Striped Dolphin - Stenella coeruleoalba

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Striped Dolphin - Stenella coeruleoalba.



Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Eutheria
Order: Cetacea
Suborder: Odontoceti
Family: Delphinidae
Genus: Stenella
Species: Stenella coeruleoalba


Key Facts
Size: Up to 2.5 metres, female larger
Range: Throughout all the tropical and warm temperate oceanic zones
Threats: Caught in fishing nets
Diet: a variety of small, deep water shoaling fish and squid

Physical description
The striped dolphin is slender and streamlined with a well-defined beak. The beak is long and thin and there are about 50 cone shaped teeth on both jaws. The dorsal fin is placed mid-way down the body and is falcate. The pectoral fins are short and the tail fluke has a pronounced notch. Most noticeable are the two very well defined black or blue/black stripes, the first running form the corner of the eyes down to the anal region and the second from the eye to the pectorals. Sometimes these lines are double and there is usually a falcate area under the dorsal fin which also points to the eye. The fins, flukes, beak and jaws are all dark whereas the belly is pale.

Distribution
The striped dolphin is found in tropical and temperate waters of all oceans. In the Atlantic its northern limits are Newfoundland and Greenland. In the Pacific it is found as far North as Hokkaido or Washington. Southwards it is found all around Australia and New Zealand and South Africa as well as off the east coast of South America to the same latitudes. However on the west coast of South America it has not been found so far south. The striped dolphin prefers deep water and is rarely found in coastal areas. It carries out a local migration around the equator in the autumn, travelling towards the cooler latitudes in the spring.

Behaviour
Striped dolphins are very acrobatic, leaping up to 7 metres out of the water. They travel in very large groups of up to 100 individuals and are attracted by ships. Like many dolphins they enjoy bow riding but have a habit of suddenly “streaking” away from the ships. They can attain speeds of up to 37 km/hr, surfacing every five seconds. When travelling more slowly they surface roughly about every 10 to 20 seconds. There is no data at present about their use of sound.

Breeding
The large mixed schools of striped dolphins appear to be sub-divided into smaller breeding or non-breeding schools and mating is seasonal. The calving interval is thought to be about four years. Gestation lasts about 12 months and the young are between 93 and 100cm at birth. Females become sexually mature earliest, between 5 and 13 years, and the males between 7 and 15 years. Their maximum estimated age is 58 years.



Feeding
As one would expect from a species which has such a large range, the striped dolphin eats a large variety of foods. It seems to prefer feeding on shoals of small, deep sea fish, as well as squid and octopus. They can dive to depths of 200 to 700 metres but in the Atlantic their main prey seems to be cod.

Current situation
On a global scale the striped dolphin remains abundant. However, in some regions there is concern due to large numbers being killed in drift-netting for tuna and swordfish. Over fishing of their prey such as squid and cod seems to have led to striped dolphins being poorly nourished and therefore being more susceptible to disease. Around Japan the striped dolphin has been subjected to very intensive hunting in the past and they are seldom found in those waters now.

From Carnivora.

carnivora.net/striped-dolphin-stenella-coeruleoalba-t2770.html

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Striped Dolphins

The Striped Dolphin (Stenella coeruleoalba) is an extensively studied dolphin that is found in temperate and tropical waters of all the worlds oceans. Striped Dolphins can be found in both the Atlantic and Pacific oceans, usually offshore, though sometimes in deeper waters closer to shore.
The ancient Greeks even observed these dolphins in the Mediterraean, and often painted pictures of them.

STRIPED DOLPHIN CHARACTERISTICS
The Striped Dolphin is easily recognized by the dark blue stripe that runs from their dark coloured rostrum, around their eye, and down along their side to their rear flank. Another darker patch runs from their melon along their back to their dorsal, ending just behind their dorsal fin, with one portion sweeping forward on the body.
The underside is usually considerably lighter in colour – either white or pinkish. Colouration between individuals can vary greatly, with some looking grey in tone while others are more brown. Even within these two colours the tone of the colour varies, with some being lighter or darker than others. There is also a dark blue patch around the eyes. The lips are white. The tail stock is the same mid-blue colour as the middle stripe of the flank.
By adulthood Striped Dolphins have grown to 2.4 metres (females) or 2.6 metres (males) and weigh 150 kilograms (female) or 160 kilograms (male). Research suggest that sexual maturity is reached at 12 years in Meditterranean females and in the Pacific at between 7 and 9 years.

STRIPED DOLPHIN BEHAVIOUR
In common with other dolphins in its genus, the Striped Dolphin moves in large groups – usually in excess of 100 individuals in size. Groups may be smaller in the Meditterranean and Atlantic. Striped Dolphins may also mix with Common Dolphins and might even be confused as a common dolphin from a distance, but they lack the distinctive yellow hourglass shape on the side. Striped dolphins are also generally darker than a Common dolphin.
The Striped Dolphin is as capable as any dolphin at performing acrobatics – frequently breaching and jumping far above the surface of the water as high as 23 feet.

Striped Dolphins sometimes approach boats in the Atlantic and Meditterranean but this is dramatically less common in other areas, particularly in the Pacific where it has been heavily exploited in the past.

