Our Dolphin Friends and Their Distinctive Features
written by: ciel s cantoria•edited by: Donna Cosmato•updated: 11/29/2010
Discover several interesting facts about these fascinating creatures, so you can be aware of how human activities could cruelly impact their existence.
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General Dolphin Traits
Dolphins, along with whales and porpoises, belong to the mammalian order of marine animals known as cetaceans.
As a cetacean, the dolphin family is known as Delphinidae. Most, but not all, have distinct beaks called rostrums. They have a set of cone-shaped teeth, and their bodies are covered with thick, hairless and glandless skin, which is kept smooth by the constant sloughing-off of the outermost skin layers.
Dolphins are carnivores; they feed on fish and other invertebrates like cuttlefish, squids, octopus, crabs, shrimp, and lobsters.
Each type of dolphin has to find its habitat according to an ecosystem by which its characteristics fit.
The speed at which dolphins swim with the aid of their flippers and powerful tails depends on their habitats and prey. The coastal types move at about 10 miles per hour (mph), while the oceanic kind have the ability to move as fast as 15 to 25 mph.
Dolphins travel not just by swimming alone, but also through leaps and bounds; some of them spin while diving in and out of the water.
Others have been observed riding the bow waves of fast-moving sea vessels as their way of gaining speed.
A dolphin-calf is born with its tail part coming out first, while its eyes are already wide open and alert. This is necessary for the calf’s survival because it has to follow its mother immediately on the way up to the surface in order to catch its very first breath of air.
Although some suggest the dolphin’s level of intelligence is comparable to that of the regular human, other marine scholars caution that this should not be taken as a generality among dolphins. Its habitat and environment are influential factors to a dolphin’s mental capabilities, and most of their survival skills were developed and adapted according to their home waters.
Dolphins emit clicking sounds through their blowholes, which tend to echo or resonate. The resonating sounds often catch-up with the succeeding clicking hums and thus produce a distinctive sound. Marine scientists call this behavior, echolocation, in which the sound waves bounce back from the waters to the dolphin’s ears. Their ears send messages to their brains, which create an acoustic vision that enables the dolphin to estimate the time and distance needed to reach their target. For more details about echolocation among these mammals, refer to “Hearing Your Way Around: Echolocations in Whales and Dolphins.
The Delphinadae are known to be very sociable and have been observed to form long-lasting bonds with their fellow dolphins. A small group of delphinids, called pod, can have from two to up to forty members. The large groups, on the other hand, are called schools or herds, comprising several hundreds up to thousands of different types of dolphin species in a single group.
At this point, we discuss the features which make one type of dolphin different from the others. The following sections provide a cursory view of these distinctions, and examine each type's current conditions in our present-day environment:
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The Different Types of Dolphins
1. The Bottlenose Dolphin
Take note of this delphinid’s image on your left, and notice how its stubby beak closely resembles a bottle’s neck; hence, earning for itself the moniker bottlenose. This species’ vertebral-structure is different from the other oceanic dolphins, as five out of its seven vertebrae are not hinged together, thus making the dolphin’s neck more flexible.
Although described and called white-beaked, the color of its rostrum borders more on grey. The white part is located in the belly area and on both sides of its flanks. This type of dolphin is found in the sub-arctic parts of the ocean; mostly, in the North Atlantic, off the Norwegian coasts, in the Baltic Seas, and occasionally along the Spanish coasts.
Observers have noted a marked decrease in the overall population of the white-beaked dolphins as hunters and fishermen in Newfoundland, Labrador, Greenland, and the Faeron Islands hunt and kill them, albeit not for commercial purposes. However, a corresponding increase in their population was noted in the European region, which could be interpreted as a migratory move by this species.
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This page of our article about the different types of dolphins contains brief descriptions of Pilot Whales, Risso's, Spotted, Orcas, Hourglass and Heaviside Dolphins. Read overviews on how each species' population is affected by pollution and degradation problems as well as human activities that prey on them for human consumption and commercial purposes.
