Striped Dolphin

Classification

Class: Mammalia
Order: Cetacea
Suborder: Odontoceti
Family: Delphinidae
Genus: Stenella
Species: coeruleoalba
Common Names: Striped dolphin; Euphrosyne dolphin; Blue white dolphin
Irish Name: An deilf stríocach
 

Key Identification Features

Maximum body length: 2.6m (8.5ft)
Average body length:2m (6.5ft)
Head Shape: Rounded head which tapers
Beak: Prominent long slender beak.
Dorsel fin: Tall and curved.
Coloration: Dark blue grey cape, the flanks are a lighter grey, leading to pink-white undersides and black pectoral fin.
Markings: There are a number of dark stripes, one running from the eye to the anus (between the grey and white areas), and others running from the eye backwards on the white ventral surface, often linking with the pectoral fin.
 

Field Identification

The striped dolphin has a streamlined body, with a long slender beak and a black stripe from the eye to the flipper. They have dark flippers, tail and fin. The striped dolphin is a fast active swimmer who often bow-rides. In poor light they will resemble the common dolphin.
 

Species Similar in Appearance

Most easily confused with its closest relative the common dolphin. They are similar in every respect (shape, size and behaviour) but have very different colouration/markings
 

Behaviour

Striped dolphins are very agile and highly active animals, which can be observed exhibiting the following behaviour.

  • Tail spinning: Spinning on it's tail at the surface of the water
  • Somersaulting: Leaping and spinning at heights out of the water
  • Breaching: Jumping completely out of the water
  • Bow riding: Swimming alongside fast moving boats.

 

Status and Distribution

Striped dolphins are considered common and are found in most warm or temperate waters. Large concentrations are found in the Mediterranean and Bay of Biscay
 

Where and When Best Seen in Ireland

Confirmed sightings of this warm water, pelagic species are not common in Irish waters, although a number of sightings occur each year, most notably in offshore waters off the southwest coast.
 

Food and Feeding

Their diet consists of fish, squid or octopus and shrimps, as well as krill and other crustaceans.
 

Social Structure

Striped dolphin groups range from a few animals to a few thousand, but most often their groups range from between 100-500 individuals. Within these groups there are a number of segregations, which make up smaller groups depending on age, sex and status. These are adult breeding, adult non-breeding, mixed breeding, mixed non-breeding and juvenile. These schools are constantly changing. In the adult breeding schools it is not uncommon for the males to leave after mating. It then becomes an adult non-breeding group. When the calves are born, it turns in to a mixed non-breeding group and then a couple of years after weaning the calves will form juvenile schools. As the juveniles reach sexual maturity they are accepted into adult breeding or non-breeding groups. The females are accepted first, followed soon after by the males.
 

Conservation Issues

Like many other cetaceans, entanglement in fishing nets is the main threat to the striped dolphin.

Although the striped dolphin is considered common, drive fishing, such as those in Japan, where entire schools are driven ashore and killed for their meat is a problem. Thousands of striped dolphins are killed every year in this way.
 

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