Common dolphin
Encyclopedia
The common dolphin is the name given to two species (and possibly a third) of dolphin
making up the genus
Delphinus.
Prior to the mid-1990s, most taxonomists
only recognised one species in this genus, the common dolphin Delphinus delphis. Modern cetologists usually recognise two species - the Short-beaked common dolphin
, which retains the systematic name Delphinus delphis, and the long-beaked common dolphin
Delphinus capensis. Some studies suggest that a third species, the Arabian common dolphin (D. tropicalis), can be characterized by an extremely long and thin beak and found in the Red Sea
and Indian Ocean
.
The common dolphin is not the dolphin of popular imagination despite its name; that distinction belongs to the bottlenose dolphin
due to its widespread use in marine parks and its appearance in the television series Flipper
. However, this dolphin was the most frequently represented in the art and literature of ancient Greece and Rome.
pattern colored light grey, yellow or gold in front and dirty grey in back. They have long, thin rostrums with up to 50–60 small, sharp, interlocking teeth on each side of each jaw.
Despite the historic practice of lumping the entire Delphinus genus into a single species, these widely distributed dolphins exhibit a wide variety of size, shape and colour. Indeed over the past few decades over 20 distinct species in the genus have been proposed. Scientists in California in the 1960s concluded that there were two species - the long-beaked and short-beaked. This analysis was essentially confirmed by a more in-depth genetic study in the 1990s. This study also suggested that a third species (D. tropicalis, common name usually Arabian common dolphin), characterized by an extremely long and thin beak and found in the Red Sea and Indian Ocean, might be distinguished from the long-beaked species. The current standard taxonomic works recognize this as just a regional variety.
s and escarpment
s. Common dolphin have a varied diet consisting of many species of fish and squid. This includes mesopelagic
fish and squids found in the deep scattering layer They also eat epipelagic schooling species such as scombroids, elupeoids and market squids. They have been recorded to make dives up to 200 metres (656.2 ft) deep.
Common dolphins can live in aggregations of hundreds or even thousands of dolphins. They sometimes associate with other dolphin species, such as pilot whale
s. They have also been observed bow riding on baleen whale
s, and they also bow ride on boats. It is a fast swimmer (up to 60 km/h), and breaching behavior and aerial acrobatics are common with this species.
The Short-beaked common dolphin has a gestation period
of 10 to 11 months. The newborn calf has a length of between 70 and 100 cm (2.3 and 3.3 ft) and weights about 10 kilograms (22 lb). For the Black Sea
population, weaning
occurs at between 5 and 6 months, but occurs later (up to about 19 months) in other areas. Typical interbirth interval ranges from 1 year for the Black Sea population to 3 years for eastern Pacific Ocean
populations. Age of sexual maturity also varies by location, but can range between 2 and 7 years for females and 3 and 12 years for males. There is no evidence of any major reproductive differences between the two species. In captivity, the long-beaked common dolphin has hybridized with the common bottlenose dolphin
(Tursiops truncatus). One of the hybrids has been bred back to a bottlenose dolphin, demonstrating that such hybrids are fertile.
for use as food and shark
bait. In most other areas the dolphins have not been hunted directly. Several thousand individuals have been caught in industrial trawler nets throughout their range. Common dolphins were abundant in the western Mediterranean Sea until the 1960s but occurrences there have tailed off rapidly. The reasons are not well understood but are believed to be due to extensive human activity in the area. In the U.S. they are a protected species and sometimes are caught by accident in some trawler nets as bycatch, though despite this they are still quite common throughout their range. Despite these potential threats, the short-beaked common dolphin is considered to be Least Concern by the IUCN Red List, and the long-beaked common dolphin is listed as Data Deficient.
The short-beaked common dolphin Delphinus delphis is listed globally on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS) as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements. The Mediterranean population of the short-beaked common dolphin is also listed on Appendix I, as this population has been categorized as being in danger of extinction throughout all or a significant proportion of their range and CMS Parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them. In addition, the species is also covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS
) and the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS
). They are cute pets and they are great at swimming
, San Diego but deemed unfit to release back to the ocean. These common dolphins remained at SeaWorld with the bottlenose dolphin exhibit. On one occasion a male common dolphin managed to impregnate one of the female bottlenose dolphins in the exhibit, leading to four hybrid births. One of the resulting common dolphin/bottlenose dolphin hybrids remained at SeaWorld, San Diego (alternately under the name Cindy or Bullet) while the other was kept at Discovery Cove
. They also participate in shows with bottlenose dolphin and pilot whale at Sea World.