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The Different Types of Dolphins (continuation)
3. The Short-Finned Pilot Whale
The features of this short-finned delphinid are somewhat whale-like for its lack of beak, the presence of a prominent bulge on its forehead and its rounded head. Their teeth are noticeably larger than those of the other dolphin species and are framed by a distinctively oblique mouth.
They are commonly found in tropical offshores or where the water temperature is relatively warmer; hence, a large number of them can be found in the Gulf of Mexico. A pilot-whale dolphin's pod is considered a noisy lot because the members make plenty of squealing, smacking, whistling, whining, and snoring sounds. Nonetheless, scholars distinguish this species as highly communicative.
Although mass-stranding may occur during severe storms, this dolphin species manages to survive by taking shelter along the in-shores. Currently, their population remains steady in numbers.
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4. Risso’s Dolphin
Risso’s dolphins are recognizable by their heavily-scarred bodies and by their blunt and almost square-shaped heads. However, from a distance, they could be mistaken for killer-whales because of their size and tall dorsal fins.
This species of Delphinadae are scattered across the western Atlantic, in Newfoundland, and along the Canadian and American east coasts. Their large numbers inhabit other parts of the globe including the Indian Ocean, from along the African coasts to the Bay of Bengal, through Indonesia and Sri Lanka.
Risso’s dolphins are known to interrelate with other cetaceans, particularly with the bottlenose herds. Although there are records showing cross breeds of dolphin species, their hybrids are feared to have been taken in captivity. Currently, the population of Risso’s dolphins remains relatively regular in numbers.
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5. Pantropical Spotted Dolphins
These are small dolphins with black rings around their eyes and a short black beak with a black stripe across the base. The whiteness of its abdomen makes the black spots very noticeable. In contrast, its black upper body parts are peppered with white spots.
These types of dolphins are prevalent in tropical and subtropical waters and are found abundantly in the Pacific, where they are frequently victimized by tuna-seining sea vessels. However, the mortality rates subsequently decreased as the territorial governments strictly implemented laws and programs that aim to lower the numbers to less than 5,000 dolphin lives lost annually.
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6. Long-Finned Pilot Dolphins
These dolphins inhabit the in-shores and bays of North Carolina during the summer but are largely predominant in Iceland’s and Greenland’s offshore waters. Owing to their large and bulbous melon-shaped body, they are often mistaken for whales, but they are definitely different because of their exceptionally long flippers. A grayish white stripe diagonally appearing behind their eyes adds to their distinctive features.
Due to their similarity to whales, they are affected by the whaling activities in the Nordic areas.
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7. Orca or Killer Whales
Some readers may be surprised to know that the Orcas, or killer whales, are actually dolphins. Their large, paddle-like flippers and the white patch around their eyes are the identifying marks that distinguish them from among other species. To learn more about these killer whales, read “Interesting Facts about the Orca Whales".
This delphinid has an hourglass silhouette pattern on its flanks; hence the hourglass name. In addition, they inhabit only the Southern Hemisphere and are found largely in Antarctica. Nonetheless, they can migrate as far as Australia, New Zealand, and South America.
Hourglass dolphins are the least of the species to encounter any threats because they prefer to stay in-shore most of the time.
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9. The Heaviside Dolphin
This dolphin species is often mistaken for a porpoise because of its small and robust body and lack of beak. However, the remarkable lines that separate into a fork-like pattern on its belly and the grayish black cape over its head serve as their identification as a Heaviside delphinid.
These dolphins prefer to inhabit the cold, shallower parts of the waters of the Benguela Current and hardly stray away from it or even migrate. However, researchers find it difficult to track or monitor their population or any possibility of endangerment, since there is not enough data provided by South Africa, Angola, and Namibia where large numbers of Heaviside dolphins exist.
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Page three of the examination of different types of dolphins contains brief descriptions of False & Pygmy Killer whales, Commerson's, Striped, Peale's, Melon-Headed, Irrawaddy, Frasier's and Hector's Dolphins. Learn about their distinctive features and their current status in today's environmental conditions.
