False Bay wildlife - Common dolphins

Common dolphin. 

These intelligent mammals are mystic, marine animals that are playful and lively by nature. Two subspecies of the common dolphin are sighted in the waters of False Bay; the short beaked and long beaked common dolphin with the long beaked the more commonly seen of the two. Dolphins have slender yet firm bodies with a long rostrum (beak) and a blow hole situated on top of their heads to breathe.

Common dolphins are mainly shades of grey and white in colour. The back is grey in colour, stretching from their head to fluke plunging to form a V on each side below the dorsal fin. On either side is an hour glass pattern coloured light grey or yellow in front and dirty grey in back. The dorsal fin is light grey, located near the middle of their back and is triangular, curved shape. The belly is white while their flippers are long, thin and grey in colour.

Habitat

Common dolphins live in salt water around the world, preferring a warmer temperature and so avoid the icy Arctic and Antarctic oceans. The long beaked common dolphin resides in shallow and warm coastal water while the short beaked common dolphin prefers offshore waters, deeper out at sea.

Diet

Common dolphins are active, nocturnal feeders who gather in pods to hunt for squids and small schooling fish such as anchovies, sardines and pilchards.

These dolphins have between 50 to 60 pairs of teeth on both their upper and lower jaw that help to hold their prey. They do not chew their feed, preferring to swallow and so catch prey that is small enough to swallow whole. Common dolphins eat up to about 5% of their body weight on a daily basis.

Behaviour

Pods of dolphins can range in numbers between 100 to 500 and have been seen in the thousands. Dolphins are known to be intelligent and social animals, that thrive on interaction and bonding with one another. They live within a complex hierarchy and tend to create subgroups based on factors such as age and gender.  

Dolphins communicate and hunt using vocalisations and echolocation. Their vocalisation includes making sounds such as whistling, whining and clicking, with languages even differing between pods. Echolocation is a process whereby dolphins send out sounds waves through the water, with the sound hitting an object, bouncing off and echoing back to the dolphin. Dolphins can identify what an object is, such as the shape, size and texture, by the sound of the echo sent back.

Common dolphins are the fastest of all dolphins reaching speeds of up to 40km/h or more. Dolphins are active marine animals; often seen breaching out of the water, somersaulting, bow riding or playing and teasing one another. Bow riding are when dolphins surf in the waves created by boats and ships, with the dolphins propelled forward by the wave.

Dolphin in the womb. 

Reproduction

Female dolphins are called cows and males are called bulls while young dolphins are referred to as calves. Common dolphins become sexually maturity between the ages of 3 to 4 years old or when reaching 1.8 to 2.1 metres in length; whichever comes first. 

Males tend to become aggressive towards other males with regards to potential mating partners, often making sounds to warn each other off and may even collide their bodies against each other. Using their flukes (tails) as a weapon is common to show off their strength. Females choose to mate with the strongest and most dominant of the males. Dolphins, like humans, are known to take part in copulating activities other than for reproduction.

Females give birth to one calf, measuring between 76 to 86 cm, after carrying for 10 to 11 months. The dolphin calf is born tail first instead of head first, and is the only mammal on earth to be born in such a way. During birthing, other dolphins in the pod play a key part, keeping a close circle around the calf and mother for their protection. The dolphins soothe both mother and calf during the birthing process and assist the calf to the surface of the water for its very first breath. Juvenile dolphins stay by the mothers’ side for up to 3 years.

Did you know?

Major threats that common dolphins are faced with include metal and plastic pollutions in oceans and being caught by accident in industrial trawler nets intended to catch fish. 

Common dolphin.