Delphinus delphis

Short-beaked common dolphins hunt in groups of ten to ten thousand animals. They can reach speeds up to 45 kilometers per hour. They are also attracted to ships and like to play in their bow waves. Short-beaked common dolphins live in oceans; they aren't often seen swimming close to shore, usually preferring water no shallower than 200 meters. Nevertheless, they are occasionally seen in the Dutch section of the North Sea. Short-beaked common dolphins are the most common dolphin species in the region of the Mediterranean Sea. Pictures on ancient Greek vases show that it's been that way for centuries.

These fast-swimming dolphins are highly active (1), often leaping clear of the water (breaching), and slapping their flippers on the water surface (lobtailing) (3). They occur in large groups (3) of between 10 and 500 individuals (1), the size of group depending on both the time of day and year (3). The approach of these groups can be detected from miles away (1), and some noises made by this species can be heard from above the surface of the water (3). They feed on small fish and cephalopods such as squid (1), and are known to use co-operative methods of hunting (4). They make short dives typically of between 10 seconds and 2 minutes, but dives lasting for as long as 8 minutes have been recorded (3).

The short-beaked common dolphin is the commonest dolphin species (1), but exact numbers are unknown (3). It is easily identified owing to the obvious 'hourglass' pattern on the flanks, which creates a dark V-shape below the dorsal fin (1). Considerable variation in colours and patterns exists within this species (3), and in 1994 a new species, the long-beaked common dolphin was recognised, based on both anatomical and genetic differences (1).

Common dolphins can be found throughout the Atlantic and Pacific Oceans. They are abundant in the Mediterranean Sea, as well as in the Black Sea, the Gulf of Mexico, and the Red Sea. At times, these dolphins follow the Gulf Stream up to Norwegian waters. In addition, scattered populations have been found in the Indian Ocean and waters near Japan. They seldom venture into the Arctic.

(Baker, 1987;   http://whales.ot.com/).

Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )

circumglobal

East Pacific; Eastern Atlantic Ocean; Indo-West Pacific; Western Atlantic Ocean

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Transient

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Worldwide in subtropical and warm temperate oceans, including the Mediterranean Sea and Black Sea. In the Pacific Ocean, ranges from British Columbia south to Chile and out to 135 degrees west longitude; there are few records from the Gulf of California; documented from New Caledonia, New Zealand, and Japanese waters in the western Pacific, and there are records from north of Hawaii; range may extend entirely across the tropical and temperate North Pacific; records from the western Atlantic range from at least Florida to Newfoundland and in the eastern Atlantic from northern Europe to the west coast of Africa (Heyning and Perrin 1994). Abundant in waters of eastern North America, ranging north in large numbers to near Nova Scotia and Newfoundland in summer; otherwise, generally ranges from Gulf of Maine to Chesapeake Bay area (Gaskin 1992). Penetrates tropical zone where relatively cool waters keep surface temperature between about 15 to 26 C (Mead and Brownell, in Wilson and Reeder 1993, Gaskin 1992).

Occurs in all tropical, subtropical and warm temperate seas (5). Common, with a wide distribution in the eastern north Atlantic Ocean. Around the UK it is abundant in the western approaches to the English Channel, west of Ireland, in the southern Irish Sea and in the vicinity of the Inner Hebrides, reaching as far north as Skye (2).

The common dolphin is one of the smallest dolphins. Overall length can vary from 5 feet to a maximum of 8 feet. Females are slightly smaller than males. The common dolphin has a dorsal fin that is almost triangular, in addition to small flippers and flukes. The beak is sharply divided from the lower forehead by a deep groove. The beak is elongated and pointed more than any other species of the same genus. The jaws on each side of the beak are lined with 20 or more small, sharp, recurved teeth, perfect for catching slippery fish. Common dolphins are a colorful dolphin species. The back is either black or dark brown, and they have a white or cream-colored underside. A dark streak stretches from the the lower jaw to the flipper. The flippers and flukes are the same color as the back, black or dark brown, and the eyes are encirled with black markings that extend to the beak. The most distinctive feature is a crisscross pattern which runs across the dolphin's side. It resembles an hourglass and divides the top and bottom colors. This band is a buffy tan in front and gray towards the tail. This characteristic has given this species the nickname "crisscross dolphin".

(Allen, 1979; Baker, 1987; Flower, 1866).

Range mass: 100 to 136 kg.