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The Different Types of Dolphins (continuation)
10. False Killer Whale
Obviously, this dolphin earned its name due to its large resemblance to the Orca, but it could be easily identified by its mostly black color around the surface-visible parts of their bodies. The inner sections are of a lighter grayish-black shade.
It is generally believed that the false killer whales are near-extinct because only a few have been visible in recent years. The toxicity of the ocean’s contaminants and over fishing activities are considered the causes of its disappearance.
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11. Commerson’s Dolphin
The Commerson’s dolphin is a sociable and outgoing delphinid species, and it prefers to frolic in the coastal waters of the Falkland Islands, Tierra del Fuego, and the Straits of Magellan. Typically black with white Piebald-like patterns, this dolphin is characterized by a blazing white forelock sweeping through its midsection. Its wide and rounded dorsal fin is another identifying mark.
They can migrate as far as Chile and Argentina but are threatened by poachers who purposely kill them for their meat, which is used as crab bait.
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12. Striped Dolphins
These delphinadae are easily recognizable by the stripe that begins from their beaks running down through their flanks. They largely inhabit the major bodies of water, particularly the Atlantic and the Pacific Oceans and the Mediterranean seas. These marine creatures are well-loved for their acrobatic nature; they playfully flip, spin, leap, and plunge into the water in an upside down position.
There are no known threats against their population’s existence.
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13. Peale’s Dolphin
The main distinguishing marks of this dolphin species are the double black rings around its eyes extending toward the rostrum. This dolphin is a bow wave-rider, and an acrobat often observed in the company of Risso’s and Commerson’s dolphins in the Straits of Magellan. However, they prefer to nest in the cool open coastlines.
They are also threatened by poachers around Tierra del Fuego, who kill them for their meat. Overfishing of crabs in the areas resulted in the recent lack of zealousness in poaching activities.
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14. Pygmy Killer Whale
This dolphin is named by virtue of its character, since it has manifested aggressiveness and killer instincts by fatally attacking its fellow-dolphins. As an example, a pygmy killer whale in conservation killed a pilot whale which arrived to share the tank the pygmy was occupying. The cause of death was established as a sharp blow to the pilot whale's cranium with the use of the killer whale’s head.
Its main distinguishing features are the white lips and the white lower jaw, which resembles a goatee. Refer to illustration number one of this photo image. They can be found inhabiting the Gulf of Mexico, the Indian and Southeastern Atlantic Ocean, and around Sri Lanka and the Lesser Antilles.
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15. Melon Headed Whale
This species closely resembles the pygmy killer whale in size, shape, and color but a closer look at its face shows that it has a black widow’s peak-like mask on its face and none of the pygmy’s white goatee.
They inhabit mostly tropical and subtropical waters and are abundant in the Philippine Sea. There are no known reports of threats or endangerment to the population of the melon-headed whales.
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16. The Irrawaddy Dolphins
These delphinadae have the typical features of other dolphins, and their main distinctions as Irrawaddy species are their anatomical structures. They have no cardiac sphincter muscles, and their stomachs are divided into sections. They prefer to inhabit the coastal waters of Southeast Asia, Papua New Guinea, and Northern Australia.
The pods and herds inhabiting the Mekong River and Songkhla Lake are listed as critically endangered. Accordingly, they are affected not only by human activities like the constructions of dams and barges, which destroy their habitats, but also by the polluted waters in the area.
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17. Hector’s Dolphin
These dolphins are one of the smallest of all delphinid species and are found only in New Zealand’s waters. Conservation efforts for their preservation have proven successful, since there are no reports of threats and endangerments.
18. Frasier’s Dolphins
These types of delphinids are mostly grayish brown in color, and their identifying marks are the stripes on their backs and on their faces. There is not enough information about their distribution, but they have been frequently sighted around near-equator areas of the eastern Pacific. Reports are that they fall victim to the harpoons of Indo-Pacific poachers for both commercial and human consumption.
