Spinner Dolphins belong to the Delphinidae family and are distinguished by their elongated snouts. They have been named due to their incredible tendency to spin in the air while leaping out of the water.
Table of Contents
Scientific Classification
Animalia
Chordata
Mammalia
Cetacea
Delphinidae
Stenella
Stenella longirostris
Table Of Content
Table of Contents
Scientific Classification
Animalia
Chordata
Mammalia
Cetacea
Delphinidae
Stenella
Stenella longirostris
Table of Contents
They are small sized dolphins that live in tropical and subtropical waters all over the world.
Description
Size
The adults vary between 4 to 7 feet in length, approximately.
Weight
It may range between 25 and 79 kg.
Shape
It has a slender body, in which the rostrum is elongated and black in color.
They have three shades of grey on the body. The sides of its body are not as dark as the dorsal region which is dark grey, and the belly area it is usually white or light grey.
A deep bar exist from the flipper to the eye of the animal.
Subspecies
There are four subspecies of this dolphin, namely:
Eastern Spinner Dolphin
Central American or Costa Rican Spinner Dolphin
Dwarf Spinner Dolphin
Gray’s or Hawaiian Spinner Dolphin
Distribution
Hawaiian islands, Caribbean, Gulf of Mexico including mid-Atlantic up to the northwestern African coast. In the tropical Indian Ocean, they are highly prevalent in the oceans and close to the islands of Maldives and Sri Lanka.
There is no data of a Spinner Dolphin population present near Australia.
Range
Spinner Dolphins are distributed over a large range all over the world around central and eastern Pacific, Indian Ocean and tropical Atlantic Ocean. Sub-species have been known to exist in the gulf of Thailand as well. Both subtropical and tropical waters are frequented by them in both hemispheres.
Spinner Dolphin Picture
Habitat
Spinner Dolphins are comfortable in inshore waters and banks in tropical waters. They require shallow bays for resting in Hawaii but otherwise also flock on high seas away from shores in the eastern Pacific.
It has been noted that they travel offshore after spending the day time in the bay region. The intensity of the lagoon current often determines its presence in the area.
Diet
Spinner Dolphins generally eat small fishes, sergestid shrimps, and squids. These carnivores take feeding expeditions during the night. They are however not fussy and can change their food pattern according to the availability of prey.
Sounds
Spinner dolphins use whistles to communicate with each other. They have ‘signature whistles’ that are emitted from their blowholes (producing visible bubbles).
Behavior
Some of the spinner dolphin’s behavioral characteristics:
They perform amazing acrobatics above water, by leaping high and spinning rapidly about seven times, followed with a dive back into the water.
Spinner Dolphins can be found resting in shallow bays in some regions like northern parts of Brazil and Hawaii during the day.
After spending the day in resting mode, they embark on their foraging trips in the evening.
A tendency of returning back to the same site after every foraging spree has been noted in Hawaii.
Though they form families, they also associate with individuals outside their families or groups.
These dolphins are not loyal to a single partner but mate with different partners during the mating season.
Dolphins that share special bond can be seen swimming together, twisting and turning with apparent glee.
They only allow a part of their brain to sleep at a time, in order to keep breathing in the water while they are asleep.
Spinner Dolphin Jumping
Individuals sometimes indulge a series of somersaults in the air, known as head-over-tail leaps.
When changing traveling direction, tail slaps are observed which acts an acoustic signal to the other individuals in the pod.
Pacific Spinner Dolphins make close associations with yellow-fin tuna and pantropical spotted dolphins.
They can dive almost 300 meters to feed.
Mating Season
Spinner dolphins do not have a distinct mating season.
Breeding
Female spinner dolphins reach sexual maturity between the age of 4 and 7, after which they are capable of reproducing. For the males to mate, they have to wait longer, as they attain sexual maturity between 7 and 10 years of age.
They reproduce every 2 or 3 years and gestation time is 10 months, after which a single calf is born. The calves derive nourishment from their mother’s milk till they are 2 years of age.
Adaptation
To breathe without coming to the surface of the ocean, they blow bubbles through which they breathe.
An organ located in its head emits the sounds which enable their echolocation.
It has pointed teeth in the snout which intertwine to grasp the prey, which it gulps down without chewing.
Its tail has flukes which are moved up and down by the muscles in the back while swimming.
Life Span
They can live as long as 20 years.
Life Cycle
The calves are born with wrinkles that are folds from the womb itself. They have limp dorsal fins and folds on the sides. It slowly gains rigidity in the dorsal fins as they mature.
Spinner Dolphin Image
Why do Spinner Dolphins spin?
There might be different reasons for their spinning. It might be done to get parasites off their body, or as a ritual of courtship. Another cause cited is that by spinning it emits water from respiratory tract.
Predators
These marine mammals are at risks from sharks, killer whales, short finned pilot whales, pygmy killer whales and false killer whales.
Parasite attacks are also common which include both internal and external parasites.
Conservation Status
IUCN Redlist classifies them in the “Data Deficient” category.
The Convention on the Conservation of Migratory Species of Wild Animals or CMS has listed the populations of the eastern Pacific and that of Southeast Asia as the ones requiring protection.
They are not listed as ‘Endangered’ species anywhere but are listed in CITES’ Appendix II.
Interesting Facts
Their scientific name is Stenella longirostris. ‘Longirostris’ is a term which means ‘long-beaked’ in Latin.
They only require less than 1 second to drain their lungs of air and refill them, when they breathe.
During breathing, the air from the blowhole is ejected at a speed which exceeds 100 miles per hour.
Sense of taste or smell doesn’t seem to be prevalent in them.
To satisfy their energy requirements, adults must consume more than one prey per minute.
