Cetaceans

Haviside’s Dolphin (Cephalorhynchus heavisidii)

Haviside’s dolphin is small dolphin which is found solely off the coast of Namibia and the west coast of South Africa. Little is known about the species, although, much has been learnt about the behaviour of the dolphin in recent years.  It is very active at the surface and often approaches boats to wake- or bow-ride. It breaches frequently, somersaults and may porpoise at high speed.

The beaked whales are the least known of all cetaceans, some have never even been seen alive. There are 21 known species, most of them are known from studying dead animals which have been washed ashore, and some from being briefly observed at sea.

The reason why we know so little about these whales is because they live far out at sea and at great depths. They dive for long periods of time, sometimes as long as 85 minutes, to depths of more than 1900 meters. The beaked whales are thought to spend much of their lives below the surface and they are well adapted to their deep sea habitat, having larger spleens and livers than most cetaceans.
Beaked whales are very widespread and can be found from the North to the South Pole and anywhere in between. They’re generally found off the edge of continental shelves, around seamounts, canyons and escarpments.

The sizes of the different species vary from the smallest member of the family, Lesser beaked whale (up to 3,7m) to the largest, Baird’s beaked whale (growing as long as 12,8m).

All of the different species have elongated snouts, beaks, which make them somewhat similar to dolphins.The beaked whales are the only species among toothed whales which only have one pair of teeth (a few species have two pairs while Gray’s and Shepherd’s beaked whales have rows of tiny teeth). The teeth are thought to be used when males compete for the favour of females. In females, the teeth do not erupt but remain hidden. The male’s teeth make the beaked whales the only marine mammals whose evolution has been shaped by a secondary sexual characteristic.

Beaked whales feed using suction feeding, meaning they suck their prey into their oral cavities. The preferred diet is deep-water squid, benthic and benthopelagic fish and some crustaceans.

Blainville’s beaked whales

Sowerby’s beaked whale

Blainville’s beaked whale

Hector’s beaked whale

Blainville’s beaked whale

Irrawaddy Dolphin (Orcaella brevirostris)

The Irrawaddy dolphin is a euryhaline species, meaning it can to adapt to a wide range of salinities, sweet as well as salt water. It is found in shallow coastal waters of the tropical Indo-Pacific and in large river systems such as Brahmaputra, Ganges, Mekong, Mahakam and Irrawaddy. Only a few years ago, in 2005, a second species in its genus was recognised, The Australian Snubfin dolphin which is found at the coastlines of northern Australia. The Irrawaddy dolphin’s appearance is similar to the Beluga, but it is most closely related to the Orca.