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Read about Dusky, Clymene, Chilean, Right whale, Round-Toothed, Short & Long Beaked Common Dolphins, on page four of this article about the different types of dolphins. Acquaint yourselves with their identifying marks as a way of distinguishing one species of dolphin from the others. Find out why some of these cetacean mammals have dwindled in numbers or cruelly impacted by human activities. .
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The Different types of Dolphins ( continuation)
19. Dusky Dolphins
These marine species have dark blue skin, and their main distinguishing mark is the dark diagonal band coming from the opposite flank, crossing diagonally, and extending up to the tail stock. They are agile and sociable creatures living together in large numbers in South America, the Indian Ocean, and New Zealand.
Largely, due to their active nature, the threats to their existence are the large fishing nets of trawlers plying the ocean waters. The mortality rates for gillnet entanglements range from 100 to 200 annually.
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20. Clymene Dolphins
Clymene dolphins are also called Senegal dolphins, or helmet dolphins, because of the dark line atop their short beaks, their dark lips, and the black rings around their eyes. Although occasionally spotted in New Jersey, they are more commonly found in the Gulf of Mexico, North America, the Caribbean, and West Africa.
Their existence in Lesser Antilles in the Caribbean waters is threatened by commercial hunters who use their meat as bait for sharks.
21. Chilean Dolphins
These dolphins are native to Chilean waters, and their color borders mostly on gray hues. They have white distinctive markings appearing on their foreheads, lips, throats, and at the backs of each flipper. A darker shade of gray instead of white covers their body; hence, they appear to be totally black.
Although considered illegal, the Chilean dolphins are still being slaughtered for their meat and used as bait for swordfish and crab fisheries. The lack of insufficient information about their population makes it difficult for researchers to establish the impact of the rampant illegal killings of these dolphins.
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22. Right Whale Dolphins
Included under this classification are the Northern Right Whale dolphins, which are the most gentle-looking of all delphinid creatures. Their slender bodies, lack of dorsal fins, small flippers, and tail flukes make them look less formidable than their other dolphin counterparts.
They are found mostly in the Pacific Ocean, and their existence is threatened by the fisheries operating in Japan, Korea, and Taiwan. An estimated 15,000 to 20,000 are taken-down each year, resulting in the depletion of their population at an estimated 73 percent.
23. Southern Right Whale Dolphins
Southern Right Whale dolphins found only in the cold waters of the Southern Hemisphere are luckier than their northern counterparts, because they are not as heavily hunted. Their only threats are the fishing nets during migration especially if they find themselves drifting along the Chilean and Peruvian coastlines.
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24. Rough-Toothed Dolphins
These delphinadae cetaceans have about twenty to twenty-seven teeth characterized by slight ridges in both the upper and lower jaws. If not for these sets of rough-edged teeth, they can easily be mistaken for a bottlenose, a spinner, or a spotted dolphin.
They are commonly found in the deep waters of the Pacific Ocean and Mediterranean Seas and all other tropical and sub tropical regions in between. Similar to all other dolphins inhabiting the eastern Pacific regions, they are threatened by the fisheries operating in the areas.
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25. The Short-Beaked Common Dolphin
This is the most common dolphin, which exists in all parts of the globe and whose features are considered classic or standard. Its body is sleek, long, and slender, and its beak is called short, only as a distinction to the long-beaked common dolphins. Their beak size, however, is comparatively larger than the other dolphin species.
They are abundant in almost all major bodies of water across the globe but generally stay along in-shore and coastal waters where the temperatures are moderately cool or warm. Aside from the threats of human activities in regions where whaling is rampant, they are also prey for sharks and killer whales.
26. The Long-Beaked Common Dolphin
The long-beaked common dolphin’s distinction to its short-beaked cousin is the pale yellowish band in its dark cape, which forms a crisscrossing hourglass pattern below its saddle area. Unlike their short-beaked counterparts, they are often found congregating with large groups of dolphins, whose average number of members ranges from 100 to 500, and which could reach to thousands.
