The Toothed Cetaceans and Their Current Situation

Order cetacean, which is the largest order of marine mammals, has two suborders, one is mysteceti, which is the order of baleen whales and another one is odontoceti, which is the suborder containing toothed whales. This suborder also includes dolphins and porpoises. There are several differences between baleen whales and toothed whales. The most important among them, as the name itself indicates, toothed whales have teeth whereas baleen whales have baleens, which help them to filter feed krill’s and other small organisms. Toothed whales are usually smaller compared to baleen whales, even though sperm whale and baird’s beaked whale are exceptions. In toothed whales, males are always larger than females, whereas it is opposite in case of baleen whales. Toothed whales have only one blowhole whereas baleen whales have two blowholes.

Let us take a look at the general taxonomy of toothed whales in brief. There are about 65 species of toothed whales in total, including oceanic and river dolphins and porpoises. I am not going to mention all of them here, but mention a few important ones among them and their specialty. This suborder contains nine families. They are:

1)      Physeteridae: Sperm whale

2)      Kogiidae: Dwarf sperm whale and pygmy sperm whale

3)      Lipotidae: Baiji or Chinese River Dolphin

4)      Pontoporiidae: La Plata Dolphin

5)      Iniidae: Amazon River Dolphin

6)      Platanistidae: Gangetic Dolphin

7)      Monodontidae: Narwhal and Beluga whale

8)      Phocoenidae: Porpoises

9)      Delphinidae: Oceanic Dolphins

10)  Ziphiidae: Beaked whales

Among these nine families, Physeteridae, Iniidae (Even though its status as being monotypic family is a subject of discussion today because of the status of Bolivian River Dolphin, which will be discussed later), Lipotidae, Platanistidae and Pontoporiidae are monotypic families (Families containing a single extant species). Other five families contain different number of species. Delphinidae is the largest family of odontoceti, consisting of 38 species. More than half of the toothed whales come under this family. Common bottlenose Dolphin and killer whales (Orcas) are the best examples for the members of this family.

·         Sperm whale (Physeter catodon or Physeter macrocephalus): Sperm whales are the largest species of toothed whales. They are the only members of family Physeteridae. Males are about 50-60 feet long and can weigh up to 55 tons. Females are usually smaller, about 35-40 feet in length and weigh only half as much as males. The largest known male specimen reached a length of 67 feet and weighed more than 60 tons. Sperm whales are named after the white jelly like substance named spermaceti which is present in their huge square shaped head, which is about one third of their body length. This liquid was mistaken to be sperm in earlier days and hence this animal got its name ‘sperm whale’.

·         Killer whales (Orcinus orca): Also called orcas, killer whales actually belong to oceanic dolphin family Delphinidae and subfamily Orcininae. Even though genetically they are dolphins, they are called whales because of their large size. An adult male can reach a length of 30 feet. They are highly sociable and always move in groups containing a dozen or more whales. Their black and white appearance makes them one of the most beautiful cetaceans. They are predatory animals and they feed on seals, sea lions, dugongs, manatees and other large cetaceans. A group of killer whales sufficient in number can attack even very large whales like blue whales and fin whales also! More than half of blue whales observed near Antarctic region had scars of killer whale attacks on their bodies.

·         Narwhals (Monodon monoceros): Narwhals are members of family Monodontidae and subfamily Monodontinae. They are famous for their single tusk which protrudes from their mouth. This tusk is present only in males and it helps them while fighting for females. Even though males have a single tusk, there are some cases where they had two tusks. Two tusked males, even though less in number compared to single tusked ones, are not too rare. These whales grow to a length of 13-18 feet and weigh around 800-1600 kg (males) and 11-14 feet and 500-1000 kg in weight. Tusks of males, even though have a formidable appearance with a length exceeding 9-10 feet, are hollow and weigh only 8-10 kg.

·         Beluga whale (Delphinapterus leucas): Beluga whales are also called white whales, because of their beautiful milky white appearance. They belong to family Monodontidae, subfamily Delphinapterinae. They are about the same size of narwhals. Difference is that they don’t have tusk and are pure white in color, contrary to bluish black color of narwhals.

·         Baiji or Chinese river Dolphin (Lipotes vexillifer) : Baiji, which is the only member of family Lipotidae, is an example of how human interruption with nature can destroy a large animal and lead it to complete extinction. Since 2006, no individual was sighted in any part of china and it has been declared as functionally extinct. Extinction of this wonderful Dolphin is a result of excessive fishing, hydro electricity generation and other human activities in rivers. In august 2007, a Chinese man reported that he saw a very large white animal swimming in a river, but his video was too blurred to identify that animal.

·         Gangetic river dolphin (Platenista gangetica) : There are two subspecies of Gangetic river Dolphins, namely Gangetic river Dolphins (Platenista gangetica gangetica) and Indus River Dolphins (Platenista gangetica minor). They belong to family Platanistidae. These are the only dolphins which are found in Indian rivers. They are also called blind river dolphins, because their eyes are almost vestigial and they are covered by a membrane of skin. They are also called south Asian river dolphins.

·         Amazon River Dolphin (Inia geoffrensis) : This Dolphin is found in Amazon, world’s largest river. They belong to family Iniidae. There are two recognized subspecies, namely Amazon River Dolphin (Inia geoffrensis geoffrensis)  and Bolivian River Dolphin (Inia geoffrensis boliviensis), but today they are being treated as two separate species. Even though it is so, some taxonomists still consider Bolivian River Dolphin as a subspecies of Amazon River Dolphin.

·         Pilot whales: There are two species of pilot whales, which belong to family Delphinidae, subfamily Orcininae and genus Globicephala. Long finned pilot whale (Globicephala melas) and short finned pilot wahle (Globicephala macrorhyncus) are almost similar in their appearance except their fins, which are long and short respectively, as the name itself indicates. Adults can grow 3.5-6.5 meters long and can weigh about 1-4 tons.

·         Porpoises: Porpoises are members of family Phocoenidae. They are very small in size and range from 5-8 feet in length and weigh between 30-200 kg. They are the smallest group of cetaceans. Even though they look similar to dolphins, they are distinguished from Dolphins by their shorter and flattened beaks and teeth which are spade shaped, which are different from conical teeth of dolphins. Word ‘porpoise’ actually means ‘small dolphin’. There are six species of porpoises in three genera.

Unfortunately, none of these wonderful creatures are safe today. They are being killed by man for several reasons. Whether knowingly or unknowingly, we are all being responsible for the destruction of these animals by our various activities. Baiji is an example only and it is not the first and surely will not be the last animal to pay for the greed of human beings. Let us save at least the remaining species with care and let our younger generation also see these animals and admire wonders of nature!