Arabian common dolphin
Common dolphins live in both warm-temperate and tropical waters ranging from 40–60°N to 50°S. Long-beaked common dolphins mostly inhabit shallow, warm costal water.
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.
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.
Despite the historic practice of lumping the entire Delphinus genus into a single species, these widely distributed dolphins exhibit a wide variety of sizes, shapes and colors. Indeed, over the past few decades, over 20 distinct species in the genus have been proposed. Scientists in California in the 1960s concluded 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 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. D. tropicalis is a subspecies of D. capensis.
Both common dolphin species are medium-sized; 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 and 518 lb), although the range between 80 and 150 kg (180 and 330 lb) is more common. Males are generally longer and heavier.
Common dolphin have a varied diet consisting of many species of fish and squid. This includes both mesopelagic species and epipelagic schooling species. They have been recorded to make dives up to 200 metres (660 ft) deep.
The short-beaked common dolphin has a gestation period of 10 to 11 months. For the Black Sea population, weaning occurs at between five and six months, but occurs later (up to about 19 months) in other areas. Typical interbirth interval ranges from one year for the Black Sea population to three years for eastern Pacific Ocean populations. Age of sexual maturity also varies by location, but can range between two and seven years for females and three and 12 years for males.
Common dolphins can live in aggregations of hundreds or even thousands of dolphins.They sometimes associate with other dolphin species, such as pilot whales. They have also been observed bow riding on baleen whales, and they also bow ride on boats. They are fast swimmers (up to 60 km/h), and breaching behavior and aerial acrobatics are common with this species. They are also known to display altruistic behaviors to support injured members.