They prefer the shallow warm waters of California’s coastal areas where their existence is protected from threats of slaughter and endangerment.
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The list of the different types of dolphins ends on this page, which completes our overviews about the interesting traits that differentiate the Pacific White-Sided, Spinner, Humpbacks, Atlantic and River Dolphins from all other species of delphinadae. Read on for more information about their physical distinctions and behaviors as well as the present status of their respective populations.
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The Different Types of Dolphins ( continuation)
27. Pacific White-Sided Dolphin
Some consider this dolphin species to have the most attractive features because their backs are well-defined as black, with white for the belly and light gray for the sides and accented by white stripes extending from the eyes to the tails. Their beaks and mouths are black and matched with dark rings that encircle their eyes.
Threats to their existence have diminished, as most of them have found suitable habitats in California’s coastlines, while those in the Pacific coasts are considered difficult to catch.
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28. The Long-Snouted Spinner Dolphin
This dolphin is cousin to the acrobatic Clymene dolphins, whose snouts are relatively longer than the latter. They are called spinner dolphins for their tremendous abilities to spin several times around on their axis in a longitudinal position, while completing a breaching motion. To learn more about spinner dolphins, Bright Hub’s related article entitled Species Spotlights: Spinner Dolphins, provides a comprehensive report.
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29. Indo-Pacific Humpback Dolphins
This species, also known as Chinese White dolphins, may be called humpback despite the not-so prominent hump on its back. The dolphin calves are born with dark colorings but turn lighter as they grow and age. They eventually attain pinkish hues of white yet retain some of the dark colorings as spots on their otherwise pinkish-white skin.
Their mortality rates are high in Africa and Eastern Australia as they are caught in anti-shark gillnets, while those inhabiting the Indian Ocean are slaughtered for blubber and human consumption. The degradation of mangroves contributes to the endangerment of those near coastal areas, as their food supplies become depleted.
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30. The Atlantic White-Sided Dolphins
The most distinctive features of this dolphin species are their prickly and pointed dorsal fins, aside from the yellowish patches on their dorsal sides. They are believed to be widely abundant and there are no known reports of wide-scale threats.
31. The Atlantic Hump-Backed Dolphin
Their distinction is not so much on their physical aspect but more on their seemingly high levels of intelligence. They have a high potential for understanding and communicating with humans and can adapt well to their habitats. In Mauritania, they found shelter near the shore to avoid the killer whales and while in this process, they established a working relationship with the local fishermen. They act as fish herders by bringing schools of fish nearer to the shore, to make fishing easier for the locals. Hence, their valuable services endeared them to the community.
32. Atlantic Spotted Dolphins
Physically, Atlantic Spotted dolphins have more spots than their pantropical counterparts. As they mature, more spots tend to appear on their skin. In fact, a species that is said to be heavily spotted with white may be mistaken for a white whale if viewed from afar. Generally, their population does not face any form of threat unless they enter the waters of the earlier-mentioned regions where poaching and whaling activities are rampant.
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33. The River Dolphins
The River dolphins are classified according to the regions in which they exist: the Yangtze River Dolphins, the Amazon River Dolphins, and the Ganges River Dolphins. The species found in the Amazon and Hindu areas are suffering from loss of biodiversity as rainforests and other natural resources have been degraded. The Chinese River dolphins are said to be functionally extinct, since they have been largely affected by the heavily polluted Yangtze River waters.
As a recap, these different types of dolphins find suitable habitats according to their feeding habits and swimming capabilities; hence, the loss of a particular ecosystem could spur them to migrate to other regions. Unfortunately, however, some species make the mistake of migrating to regions where poaching or whaling are rampant or where there are tuna and crab fisheries operating. These factors not only threaten their existence but could also lead to their species' extinction.
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Reference Materials and Image Credit Section
http://marinebio.org/search/ --- Marine Species Database
All images posted are courtesy of Wikimedia Commons.