Their mothers too get little sleep because they are almost constantly tending or watching over their young. It is believed that prolonged wakefulness by the mother: 1) protects the newborn from predators; 2) ensures the calf doesn’t drown while sleeping; and 3) keeps the calf warm until it has amassed enough blubber to warm itself.
Young dolphins play by chasing one another through the water. Adolescent dolphins of both sexes join juvenile groups that goof around, have sex and act rowdy like human teenagers. When females become pregnant they join a group made up of female-calf pairs.
Image Sources: 1) Wikimedia Commons; 2) NOAA; 3) Mikurashima tourism
Text Sources: Mostly National Geographic articles. Also the New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Natural History magazine, Discover magazine, Times of London, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.
Last updated March 2011