Length: 2600 cm

Common dolphins are fond of coastal waters, but are also found well out to sea. Generally, they prefer surface temperatures greater than 10 degrees Celsius. These dolphins normally travel at 5 to 7 miles per hour (although they are known to reach speeds of 29 miles per hour when pursuing food), and can move up to 150 to 200 miles in a 48 hour period. When swimming, schools follow and dive over prominent features of the ocean bottom. Also, herd movements correlate with the seasonal shifts in population of certain fish.

(Alpers, 1961; Baker, 1987; Schevill, 1974;   http://whales.ot.com/).

Aquatic Biomes: benthic ; reef ; coastal

mainly offshore

oceanic, tropical to temperate

Depth range based on 6965 specimens in 1 taxon.
Water temperature and chemistry ranges based on 4409 samples.

Environmental ranges
  Depth range (m): 0 - 2150
  Temperature range (°C): 2.217 - 29.261
  Nitrate (umol/L): 0.000 - 17.224
  Salinity (PPS): 30.701 - 39.945
  Oxygen (ml/l): 4.117 - 7.897
  Phosphate (umol/l): 0.033 - 1.095
  Silicate (umol/l): 0.494 - 12.030

Graphical representation

Depth range (m): 0 - 2150

Temperature range (°C): 2.217 - 29.261

Nitrate (umol/L): 0.000 - 17.224

Salinity (PPS): 30.701 - 39.945

Oxygen (ml/l): 4.117 - 7.897

Phosphate (umol/l): 0.033 - 1.095

Silicate (umol/l): 0.494 - 12.030
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Habitat Type: Marine

Comments: Primarily pelagic, in waters of about 10-28 C; usually along or seaward of the 100 fathom contour. Young are born in the water.

Prefers waters that have a surface temperature higher than 10°C (4). It is less commonly seen in water shallower than 180m (6).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Delphinus delphis feed on small fish as well as squid and octopus. Small fish include young herring, pilchard, anchovies, nocturnal hake, sardines, small bonito, as well as sauries. Individual dolphins eat up to 18 to 20 pounds of fish per day. Groups of common dolphins all feed at the same time during the night or day. They are sometimes joined by bands of bottlenose or white-sided dolphins. These feeding forays can last up to an hour. During these, each dolphin rushes to the center of the school the group has been pursuing and tries to seize as many fish as possible, which it swallows whole. Common dolphins have also been known to dive below schools and drive them to the surface. They push their prey completely out of the water and catch them in midair.

(Allen, 1979; Alpers, 1961; Baker, 1987;   http://whales.ot.com/).

Animal Foods: fish; mollusks

Primary Diet: carnivore (Piscivore )

Comments: Feeds opportunistically on pelagic schooling fishes (e.g., smelt, herring, mackerel, mullet, lantern fish) and squid.

10,000 to >1,000,000 individuals

Comments: In the eastern tropical Pacific, northern stock population was estimated at around 500,000 in the 1980s; central stock evidently declined from around 500,000 in the late 1970s to about 250,000 in the 1980s; though data are weak, southern stock may have declined from 750,000 in 1976 to under 250,000 in 1982 (reanalysis yielded estimates that were a couple 100,000s lower) (see IUCN 1991). See IUCN (1991) for population estimates and trend information for other parts of the range (most data are difficult to interpret).

Travels in groups of a few to several thousand; commonly in groups of several hundred in the Pacific.

Comments: Active day and night.

Average lifespan
Status: wild: 20.0 years.

Common dolphins are viviparous, as are all mammals except monotremes. Females normally give birth to one baby at a time, but have been found to carry twins or triplets. Gestation usually lasts 10 to 12 months. When the calf is born (tail first) it is 3 feet long and usually weighs 25 to 35 pounds.

Common dolphins reach sexual maturity after 12 to 15 years. Courtship occurs in the spring and fall. Males and females court by stroking each other with their flippers, by vigorously rubbing their bodies together, and by swimming along side each other. The male often rushes towards the female as if he is about to bump into her before moving away. The female often swims away from the male's pursuits. After this playful courtship, these dolphins mate in the belly-to-belly position. The male enters the female with his hidden penis and gives a short series of pelvic thrusts. Females have also been observed thrusting. Other sexual activity includes beak-genital propulsion.

Common dolphins have an estimated life span of 35 to 40 years.

(Alpers, 1961; Baker, 1979; Cousteau, 1988; McIntyre, 1974;   http://whales.ot.com/).