Other than at SeaWorld, at least 90 common dolphins are known to have been captured from the wild and kept in captivity. Captured common dolphins are said to be difficult to keep in captivity.
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
making up the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Delphinus.
Prior to the mid-1990s, most taxonomists
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
only recognised one species in this genus, the common dolphin Delphinus delphis. Modern cetologists usually recognise two species - the Short-beaked common dolphin
Short-beaked Common Dolphin
The short-beaked common dolphin is a species of common dolphin. It has a larger range than the long-beaked common dolphin , occurring throughout warm-temperate and tropical oceans, with the possible exception of the Indian Ocean...
, which retains the systematic name Delphinus delphis, and the long-beaked common dolphin
Long-beaked Common Dolphin
The Long-beaked Common Dolphin is a species of common dolphin. It has a more restricted range than the Short-beaked Common Dolphin . It has a disjointed range in coastal areas in tropical and warmer temperate oceans...
Delphinus capensis. Some studies suggest that a third species, the Arabian common dolphin (D. tropicalis), can be characterized by an extremely long and thin beak and found in the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
and Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
.
The common dolphin is not the dolphin of popular imagination despite its name; that distinction belongs to the bottlenose dolphin
Bottlenose Dolphin
Bottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
due to its widespread use in marine parks and its appearance in the television series Flipper
Flipper (1964 TV series)
Flipper, from Ivan Tors Films in association with Metro-Goldwyn-Mayer Television, is an American television program first broadcast on NBC from September 19, 1964, until April 15, 1967. Flipper, a bottlenose dolphin, is the companion animal of Porter Ricks, Chief Warden at fictional Coral Key Park...
. However, this dolphin was the most frequently represented in the art and literature of ancient Greece and Rome.
Physical characteristics
Both common dolphin species are medium sized dolphins. Adults range between 1.9 and 2.5 m (6.2 and 8.2 ft), long, and can weigh between 80 and 235 kg (176.4 and 518.1 lb), although a range between 80 and 150 kg (176.4 and 330.7 lb) is more common. Males are generally longer and heavier. The color pattern on the body is unusual. The back is dark and the belly is white, while on each side is an hourglassHourglass
An hourglass measures the passage of a few minutes or an hour of time. It has two connected vertical glass bulbs allowing a regulated trickle of material from the top to the bottom. Once the top bulb is empty, it can be inverted to begin timing again. The name hourglass comes from historically...
pattern colored light grey, yellow or gold in front and dirty grey in back. They have long, thin rostrums with up to 50–60 small, sharp, interlocking teeth on each side of each jaw.
Differentiating species
Natural history
Common dolphins live in both warm-temperate and tropical waters worldwide between 40-60°N to 50°S. Long-beaked common dolphins prefer shallower and warmer water closer to the coast. Short-beaked common dolphins are common along shelf edges and in areas with sharp bottom relief such as seamountSeamount
A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface , and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of depth. They are defined by oceanographers as...
s and escarpment
Escarpment
An escarpment is a steep slope or long cliff that occurs from erosion or faulting and separates two relatively level areas of differing elevations.-Description and variants:...
s. Common dolphin have a varied diet consisting of many species of fish and squid. This includes mesopelagic
Mesopelagic
The mesopelagic is that part of the pelagic zone that extends from a depth of 200 to 1000 metres below the ocean surface. It lies between the photic epipelagic above and the aphotic bathypelagic below, where there is no light at all...
fish and squids found in the deep scattering layer They also eat epipelagic schooling species such as scombroids, elupeoids and market squids. They have been recorded to make dives up to 200 metres (656.2 ft) deep.
Common dolphins can live in aggregations of hundreds or even thousands of dolphins. They sometimes associate with other dolphin species, such as pilot whale
Pilot whale
Pilot whales are cetaceans belonging to the genus Globicephala. There are two extant species, the long-finned pilot whale and the short-finned pilot whale . The two are not readily distinguished at sea and analysis of the skulls is the best way to tell the difference between them...
s. They have also been observed bow riding on baleen whale
Baleen whale
The Baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...
s, and they also bow ride on boats. It is a fast swimmer (up to 60 km/h), and breaching behavior and aerial acrobatics are common with this species.
