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).
The image to below shows a tooth (from a sperm whale) on the left and a baleen plate on the right.
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.
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)
Baleen plates hanging from the top jaw (Sei whale)
In this photo you can see the two blowholes (Fin whale)
Good view of the throat pleats (Sei whale)
A swarm of krill (baleen whale food) just beneath the surface
Baleen whale poo - the colour is a result of the orange-red krill they feed on
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.
- macrocephalus (Sperm whale/Cachalot)
- breviceps (Pygmy sperm whale)
- sima (Dwarf 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)
Single blowhole (Common dolphin)
Two sperm whales showing the location of their single blowhole (situated on the front left of their head)
Sperm whale surfacing, showing the lower jaw (where the teeth are situated)
Sperm whale with it's mouth open, showing the sockets in the upper jaw (where its teeth fit into)
Another view of the teeth sockets of a sperm whale (seen together with a bottlenose dolphin)
Blainville's beaked whale, showing two tusk-like teeth protruding up from the lower jaw
Logging is when a cetacean is resting at the surface with just its back visible at the surface - looking much like a floating log in the water. This behaviour is typical for the sperm whale, kogiids, pilot whales, orcas and narwhals.
Sperm whales logging
Pilot whale logging
Bowriding is a behaviour we see in many dolphin species, like common, spotted and bottlenose dolphins. They ride on the wave that the boat creates at the bow, taking a free ride. But we have also seen other dolphin species bowride such as false killer whale and Risso's dolphin.
Side view of common dolphins bowriding our catamaran
Bowriding, view from underwater, of our zodiac
Fluking (also known sounding) is when a cetacean dives and shows its fluke/tail above the water. Its typical of the sperm whale when they are going on a deep dive. This is a perfect opportunity for the biologists to take ID photos of the whales.
Lobtailing is different from fluking the whale or dolphins is not diving. Rather it is lifting the fluke/tail high in the air and slapping its on the surface, often repeatedly. It can be for fun and play, getting rid of parasites, communication or irritation.
When a whale breaches it leaps almost clear out of the water and lands, often on its side or on its back, with a huge splash. Breaching is thought to have several functions including a form of communicating with other individuals nearby, removing old skin and parasites and even dislodging blockages from their bowels. Breaching is a behaviour displayed by only some whale species (common examples being humpback whales, sperm whales and right whales). It is rare to see a baleen whale, especially the larger species, breach.
Many dolphin species jump or leap, often very high so that the whole body comes out of the water. These jumps can be a way of travelling, a way of communicating with other individuals (especially as courtship behaviour during mating activity), a way for the young ones to learn coordination skills, spying on us humans on the boats or simply a way for the dolphins to have fun.
Bottlenose leaping very high
Spotted dolphin jumping
Spyhopping is when a cetacean lifts its head out of the water. They may do this to see what is above, checking out the surroundings to see surface movements like other individuals jumping or groups of birds, or just spying on us humans.
Humpback whale spyhopping
Pilot whale spyhopping
Pectoral fin slapping
Pectoral fin slapping is when a cetacean slaps its pectoral fins (the fins at their sides, equivalent to our arms) on the surface of the water, often repeatedly. It is most common to see this in humpback whales (their pectoral fins can reach up to 6 m in length!) but can also be observed in other species.
Blue whale pectoral fin slapping (extremely rare for this species!)
Humpback whales showing its huge pectoral fin
Orca (killer whale) lying on its back showing both pectoral fins
Many dolphins taken advantage of the power of the waves to surf, maybe as an energy efficient way of travelling, or maybe just for fun. It sure looks fun!
Common dolphins surfing in the natural waves
Common dolphins surfing in the waves created by our catamaran
Running is a behaviour we see with dolphins, very typical for striped dolphins, but also spotted and common. Its a way of travelling very fast constantly leaping out of the water to get more speed.