Delphinus delphis are very closely related to D. capensis Gray (Long beaked common dolphin). Short-beaked common dolphins are small dolphins measuring between 1.7 and 2.5 m long, weighing up to 200 kg, and reaching ages above 30 years. As adults, the males are slightly larger than the females. They have a rounded melon, moderately long beak (rostrum), and a tall pointed dorsal fin. This species can be identified by its distinct bright coloration and patterns (1). They are black to dark grey dorsally, white ventrally, with a characteristic ‘hourglass’ shape on flanks, half yellow at the head, half light grey towards the fluke. A black stripe runs from the pectoral fin to lower jaw and from eye to eye across the base of the melon.
Common dolphins inhabit pelagic and offshore environments, rarely coming shallower than 180m (2), but stick mostly along the continental slope in waters 200-2,000 m deep (1). They occur in all tropical, subtropical and warm temperate seas, with a wide distribution in the eastern North Atlantic Ocean, but prefer waters that have a surface temperature higher than 10°C (2). In the western North Atlantic, they are often associated with the Gulf Stream Current. Short-beaked common dolphins also prefer waters altered by underwater geologic features where upwelling occurs (1).
Males become sexually mature between 3 to 12 years and females between 2 to 7 years. Breeding usually takes place between the months of June and September, followed by a 10-11 month gestation period. Females give birth to a single calf every 1-3 years, and lactation lasts approximately 4 months (1).
The abundance and distribution of short-beaked common dolphins will vary based on inter-annual changes, oceanographic conditions and seasons. They can occur on the continental shelf or farther offshore throughout the Atlantic and Pacific Oceans. Other distinct populations can be found off of northern Europe, the Black Sea, Newfoundland, the Mediterranean Sea, Africa, the south western Pacific, southern Australia, and New Zealand (1). In addition, scattered populations have been found in the Indian Ocean and waters near Japan. They seldom venture into the Arctic (4). Once, one of the commonest species in the Mediterranean Sea, the Common Dolphin has experienced a generalized and major decrease in this region during the last 30–40 years (3).
Common dolphins travel in large ‘pods’, often containing 50-70 individuals, although sometimes more (4). Migration routes are not well known and common dolphins are present year round in some parts of their range. Seasonality in prey availability may explain their migrations. Sightings in the western Mediterranean also indicate seasonal patterns in distribution. Common dolphins are more frequently observed in the southern part of the Mediterranean during the first half of the year. In the northern part of the Sea, sightings increase during the second half of the year (4).
These fast-swimming dolphins are highly active, often leaping clear of the water (breaching), and slapping their flippers on the water surface (lobtailing) (2), porpoising, somersaulting, and other frequent surface active behaviours. They will often approach ships and even large whales to bowride for long periods of time (1).
They occur in large groups of several hundred individuals (1), the size of group depends on both the time of day and year. Mediterranean Common Dolphins are typically found in groups of 50–70 individuals, with larger aggregations occasionally recorded. In the eastern Ionian Sea coastal waters, however, groups rarely include more than 15 individuals, and groups greater than 40 have not been observed.
Mixed-species groups of Common, Striped (Stenella coeruleoalba Meyen) and Risso’s Dolphins (Grampus griseus Cuvier) have been consistently observed in the pelagic waters off Greece (3). The approach of these groups can be detected from miles away, and some noises made by this species can be heard from above the surface of the water, and are used in co-operative methods of hunting (2). Short-beaked common dolphins are capable of diving to at least 650 ft (200 m) to feed on fish from the deep scattering layer at night, and usually rest during the day (1). They make short dives typically of between 10 seconds and 2 minutes, but dives lasting for as long as 8 minutes have been recorded (2).
The common dolphin will feed on fish, including herring, sardines and pilchard, and also feed sometimes on squid.
IUCN Red List = Endangered (3)
National Endangered Species Act lists them as vulnerable
The Barcelona Convention
The Bonn Convention Appendix II (5)
Natura 2000 network under the 9243 EEC “Habitats” Directive
The Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS 2002) considers the Mediterranean Common Dolphin as an endangered population
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 Bern Convention
Annex A of EU Council Regulation 338/97
CITES Appendix I
Description written by Jo Pollett (2009)
(1) NOAA Fisheries (2009) Common Dolphin (Delphinus delphis – Office of Protected resources [online] Available:
http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/commondolphin_shortbeaked.htm [date accessed: 02/06/2009]
(2) ARKive (2009) Short-beaked Common Dolphin- Delphinus delphis [online] Available:
http://www.arkive.org/short-beaked-common-dolphin/delphinus-delphis/facts-and-status.html [date accessed: 02/06/2009]
(3) IUCN (2009) IUCN Red List of Threatened Species [online] Available:
http://www.iucnredlist.org [date accessed: 26/05/2009]
(4) Encylopedia of Life (2006) Delphinus delphis, Linnaeus 1758 [online] Available:
http://www.eol.org/pages/314276?category_id=70 [date accessed: 02/06/2009]
(5) Convention on Migratory Species (2004) Delphinus delphis, Common dolphin [online] Available:
www.cms.int/reports/small_cetaceans/data/d_delphis/d_delphis.htm [date accessed: 02/06/2009]