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Common dolphin is the term used for two dolphin species, from the genus Delphinus. According to some sources, there might as well be another third species by the name of Arabian common dolphin, which is debatable. These are medium sized playful dolphins, living in tropical and warm temperate waters.
Common Dolphin is the name of 2 species of dolphins that are scientifically known by the Latin names given below:
- Delphinus delphis (Short-beaked common dolphin).
- Delphinus capensis (Long-beaked common dolphin).
Some studies suggest the existence of a third species known as Delphinus tropicalis but recent studies consider it as a regional variety.
There are stark similarities in the appearance of the 2 species of common dolphins except a few dissimilarities. Take a look at their physical characteristics:
Size : The 2 species of Common Dolphins have a medium size, growing as big as 8.2 ft, with an average of 6 ft approximately. Naturally the only point of differentiation is the size of the beak which is longer in the long-beaked common dolphins.
Weight : Their weight varies between 80 and 150 kg, but it might as well be as heavy as 235 kg. Males are heavier compared to the females. To be precise, Short-beaked ones may weigh around 440 pounds and the long-beaked ones between 170 and 500 pounds approximately.
Color : It is primarily dark on its back and the abdomen is white. On the sides of these common dolphins, there is a pattern in the shape of hourglass composed of yellow and grey at the front and dark grey at the rear.
Rostrums : Their rostrums are thin and elongated with interlocking sharp teeth on every side.
In east Atlantic waters, they inhabit from West Africa to Norway’s southern parts and in West Atlantic, from Florida till Newfoundland. In Pacific, it stretches from Japan till Australia. They are commonly spotted in Australian waters (Tasman Sea and south-east Indian Ocean) barring North Australian regions. They are also seen in Galapagos waters.
Long-beaked ones prefer living in shallow habitats but the short-beaked ones can be found at a depth of around 590 feet as well. Level of shallow water isn’t lesser than 180 m. They can live in cool temperate or tropical offshore waters. They live in open oceans and coastal regions in the Mediterranean. Basically, areas where they can forage on epipelagic fishes are their territories.
Some of their behavioral characteristics are:
- They hunt in schools and generally dives more than 250 meters to bring their prey down.
- They form huge groups known as pods, made of hundreds and thousands of individuals.
- These social creatures indulge in games and activities including bowriding, breaching, pitch poling, porpoising and somersaulting.
- They can swim very fast, often speeding at 65 km per hour maximum and 11 km/hour minimum.
- They can move over escarpments and ridges in the oceans.
- In New Zealand, they have been found to feed along with Bryde’s whales and Australasian gannets apart from which they happen to live with Bottlenose and striped dolphins too.
- They usually eat during the nights, not by chewing them but swallowing them
Common dolphins exchange a range of sounds. They whistle and whine during social interactions which can be specific to a certain pod.
They have a varied diet which chiefly constitutes squids and schools of fishes. Apart from that, they hunt small fishes from the mid water and surface of the ocean. Food behavior is influenced by different locations and seasons. They have been reported to be subsisting on anchovies in the Mediterranean Sea.
They may move around to hunt for food but they are not typically migratory. Beyond Southern California and eastern Pacific, there have been movements based on seasons. Dolphins from north are south bound in Pacific Ocean, as studies have revealed. They have been noted traveling to warmer waters with the change of season. In the months starting from May till October, they have been found visiting oceanic waters off Scotland.
Sharks are the worst enemies of the babies while even as adults they face threats from whales and humans. Their life is at risk from parasites and diseases as well.
These are some of their adaptive features:
- They are endowed with features like well developed throat and larynx to emit calls in high and low pitches helping in eco-location and communication
- They have the ability to arrest breathing for several minutes when they are diving.
- Amazingly, they have adapted the process of blood circulation during diving.
- To breathe in air from the surface, they make use of the blowhole on their head.
- They use their sharp interlocking teeth to catch hold of their prey before devouring it whole by swallowing it.
Season for mating may vary, but usually it happens during spring and fall.
The common dolphins mature at different intervals at different locations. In the Pacific region, the females mature by the age of 7 and males mature between the age of 7 and 12. Mating takes place when become almost 6 ft long. The mother gives birth to her offspring after a gestation period of 11 months. The ones inhabiting the Pacific, takes an interval of 3 years between another birth and those from the Black Sea takes just a year. Both the species have no such marked difference in reproduction pattern.
The calf measures around 3 ft after birth with a weight of 10 kg approximately. Weaning period of the babies also varies largely according to location, from 6 months to 19 months.
It generally lives for 20 years, which may even exceed to 35 years in the oceans.
No sub-species of these dolphins have been reported yet.
They are rarely held in captivity but they are often nursed in zoos only to be later released. Nevertheless, they were exhibited at SeaWorld in San Diego along with Bottlenose dolphins, performing shows like their counterparts.
They have been marked as Least Concern species by IUCN, hence they are not endangered.
Some fun facts for kids are:
- In ancient specimens of art and literary works of Rome and Greece, these dolphins were popularly depicted.
- Maximum time for dives can reach up to 8 minutes but usually it varies from 10 seconds to 2 minutes.
- Among its species, the short-beaked dolphins are more popular globally.
- In the Black Sea they have been called pest due to their massive appetite consuming fish even more than their yearly production.
- Hybrids formed by union of the common dolphins and bottlenose dolphins have also been reported.
- Their feeding behavior might endanger their lives because during their foraging trips they often get captured by fishing gears.
- As per estimates, their population is higher in the eastern Pacific.
- While at sea, they perform different acrobatics by jumping high in the air with their peers.
Take a look at these playful dolphins in these pictures.