STRIPED DOLPHIN DIET
A widely distributed species such as the Striped Dophin tends to include a high diversity of organisms in its diet. These include a variety of shoaling fish and cephalopods (squid and octopus) concentrating on those species occurring in large dense schools.

STRIPED DOLPHIN COMMUNICATION
Like other dolphins, Striped Dolphins use echolocation, a way of sensing in which they emit high-pitched clicks and sense them as they bounce back off objects (like prey).

STRIPED DOLPHIN REPRODUCTION
Gestation lasts approximately 12 months for the female Striped Dolphin and there is a 3 or 4 year gap between calving. Life span of the Striped Dolphin is about 55 – 60 years.

STRIPED DOLPHIN PREDATORS
Some sharks (including tiger sharks, dusky sharks and bull sharks) and orcas will prey upon dolphins. Dolphins are also often trapped in fishing nets.

STRIPED DOLPHIN CONSERVATION
The Striped Dolphin is an abundant species. It has had some of regional population loses such as the drive fisheries practiced in Japan and the mysterious die off of more than 1000 individuals in the Mediterranean. Fishing industry practices still cause some deaths through entanglement and indirectly impact on some populations by depletion of their food resource.

STRIPED DOLPHIN AND HUMANS
Japan has hunted Striped Dolphin in the western Pacific since at least the 1940s. During the ‘Striped Dolphin drive’ heyday at least 8,000 – 9,000 species were killed each year and in one exceptional year 21,000 individuals were killed.
Since the 1980s, following the introduction of quotas, this number has fallen to around 1,000 kills per year. Conservationists are concerned about the Meditterranean population which is threatened by population, disease, busy shipping lanes and heavy incidental catches in fishing nets.
Attempts have been made to keep the Striped Dolphin in captivity. However these have all failed, with animals dying within 2 weeks due to failure to feed.

animalcorner.co.uk/animals/striped-dolphins/

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Striped dolphin strands alive in Cornwall

January 2008. A male striped dolphin, a relatively uncommon sight in inshore Cornish waters, has stranded alive on the south coast. A member of the public reported the dolphin to British Divers Marine Life Rescue (BDMLR).

Trained volunteers arrived on the scene at Church Cove, Gunwalloe, near Helston, to find the dolphin lying on the beach not far from the surf. It was almost certainly stranded on the outgoing tide. At first sight, it looked relatively unscathed and the volunteers followed their usual procedure of trying to keep the animal as comfortable as possible, covering him with a light sheet and keeping him wet to prevent his skin from drying out in the wind. The dolphin remained calm throughout and the volunteers had hoped that the animal was in good enough condition to be refloated, once a vet had examined it.

Badly Injured
James Barnett, the veterinary coordinator for BDMLR, carefully examined the dolphin and assessed its state of health. ‘Initially, the animal looked in reasonably good condition, although he appeared to be only moderately nourished. He had various abrasions on the edges of his pectoral fins and tail from contact with the rocks, but most of this damage was superficial. However, when I examined his beak, I noticed a large wound on his lower jaw, where a flap of skin and underlying tissue had come away exposing the underlying bone. If this animal had been released back to the sea with this injury, it is highly likely it would have developed osteomyelitis - infection of the bone - and suffered a great deal. So the only option was to put the animal to sleep.’
All those assisting agreed that this was the best course of action to avoid the dolphin from suffering any further. ‘It was a beautiful animal and it's a really difficult decision to make. Naturally we were all sad about it’, said Cheryl Mills, one of BDMLR's volunteers, ‘but the long term welfare of the animal must come first and I'd hate to think that we'd put an unhealthy animal back in the sea to suffer a slow, painful death.’

Marine Strandings Network
Some of the volunteers involved are also members of Cornwall Wildlife Trust's Marine Strandings Network (MSN) and they recorded the animal and took photos of it for the Natural History Museum and Institute of Zoology. Volunteers then transported the dolphin to Truro so that a post-mortem examination could be carried out to try to determine why the animal stranded.

‘We couldn’t see any obvious marks on the dolphin to indicate that it had been caught in fishing gear,’ said Jeff Loveridge of the MSN, ‘and possibly it was diseased. But hopefully the post-mortem will tell us something as we rarely get striped dolphins washing ashore: this is only the 14th striped dolphin we've had in the last five years and it's even rarer for them to strand alive – this is only the second one that we know of in Cornwall.’

‘We're really lucky in Cornwall to have two organisations that work so closely together and share a deep concern for dolphins and seals in the county,’ Jeff continued, ‘and it's amazing how many people will turn out on a week day to do what they can to help or to learn more about these amazing creatures.’


Striped Dolphin Facts
Striped dolphins are very acrobatic, often performing somersaults, tail spins and bow-riding: they have even been known to leap up to 7m out of the water. They are not often seen in coastal waters, preferring deeper, offshore habitat where they feed on pelagic fish, squid and shrimps. They may form very large groups up to 3,000 strong, although 10 - 500 is more normal. These are usually broken up into age groups with mothers and nursing youngsters, immature animals and adults forming separate sections. Groups are seldom seen around Cornwall, however a pod of 40 or more was sighted in June of last year off Lands' End.

www.wildlifeextra.com/striped-dolphin793.html

From Carnivora.

carnivora.net/striped-dolphin-stenella-coeruleoalba-t2770.html