Striped dolphin
Striped dolphins (Stenella coeruleoalba) in the eastern tropical Pacific Source: NOAA National Marine Fisheries Service
The Striped dolphin is a marine mammal within the family of oceanic dolphins, part of the order of Cetaceans, that is found in warm-temperate and tropical waters of all of the world's oceans between 50°N and 40°S .
 Striped dolphin (Stenella coeruleoalba) in the eastern tropical Pacific . Source: NOAA National Marine Fisheries Service
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 Size comparison of an average human and a striped dolphin (Stenella coeruleoalba). Source: Chris Huh
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| Conservation Status Data Deficient |
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Scientific Classification Kingdom: Animalia (Animals) |
| Common Names: Blue dolphin Blue-white dolphin Euphrosyne dolphin Gray's dolphin Streaker Streaker porpoise Striped dolphin |
Contents
Physical description
With the classic dolphin shape, the striped dolphin's most remarkable feature is the distinctive pattern of blue and white stripes running across the entire length of the body, from the eye to the anus, and because they possess black flipper stripes. It is mainly blue with a white to light grey stripe following the spine. The sides are darker than the belly.
Stenella coeruleoalba ranges in body length from 220 to 236 cm. Like many other delphinids, striped dolphins have a fusiform body, tall dorsal fins, long, narrow flippers, and a prominent beak (Archer and Perrin, 1999). Stenella coeruleoalba can be distinguished from other delphinids by their distinctive color and stripe patterns.
Reproduction
The age of sexual maturity is quite variable within sexes. Males reach sexual maturity between the ages of seven and fifteen, and females become sexually mature between five and 13 years of age. The mating season of the striped dolphin is in the winter and early summer in the western north Pacific, while it occurs in the fall in the Mediterranean (Archer and Perrin, 1999). The gestation period of striped dolphins lasts 12-13 months. Females typically have a four year calving interval, having a resting period of approximately two to six months between lactation and the next mating (Calzada et al., 1996).
Fetuses grow at an approximate rate of 0.29 cm/day. At birth, striped dolphins are 90-100 cm long (differing slightly between ranges) and have body mass approximately 11.3 kg (Calzada, Aguilar, Sorensen, and Lockyer, 1996). Young calves then nurse for almost 16 months. (Archer and Perrin, 1999; Calzada et. al., 1996).
Behavior
Group size in Stenella coeruleoalba ranges from a few individuals to over one-thousand individuals, but most schools consist of 100-500 dolphins. Three different kinds of schools often occur: juvenile, breeding adults, and non-breeding adults. Calves do not usually join the juvenile school until one or two years after weaning (Archer and Perrin, 1999). As females reach the transition stage between juvenile and adult, they usually join the non-breeding adults, only a small number go straight to the breeding school. However, as males join an adult group, equal numbers tend to join the breeding and non-breeding schools (Archer and Perrin, 1999).
Striped dolphins are very active, performing aerial maneuvers such as breaching (jumping out of the water), chin slaps, bow-riding (swimming along the wave created by a boat or ship, while often twisting and jumping) and a unique behavior called "roto-tailing," in which "they make high arcing jumps while violently and rapidly performing several rotations with the tail before reentering the water" (Archer and Perrin, 1999).
A highly gregarious animal, the striped dolphin may associate in schools of over 1000, but is more usually seen in same-age groups of 100 to 500 individuals. It is a very active swimmer, performing leaps and breaching frequently. Communication between striped dolphins is by clicks and whistles.
Striped dolphins provide much entertainment to sailors and travelers, as they flip, twist, and breach alongside the waves created by ships and boats. In addition, they are sometimes hunted for meat.
Distribution
Stenella coeruleoalba is found in warm-temperate and tropical seas throughout the world between 50°N and 40°S. Stenella coeruleoalba has been observed in the Mediterranean Sea, eastern and western Pacific Ocean, Atlantic Ocean, Indian Ocean, Caribbean Sea, and in the northern Gulf of Mexico (Baird et. al., 1993; Archer and Perrin, 1999).
Habitat
Striped dolphins occupy both offshore and inshore warm-temperate and tropical waters. Stenella coeruleoalba appears to avoid sea surface temperatures of less than 20 degrees Celsius. (Van Waerebeek et. al., 1998) This cetacean Inhabits both temperate and tropical pelagic waters
Feeding habits
Stenella coeruleoalba seems to have an opportunistic feeding habit. Examining the stomach contents of many striped dolphins, researchers have found Stenella coeruleoalba to mainly feed on cephalopods, crustaceans, and bony fishes (Wuertz and Marrale, 1993). There is some variation in diet between ranges of Stenella coeruleoalba. Mediterranean (Mediterranean Sea) striped dolphins seem to prey primarily on cephalopods (50 to100% of stomach contents), while northeastern Atlantic striped dolphins most often prey on fish, frequently cod (Archer and Perrin, 1999). The ranges of observed prey indicate that striped dolphins primarily feed in pelagic or benthopelagic zones of the ocean, often along the continental slope (at the edge of the continental shelf where the ocean floor plunges steeply four to five kilometers) (Archer and Perrin, 1999).
Conservation status
IUCN Red list classifies the Striped dolphin as. Low risk
Threats
Once a substantial threat, bycatch has been reduced from 14,000 striped dolphins a year between 1950 and 1969 in the western Pacific, to a current incidental catch of 2000 to 4000 individuals. Fishermen kill dolphins caught in their nets as they present competition for fish. Hunting has also been known to take place, particularly in Japan, but is not considered a major threat, and Japan has voluntarily reduced its catch. Water pollution as a result of the release of heavy metals causes lung disease, and the over-fishing of anchovies has harmed populations in some areas. In the [[Mediterranean (Mediterranean Sea)] Sea], a morbillivirus caused the death of more than 1000 animals between 1990 and 1992. The epidemic was possibly caused by poor environmental conditions.
Other threats include habitat degradation, taking by commercial fisheries, and killing dolphins for their meat, all of which activities contribute to Striped dolphin population declines.
References
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