Whales & Dolphins – Cetacea


First of all I have to mention: Dolphins are whales as well!

Whales (Cetacea) are an infraorder in the class of mammals that contains about 90 species. The dolphins (Delphinidae) are a family in the infraorder order of whales.

Cetaceans are separated into two parvorders. Beside the Baleen Whales (Mysticeti), which feed mainly by filtering plankton and schools of small fish, there are the predatory-living Tooth Whales (Odontoceti), which include dolphins.

Around the Canary Islands there are 27 different species of whales and dolphins, which is a lot, compared to other regions. When diving, they are unfortunately very rare, because the direct approach, in order to dive with the marine mammals is forbidden. Snorkeling is forbidden as well to protect the animals. You will need some luck and that one of them is passing by during a dive..

This is, however, no reason to give up. Instead one can go on a boat trip with one of the many Whale Watching operators. The chance to see dolphins or whales is about 95%. In addition, some offer a free repeat trip, when all the whales have just dived.

Species of Whales and Dolphins on the Canaries

Anatomy

Externally, the whales look quiet similar to the fishes, which is due to the special conditions of their habitat. However, cetaceans are not fish, but mammals, which is evident from the following essential features:

  • They are air breathing and have lungs
  • Whales have a particularly powerful heart, whereby oxygen is distributed very effectively in the body
  • They are homeotherm animals and maintain a constant temperature, independent of the environment
  • Whales bear fully developed calves, nurture them with fat-rich mother’s milk, the embryonic development takes place in the mother’s body and during this time the embryo feeds through special nutrient tissue (placenta)

 

External Anatomy

External Anatomy whales cetacea dolphins cetaceans melon blow hole flipper fluke dorsal fin example ocean explorer la palma
Outer anatomy of whales by the example of a dolphin.
Original Photo: Ocean Explorer La Palma

In general, cetaceans have a streamlined physique.

Their anterior extremities are reshaped to fins (Flipper). Furthermore most whales have an additional dorsal fin on their backs, and a cartilaginous tail fin (Fluke) at the posterior end. In contrast to the fishes, this is horizontal with cetaceans. Flipper and dorsal fin only serve for stabilisation in the water, while the Fluke is used for the drive.

The blow hole represents the nostrils. While the baleen whales have two of them, tooth whales have only one.

In addition, tooth whales have a head arch, called the melon. It is filled with air bags and fat, which in except of the buoyancy also supports the creation of sounds.

Internal Anatomy

Under the skin, the body of the whales is wrapped by a thick layer of speck (blubber), which can grow up to a half a meter in large species.

Since their skeleton is supported by the water, they almost go without compact bones. Moreover, the compact bones commonly used in mammalian animals are replaced by fine-meshed cancellous bone, which are lighter and more elastic. Some bone elements are even replaced by cartilage or adipose tissue. Furthermore, in the ears and snout of the cetaceans, there are bones of very high density, which do not occur in any other animal. As a result, these better acoustic properties and the sounds are better conducted.

A highly efficient respiratory and circulatory system allows Cetacea to store enough oxygen for their dives. Finally, they can exchange up to 90% of the air volume of their lungs with each breath. The oxygen is stored, except in the blood and lungs, also in the musculature. Depending on the species, whales can dive up to two hours and reach depths greater than 3000m.

The kidneys of the whales consist of several thousand single lobes. This allows them to work more efficiently. The kidneys also serve for the salt excretion, which allows the cetaceans to drink salt water.

Habitat and Distribution

Whales are the only mammals that are not able to survive outside the water besides the sea cows. They are found all over the world in all seas. Many species of different families, also known as river dolphins, also live in rivers or estuaries. There are species that are distributed all around the world, such as blue whales or humpback whales, as well as species that occur only locally, such as the Vaquita or Hector’s dolphin. There are both cetaceans, which favour deeper marine regions, as well as those that are more likely to be in coastal regions.

Social Behaviour

Typically, whales are social animals with a highly developed social behaviour. The fewest species live in pairs or as loners. Whale schools consist of up to 50 animals, some events can even bring more than 1000 animals together. It is quite possible that it comes to the socialization between different whale species.

Individual schools have a fixed hierarchy. Mutual body contact is just as important as playing with waves or jumping. In addition, whales communicate much about their singing, which can be heard several hundred kilometres in some species.

Reproduction

The majority of all cetaceans have a seasonal reproduction cycle, which is linked to seasonal migrations. Whilst tooth whales do not form a fixed bond, baleen whales are usually monogamous during a breeding season. The gestation period lasts between 9 and 16 months and is not necessarily dependent on the size of the whale.

Systematik / Taxonomie der Wale

In the classical system, the cetaceans are divided into two parvorders.

Firstly, there is the parvorder of baleen whales. They do not have any teeth in her mouth. Instead, they have baleens with which they filter the water to feed on plankton and small fish.

Secondly there are the tooth whales, which as their name already reveals, are characterized by the teeth in their mouth. They live predatorily and feed mainly on cephalopods, fishes and crustaceans.

Sources & Links

Fotos

Ocean Explorer La Palma: Blainville’s Beaked Whale

http://canariasconservacion.org/: Fin Whale, Striped Dolphin, Fraser’s Dolphin, Common Bootlenose Dolphin

Internet

https://de.wikipedia.org/

https://en.wikipedia.org/