The Short-beaked common dolphin has a gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
of 10 to 11 months. The newborn calf has a length of between 70 and 100 cm (2.3 and 3.3 ft) and weights about 10 kilograms (22 lb). For the Black Sea
Black Sea
The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...
population, weaning
Weaning
Weaning is the process of gradually introducing a mammal infant, either human or animal, to what will be its adult diet and withdrawing the supply of its mother's milk.The process takes place only in mammals, as only mammals produce milk...
occurs at between 5 and 6 months, but occurs later (up to about 19 months) in other areas. Typical interbirth interval ranges from 1 year for the Black Sea population to 3 years for eastern Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
populations. Age of sexual maturity also varies by location, but can range between 2 and 7 years for females and 3 and 12 years for males. There is no evidence of any major reproductive differences between the two species. In captivity, the long-beaked common dolphin has hybridized with the common bottlenose dolphin
Common Bottlenose Dolphin
Tursiops truncatus, commonly known as the Common Bottlenose Dolphin, is the most well-known species from the family Delphinidae.Common bottlenose dolphins are the most familiar dolphins due to the wide exposure they receive in captivity in marine parks, dolphinarias, in movies, and television...
(Tursiops truncatus). One of the hybrids has been bred back to a bottlenose dolphin, demonstrating that such hybrids are fertile.
Conservation
Common dolphins face a mixture of threats due to human influence. Moderate levels of metal pollutants, which are thought to negatively impact dolphin health, have been measured in some populations. Populations have been hunted off the coast of PeruPeru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
for use as food and shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
bait. In most other areas the dolphins have not been hunted directly. Several thousand individuals have been caught in industrial trawler nets throughout their range. Common dolphins were abundant in the western Mediterranean Sea until the 1960s but occurrences there have tailed off rapidly. The reasons are not well understood but are believed to be due to extensive human activity in the area. In the U.S. they are a protected species and sometimes are caught by accident in some trawler nets as bycatch, though despite this they are still quite common throughout their range. Despite these potential threats, the short-beaked common dolphin is considered to be Least Concern by the IUCN Red List, and the long-beaked common dolphin is listed as Data Deficient.
The short-beaked common dolphin Delphinus delphis is listed globally on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS) as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements. The Mediterranean population of the short-beaked common dolphin is also listed on Appendix I, as this population has been categorized as being in danger of extinction throughout all or a significant proportion of their range and CMS Parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them. In addition, the species is also covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS
ASCOBANS
ASCOBANS is a regional agreement on the protection of small cetaceans that was concluded as the “Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas” under the auspices of the UNEP Convention on Migratory Species, or Bonn Convention, in September 1991 and came into force...
) and the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS
ACCOBAMS
ACCOBAMS, the Agreement on the Conservation of Cetaceans in the Black Sea,Mediterranean Sea and contiguous Atlantic area is ‘a cooperative tool for the conservation of marine biodiversity in the Mediterranean and Black Seas’....
). They are cute pets and they are great at swimming
Captivity
Common dolphins are not common in captivity. But on at least three occasions, a beached common dolphin in California was nursed back to health at SeaWorldSeaWorld
SeaWorld is a United States chain of marine mammal parks, oceanariums, and animal theme parks owned by SeaWorld Parks & Entertainment. The parks feature captive orca, sea lion, and dolphin shows and zoological displays featuring various other marine animals. There are operations in Orlando,...
, San Diego but deemed unfit to release back to the ocean. These common dolphins remained at SeaWorld with the bottlenose dolphin exhibit. On one occasion a male common dolphin managed to impregnate one of the female bottlenose dolphins in the exhibit, leading to four hybrid births. One of the resulting common dolphin/bottlenose dolphin hybrids remained at SeaWorld, San Diego (alternately under the name Cindy or Bullet) while the other was kept at Discovery Cove
Discovery Cove
Discovery Cove is a theme park in Greater Orlando, Florida. Guests can interact with a variety of marine animals, most notably bottlenose dolphins. The park is located adjacent to sister parks SeaWorld Orlando and Aquatica. In addition to swimming with dolphins, Discovery Cove guests can interact...
. They also participate in shows with bottlenose dolphin and pilot whale at Sea World.
Other than at SeaWorld, at least 90 common dolphins are known to have been captured from the wild and kept in captivity. Captured common dolphins are said to be difficult to keep in captivity.
Further reading
- Heptner, V. G.; Nasimovich, A. A; Bannikov, Andrei Grigorevich; Hoffmann, Robert S, Mammals of the Soviet Union, Volume II, part 3 (1996). Washington, D.C. : Smithsonian Institution Libraries and National Science Foundation
External links
- Whale and Dolphin Conservation Society
- An earthOCEAN documentary film about common dolphin decline in the eastern Mediterranean Sea
- Convention on Migratory Species page on the Short-beaked common dolphin
- Official website of the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area
- Official website of the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas