Kaikoura's resident dolphin is the dusky dolphin. The dusky dolphin (Lagenorhynchus obscurus) belongs to a group known collectively as cetaceans; this comprises all whales, dolphins and porpoises. The word cetacean is derived from the Latin cestus (a large sea animal) and the Greek ketos (sea monster).
There are currently 81 recognised species of cetacean; these comprise 11 species of baleen whales and 70 species of toothed whales, which includes all the dolphins and porpoises. The dolphin family, known as delphinidae, is made up of 33 different members.
In New Zealand the dusky dolphin is commonly found along the east coast of the South Island. Dusky dolphins are also found in other temperate waters of the world, namely the east and west coasts of southern South America, especially Argentina, off the west coast of South Africa (in the cool waters of the Benguela Current) and around the oceanic islands of Tristan de Cunha and Amsterdam Islands.
In the Kaikoura region the dusky dolphins appear year round, with a variation of movements and habits between summer and winter. In the summer months of October to April, the duskies will move in from offshore on a daily basis to the inshore waters on the southern side of the Kaikoura Peninsula. During the winter months of June to September, the duskies are located further offshore and do not normally come in as close to shore as in summer.
Maximum size is between 165cm and 195cm in New Zealand and they weigh anywhere between 60 to 90 kg in weight. The same species in South America are known to grow larger, with records of dolphins just over 2 metres in length. Life span of the dusky dolphin is thought to be anywhere between 20 to 25 years.
Dusky dolphins are very gregarious and highly social, living together in groups called pods, which in the Kaikoura region can consist of individuals numbering anywhere from 100 to 1,000 or more in a pod. In autumn and winter, pod sizes tend to be at their greatest. For this reason, Kaikoura is recognised as one of the best places in the world to regularly encounter wild dolphins in their natural state.
The dusky dolphins are reputed to be amongst the most acrobatic of the dolphin species and their spectacular leaps, jumps, side slaps and back flips, bring shouts of joy to most that go out to witness their wild and free behaviour. One of the most spectacular leaps performed by the duskies is its trademark somersault and the duskies will often repeat these acrobatic leaps time and again.
A common question we get is why do the dolphins do these leaps and jumps, to which we can only answer that in the case of the dusky dolphins, it simply reflects their exuberance and personality and as is the case with many of the animals in the wild, such behaviour is merely practicing those manoeuvres played out in more serious endeavours such as seeking out and catching prey.
Mating of dusky dolphins usually takes place during spring, summer and autumn, with not all mating being for reproductive purposes. A lot of mating is done purely as a means of socialising or maybe just for pure enjoyment. Dusky dolphins do not develop pair bonds and their mating habits could be viewed as promiscuous, with adult males competing for mating access to females. Males will pursue the female, each male often mating several times with the same female in a matter of minutes. In Kaikoura, new calves are born in the spring, anywhere from September to December after a gestation period of about 11 months.