Range number of offspring: 1 to 3.

Range gestation period: 10 to 12 months.

Range age at sexual or reproductive maturity (female): 12 to 15 years.

Range age at sexual or reproductive maturity (male): 12 to 15 years.

Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Average birth mass: 7000 g.

Average number of offspring: 1.

Babies immediately become a part of the family group. The calf stays close to its mother and never wanders more than a few feet away. The calf feeds on milk from the teats of its mother. Unlike human babies, however, dolphins do not have the lips needed to suck the teats. Also they could not breathe under water if they were able to suck. To solve these problems, the mother squirts milk into her offspring's mouth by contracting muscles. The young dolphin then goes up to the surface to breathe and then comes down for more. Dolphin milk has 6 times more protein and is much more fattening than human milk. It allows the baby dolphin to increase its weight 2 to 3 times faster than a human baby does during the first six months. Suckling goes on for about a year and a half. After six months, the baby occasionally takes solid food.

Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Protecting: Female); post-independence association with parents; extended period of juvenile learning

Reproductive parameters vary significantly among different populations. Gestation lasts 10-11 months. Lactation lasts up to 19 months, though in at least some areas young may be weaned in 6 months or less. Sexually mature in 5-7 years or more (but apparently 2-4 years in Black Sea). Calving interval averages probably somewhat over 2 years.

Common dolphins face many obstacles at the hands of human beings. They face exploitation by man, entanglements in fishing nets, hunting, as well as other human disturbances. These, however, can be avoided if the dolphin is lucky. Unfortunately, common dolphins, as well as other aquatic life, cannot avoid the pollution that is overtaking their habitats. Many laws have been enacted to protect the dolphins and other marine life.

(Alpers, 1961;   http://whales.ot.com/).

IUCN Red List of Threatened Species: endangered

Accidental.

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: NNA - Not Applicable

Rounded Global Status Rank: G5 - Secure

Reasons: Abundant and widespread, with limited threats.

Listed on Annex IV of the EC Habitats Directive; North and Baltic Sea, western Mediterranean, Black Sea and eastern tropical Pacific populations are listed under Appendix II of the Bonn Convention, and Appendix II of the Bern Convention (7). All cetaceans (whales and dolphins) are listed on Annex A of EU Council Regulation 338/97; they are therefore treated by the EU as if they are included in CITES Appendix I, so that commercial trade is prohibited. In the UK all cetaceans are fully protected under the Wildlife and Countryside Act, 1981 and the Wildlife (Northern Ireland) Order, 1985 (2).

Global Short Term Trend: Relatively stable (=10% change)

Comments: See GABUNDCOM.

Comments: Relatively heavily exploited in the yellowfin tuna industry of the eastern tropical Pacific (1987 kill was estimated at about 20,000; not subject to any particular threat in waters off North America (Gaskin 1992). Some are killed incidental to various fisheries in other parts of the world.

Known threats include entanglement in fishing nets, human disturbance, noise and chemical pollution, lack of food and hunting (3).

A UK Biodiversity Action Plan priority species, the common dolphin is protected in UK waters by the Wildlife and Countryside Act 1981 and the Wildlife (Northern Ireland) Orders, 1985; it is illegal to intentionally kill, injure, or harass any cetacean (whale or dolphin) species in UK waters (2). The Agreement on the Conservation of Small Cetaceans in the Baltic and North Seas (ASCOBANS) has been signed by 7 European Countries, this includes the UK. Provision is made under this agreement to set up protected areas, promote research and monitoring, pollution control and increase public awareness (2).

Common dolphins feed on fish. This can be a problem for those trying to catch the fish on which these dolphins are preying. In fact, the United Nations reported that dolphins along the California coast eat an average of 300,000 tons of anchovies each year, whereas commercial fisherman take in only 110,000 tons. Because of this, many angry fisherman who catch these enemies in their nets often kill them.

(Allen, 1979;   http://whales.ot.com/).

Common dolphins are a very helpful and friendly species. They have been known to rescue humans. They also provide entertainment for sailors as they play along the sides of their ships. Furthermore, fisherman use common dolphins in trying to locate fish. In some cultures, such as on the Polynesian Gilbert Islands, dolphins are also eaten as food.

(Alpers, 1961).

Comments: Small numbers are taken directly, mainly for human consumption or animal feed, in many parts of the range (IUCN 1991).

subpopulation Mediterranean common dolphin : Endangered (EN)

Least Concern (LC)