What is a cetacean?
Cetaceans are whales, dolphins and porpoises. Cetaceans are mammals which means they breathe air, give birth to live young (underwater unlike seals who give birth on land) and suckle their calves. The closest relatives of the cetaceans are the ‘artiodactyls’, an order of even-toed ungulates (hoofed mammals) that include the hippopotamus, camel and giraffe. There are currently around 86 recognised species which can be divided into two suborders: toothed whales (odontocetes) and baleen whales (mysticetes).
Toothed whales and baleen whales
Toothed whales (Odontocetes)
As the name indicates, toothed whales have teeth, which vary in size, form and number between species. Some are actually toothless as the teeth stay buried in the gums or jaws throughout the animal’s lifetime. Toothed whales hunt different types of prey including fish, squids, crustaceans, birds and even other marine mammals.
Baleen whale (Mysticetes)
Instead of teeth, baleen whales have fibrous plates (called baleen plates) hanging from their top jaw. These plates are made from keratin (the same protein that our hair and fingernails are made from) and vary in size, number and colouration between species. These plates filter small organisms out of the water, such as krill and other plankton and small schooling fish (for example herring, sardines and mackerel). Baleen whales capture their food using different techniques such as gulp-feeding, skim-feeding, bubble net feeding and bottom-feeding.
More about baleen whales
All baleen whales have two blowholes, symmetrical skulls and only one sternum bone (breastbone). For most baleen whale species the females is larger than the male. The queen of the oceans is the blue whale. The largest recorded blue whale was a female reaching 33 m in length.
The baleen whale suborder includes 17 species which are listed below:
Rorquals (6 of 11 species recorded in Azores)
– musculus (Blue whale)
– physalus (Fin whale)
– borealis (Sei whale)
– acutorostrata (Minke whale)
– edeni (Bryde’s whale)
– novaeangliae (Humpback whale)
Grey whale (1 species, not seen in the Azores)
Right whales (3 species, not seen in the Azores)
The Northatlantic right whale have been sighted in Azorean waters
Pygmy right whale (1 species, not seen in the Azores)
Bowhead whale (1 species, not seen in the Azores)
More about toothed whales
All toothed whales have a single blowhole, an asymmetrical skull, three sternum bones and an organ in the forehead called the ‘melon’ which is used for echolocation.
Sexual dimorphism is not unusual among cetaceans, with the male often being larger than the female. This size difference is the most extreme in sperm whales. The female sperm whale is about 1/3 smaller and only half the weight of the male sperm whale.
The toothed whale suborder includes 71 species and you will see a short presentation of them below:
– macrocephalus (Sperm whale)
Oceanic dolphins (10 of 35 species recorded in Azores)
Tursiops– truncatus (Bottlenose dolphin)
Delphinus– delphis (Common dolphin)
Grampus– griseus (Risso’s dolphin)
Stenella– frontalis (Atlantic spotted dolphin)
– coeruleoalba (Striped dolphin)
Globicephala (Pilot ssp.)
– macrorhynchus (Shortfinned pilot whale)
– melas (Longfinned pilot whale)
– crassidens (False killer whale)
– orca (Orca/killer whale)
– bredanensis (Rough-toothed dolphin)
Beaked whales (6 of 21 species recorded in Azores)
– bidens (Sowerby’s beaked whale)
– densirostris (Blainville’s beaked whale)
– europaeus (Gervais’ beaked whale)
– mirus (True’s beaked whale)
– cavirostris (Cuvier’s beaked whale)
– ampullatus (Northern bottlenose whale)
Porpoises (6 species, not seen in the Azores)
River dolphins (4 species, not seen in the Azores)
Beluga and narwhal (2 species, not seen in the Azores)