Dolphin sightings in waters around our islands are welcomed as happy, auspicious signs. Highly intelligent and playful, they inhabit or traverse waters around the world and they need our protection. Dr Anjani Ganase provides some facts about these marine mammals.
Their diversity
Did you know that killer whales, false killer whales and melon-head whales are dolphins? All are members of the family Delphinidae. There are 42 species of dolphins found all over the world. They roam the open ocean and dolphin species are found in all the oceans and seas with a few exceptions. While most prefer warmer tropical waters, there are a few species, such as the orcas, that travel to the polar regions. Orcas have even been encountered along the north coast of Trinidad.
[caption id="attachment_911919" align="alignnone" width="1024"] An orca, Skjervøy, Norway. PHOTO BY Toby Matthews/Ocean Image Bank -[/caption]
Their sizes
The biggest dolphin species are the orcas or killer whales. Killer whales get up to six to eight metres in length and up to six tons. Such immense size does not keep them from swimming at speeds up to 56km/h; among the deadliest predators in the ocean. The smallest dolphin is known as Hector’s dolphin, incredibly rare as they are only found in the south Pacific along the coast of New Zealand. They have a distinct look: a blunt beak and the dorsal fin resembles a mickey mouse ear. Hector’s dolphins can weigh just over 100 lbs and get to 1.5 m in length. They tend to hunt in the coastal, turbid waters around New Zealand. A sub-species of the New Zealand dolphin is the Maui dolphin found in Hawai’i. Unfortunately, only 50 individuals of this sub species remain.
Their cousins
Dolphins and porpoises are related as they both fall under the super family of toothed whales Delphinoidea. While dolphins (Delphinidae) consist of a family of 38 ocean-dwelling species and four river species, the porpoise family (Phocoenidae) has only seven species, one of which is found in freshwater in Asia. Compared to the dolphins, porpoises are smaller in size, they don’t have such a bulbous head and lack a pronounced beak. Also, porpoises’ teeth are like spades compared to the conical teeth of dolphins. Porpoises have a shorter life span, on average 20 years. They are generally less social than dolphins, so it is unlikely that they’ll be coming around for a bow ride. One exception is the Dall’s porpoise, common to the north Pacific Ocean, which is more social. The most critically-endangered species of porpoise is the vaquita dolphins, found in a small area in the Gulf of California along the east coast of Mexico. Their populations were decimated by standing fishing nets that resulted in the decline from 600 to ten between 1996 and 2019.
River dolphins
The most peculiar dolphins are the species that are adapted to rivers. Owing to their limited range and the degree of human development along rivers, including pollution, damming and the removal of food and habitat, river dolphins are the most threatened. In the Amazon, t
