Short-Beaked Common Dolphin, Delphinus delphis
The short-beaked common dolphin (Delphinus delphis) is a species that can be found in warm temperate and tropical waters. Its range is larger than that of the long-beaked common dolphin and includes the Mediterranean and Caribbean Seas, but it is not thought to occur in the Indian Ocean. This species is classified within the Delphinus genus along with the long-beaked common dolphin. Both of these species were classified under one species, named D. delphis, until it was found that both were distinct enough to deserve their own species classifications.
The short-beaked common dolphin is moderately sized, reaching an average body length between 5.2 and 6.6 feet with a weight between 150 and 520 pounds, although weights between 150 and 240 pounds are more common. Males typically grow larger than females, displaying a sexual dimorphism. It is very similar in appearance to the long-beaked common dolphin, with darker coloring appearing on the back and lighter coloring appearing on the underbelly. There is an hourglass shaped marking on each side, which can vary between light grey, yellow, or white in the front and darker grey or black in the back.
As is typical to dolphin species, the short-beaked common dolphin is highly sociable and will gather in groups of up to thousands of individuals, although groups containing hundreds are more common. Like its relative the long-beaked common dolphin, it swims alongside pilot whales and baleen whales, and can be seen at the bows of ships. It consumes many types of squid and fish that can be found at depths of up to 660 feet.
The short-beaked common dolphin has a pregnancy period that lasts between ten and eleven months, resulting in the birth of one calf. The calf weighs around 22 pounds at birth and can have an average body length between 2.3 and 3.3 feet. Weaning occurs at different points for calves of this species, depending upon their location. Calves in the Black Sea population are weaned at around five to six months of age, but weaning can occur at up to eighteen months of age in other areas. The period between pregnancies can also vary between one and three years depending upon the population. Sexual maturity varies depending upon location and occurs between two and seven years of age for females and three to twelve years for males. The Black Sea population of short-beaked common dolphins will typically live for 22 years, while other populations can live to be 35 years old.
The short-beaked common dolphin appears on the Convention on the Conservation of Migratory Species of Wild Animals (CMS) in different areas depending upon the location. The Mediterranean population is listed on Appendix I, while the Baltic Sea, North Sea, Black Sea, and eastern tropical Pacific populations appear on Appendix II. Its Appendix I listing gives it a nearly extinct status, and experts work closely to save the populations found on it. The Appendix II listing means that this species has been found to have an unfavorable status, so research and conservation efforts should be conducted in order to sustain the species’ population numbers.
The short-beaked common dolphin is also protected by the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area or ACCOBAMS and by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas or ASCOBANS. It is also found in the Pacific Cetaceans MoU and the Western African Aquatic Mammals MoU. The short-beaked common dolphin appears on the IUCN Red List with a conservation status of “Least Concern.”
Image Caption: Common dolphin. Credit: NOAA, Scott Hill/Wikipedia