Common Dolphin

Common Dolphin

Tim Hauf, timhaufphotography.com

Scientific Name
Delphinus Capensis

Introduction
Common dolphins can be split into two groups long and short beaked. Both groups are found throughout the world’s oceans and share similar behavioral characteristics such as jumping and surfing the bow waves of vessels. However, the long beaked dolphins, delphinus capensis, are more commonly seen near coastal areas.. Both forms have a dark gray dorsal surface with a lighter hourglass pattern on their sides, and white undersides.

Quick and Cool Facts

• Common dolphins are one of the most numerous cetaceans in the world, with a population that is estimated to be over one million. ²
• Until recently, the long-beaked common dolphin was not considered a valid species, (and was grouped with the short-beaked dolphin) however, in 1994, it was demonstrated that it is indeed a valid species. ³
• These dolphins have an estimated lifespan of approximately 40 years. ¹
• Long-beaked common dolphins are gregarious. Schools range from less than ten to several thousand. ³
• Hybrids between this species and common bottlenose dolphins have been born in captivity.3
• Long-beaked common dolphins have more teeth than any other species of dolphin ⁵
• The species name capensis refers to the Cape of Good Hope. ⁵
• Long-beaked common dolphins are capable of diving to at least 900 feet and holding their breath for up to 8 minutes to feed on prey. ⁵

Appearance
As described by the FAO Species Identification Guide: Marine Mammals of the World, “The common dolphin is a moderately slender animal (although some offshore animals are rather stocky) with a medium to long beak and a tall, slightly falcate dorsal fin. Common dolphins are strikingly marked, with a dark brownish grey back, white belly, and tan to ochre anterior flank patch. This flank patch dips below the dorsal fin and combines with streaks of light grey on the tail stock to produce the species’ most characteristic feature, an hourglass pattern on the side. The lips are dark, and there is a stripe running from the apex of the melon to encircle the eye. There is also a black to dark grey chin-to flipper stripe, and sometimes a thinner stripe running towards the area of the anus. There are 40 to 61 small pointed teeth per row. ¹

Common dolphins are highly geographically variable and many regional forms have been described. In several parts of the world, two types of common dolphins appear to exist: a long-beaked coastal type (generally with a muted color pattern), and an offshore type with a shorter beak (the latter comprises several stocks in the eastern tropical Pacific). Recent research indicates that these two types represent separate species. ^1,3

Range
According to NOAA’s Office of Protected Resources, The long-beaked common dolphin has a restricted distribution in the Atlantic, Indian and Pacific Oceans. Long-beaked common dolphins are commonly found along the U.S. west coast, from Baja California (including the Gulf of California) northward to about central California. Distinct populations can be found off the coasts of California and Mexico, South America (Peru, Chile, Venezuela, Brazil, and Argentina) -- The abundance and distribution of this species may change with varying oceanographic conditions. ⁵

Habitat
Long-beaked common dolphins generally prefer shallow, tropical, subtropical and warmer temperate waters closer to the coast, usually within 50-100 nautical miles and on the continental shelf. ⁵ These parameters of adaptation for this species make the Southern California Bight and ideal fit.

Feeding
Long-beaked common dolphins are capable of diving to at least 900 feet and holding their breath for up to 8 minutes to feed on prey. The NOAA Fisheries Office of Protected Resources states that the majority of their diet consists of small schooling fish such as anchovies and sardines. Krill and cephalopods (e.g., squid) also comprise and important part of their diet. Dolphin groups may work together to herd schools of prey. This species has 47-67 pairs of small sharp conical teeth in each jaw used for grasping prey. ⁵

Reproduction
As stated in Marine Mammals of the World, in a 2008 publication by Jefferson, T. A, M. A. Webber, and R. L. Pitman, Long-beaked common dolphins become sexually mature at around 6.5 feet in length. Breeding usually takes place between the spring and autumn, followed by a 10-11 month. gestation period. Females give birth to a single calf that is about 2.5-3 feet long and weighs about 20 lbs, and have an estimated calving interval of 1-3 years. ^{1, 5}

Conservation Status
The long-beaked common dolphin is covered by the Marine Mammal Protection Act. The International Union for Conservation of Nature and Natural Resources, (IUCN), states that although the species is widespread and its aggregate abundance probably numbers in the high tens or low hundreds of thousands, in several areas (most notably West Africa, the east and west coasts of South America and East Asia) there are known incidental and directed takes of unknown, but possibly large, magnitude, making it difficult to make a reliable assessment of the impact on the species. Therefore, the Long-beaked Common Dolphin is listed as Data Deficient. ⁶

References and Additional Information

1. FAO Species Identification Guides: Marine Mammals of the World
2. Channel Islands National Marine Sanctuary
3. The Society for Marine Mammalogy
4. Wildscreen Arkive
5. NOAA Fisheries Office of Protected Resources
6. International Union for Conservation of Nature and Natural Resources, (IUCN),