BOTTLENOSE DOLPHIN - Neville Coleman

There are around 14 species of dolphins in the tropical Indo-Pacific area. The common name terms of `dolphin' and `porpoise' have often been confused; the answer is simple.

Porpoises are generally found to the northern hemisphere. The bottlenose dolphin is by far the most well known in the southern hemisphere.

 

Common Name: Bottlenose dolphin
Scientific Name: Tursiops truncatus
Pronunciation: (tur-see-ops) (trun-cate-us)
( photo: Neville Coleman)

The bottlenose dolphin lives in both tropical and temperate oceanic waters and numbers may be seen frequently around continents. It is often seen in bays, harbours and rivers and may exceed 4.5 metres in length. Large schools may contain hundreds but most sightings are of family groups, or pods.

As marine mammals, dolphins must breathe air to stay alive swimming close to the surface to maintain speed and a regular breathing rate. Air is breathed out at the surface and new air taken in before the dolphin dives and in this way it can maintain speeds up to 10 knots over long distances and up to 20 knots for short periods.

Colour alternates between varying shades of grey on the back, grading to white on the belly. The short, stout beak has 23 to 25 pairs of teeth in each jaw and the lower jaw tends to protrude further than the upper. The body is smooth and streamlined, similar in many respects to a fish, but all aquatic mammals are thought to have originated from land dwelling ancestors, hence the tail flukes are in a horizontal position.

Bottlenose dolphin holding its position by 'tail-standing' on a table coral waiting for the school of trevally it has been 'play-hunting' to swim by. As the school passed, the dolphin launched itself into the school scattering fish everywhere. The dolphin made no attempt to catch a fish during this behaviour and as soon as the school closed ranks again, the dolphin would repeat the process all over again.       ( photo: Neville Coleman) 

Bottlenose dolphins feed mainly on schooling fishes which they often herd towards the surface to allow easy feeding. Although their eyesight both in and out of the water is extremely acute they rely mainly on their highly sensitive and accurate echo-locating system to seek out their prey.

It was a magic scene, at no time did the dolphin appear to be at all serious in its 'play-hunt' proceedures. After watching for 10 miutes it became clear to me that the dolphin could catch any trevally it wanted with hardly any effort on its part. The fish had no idea whether the dolphin was just playing , or serious, so they did not seem to regard the dolphin as a threat. Every now and again the dolphin would grab a fish, bite it in half, and only swallow the piece in its jaws. The other half just drifted to the bottom.( photos: Neville Coleman)

Reaching sexual maturity at an early age, bottlenose dolphins are capable of reproduction at 14 months. The sexes are separate and mating is only carried out after a period of courtship. Copulation occurs while swimming with the female usually taking the above position and the male below in an upside down position.

Gestation is usually over a period of nine to 15 months after which time the female gives birth to a single calf. The young is born tail first and is able to swim immediately after birth. Like all mammals, the female bottlenose dolphin suckles its young from a milk gland on the underside in the vicinity of the chest. Young dolphins remain dependent on milk for up to one year after which they are weaned towards a diet of fish.

Newly born, this very young dolphin has darker bands around it.  The mother was teaching it to stay beside her. Here, she actively pushes the young one high above the surface in what appeared to be a reinforcement of breathing technique? ( photo: Neville Coleman)

Well known for their high intelligence they adapt readily to training in captivity and there are instances of them living in one locality, frolicking with swimmers, snorkellers and divers in the wild. Anybody who has seen these magnificent creatures at close range, riding the bow waves of boats or shooting the curling breakers of beach surf must in all truth realise that we as humans have a lot to answer for the hundreds of thousands we have killed in the tuna nets.