Content on this page requires a newer version of Adobe Flash Player.

Get Adobe Flash player

 

Search in the Encyclopedia

Cetaceans

breathing method:

via lungs, stores oxygen in muscles

size and weight:/

largest cetacean (blue whale): maximum 33 meters and 170,000 kilograms
smallest cetacean (porpoise):  maximum 1.90 meters and 60 kilograms

communication:

baleen whales low-frequency sounds
toothed whales echolocation

enemies:

humans (hunting, pollution, noise pollution) and diseases

food:

baleen whales small marine animals, plankton and small shellfish
toothed whales fish, cuttlefish

  • Dut: walvisachtigen
  • Eng: cetaceans (whales, dolphins, porpoises)
  • Fren: cétacés (baleines et dauphins)
  • Ger: Walartige
  • Lat: Cetacea
  • Dan: Cetacean
, Most drawings: Frits Jan Maas

Cetaceans

Cetaceans is the official name for the whale family. When you hear the word 'whale', you usually picture a giant animal. However, porpoises which are only 1.5 meters long also fall under cetaceans. The predecessors of the cetaceans lived on land. During the Tertiary period (around 50 million years ago), a group of predator-like mammals moved to coastal regions. They slowly adapted to swimming in the sea. They were animals without back legs, but had fins and a wide flattened tail.

  • Teeth or seaves
    Killer whale, marijke de boer

    Cetaceans can be subdivided into baleen whales and toothed whales. Most baleen whales are gigantic. They have an enormous toothless mouth. Instead of teeth they have baleen plates, which are made from horn-like material and hang in rows in the palate of the upper jaw. The whales use these baleen plates to filter out their food. Most of these whales live off of krill: shrimp-like animals found in plentiful amounts in the open sea. They will also consume small fish such as herring.

    Toothed whales are generally much smaller than baleen whales. Only sperm whales are comparable in length with baleen whales. Dolphins and porpoises are also toothed whales. They eat primarily fish or squid. The killer whale also hunts seals, penguins, sharks, porpoises and dolphins.

  • Distribution in the North Sea
    Sperm whales, marijke de boer

    Cetaceans are difficult to spot because they usually swim deep under the surface. Large whales are rare in the North Sea. Only the minke whale, the smallest baleen whale, is regularly seen in the northern half of the North Sea. In recent years, since the millennium, humpback whales have also been spotted regularly off the Dutch coast. These animals seem capable of swimming in shallower waters, particularly when hunting large schools of fish. If a sperm whale or any other large whale species ends up in the shallow southern North Sea, then it is usually a case of a vagrant; animals that have left their natural environment for an unknown reason. Their chances of survival are slight and they usually eventually wash ashore somewhere. Due to climate change, the currents in the ocean are changing. It is quite possible that more whales and more species of whales will find their way to the North Sea.

  • Dolphin rehabilitation
    porpoise on Texel, ecomare, salko de wolf

    Live large whales that wash ashore are difficult to rescue. They are too large and too heavy and collapse under their own weight. There is only a chance of helping them after stranding if they can float during the following flood. Specialist can then try to lead them to deeper waters. Porpoises and dolphins are easier to rescue but even these animals are much more difficult to care for than seals. The organization SOS Dolphin, located at the Dolphinarium in Hardewijk, specializes in rescuing these smaller cetaceans.

  • Exceptional cetaceans along the Dutch coast
    Beluga, Sytske Dijksen, www.fotofitis.nl

    In addition to the species mentioned above, rare whales also appear every once in awhile along the Dutch coast. Several bones have been found from the gray whale and the North Atlantic right whale not far off the coast in the North Sea. These bones are proof that these species of whales swam here probably up to the Middle Ages. Sometimes, a lost beluga from the far north is seen in the North Sea. One swam in the river Rijn in 1966. In 1980-1981 and 1984, one was seen at the mouth of the Schelde and Eems. Belugas are inhabitants of river mouths in the North Pole region. Therefore, it isn't totally strange that they were found in rivers. In 1912, a narwhal died in the Zuiderzee, another case of a vagrant from the far north. The blue whale, the pygmy sperm whale and the pair of false killer whales that once beached along the Dutch coast, had wandered in from the Atlantic Ocean.

    DatePlace and details
    1840 Blue whale - Hoek van Holland
    11 March 1912 Narwhal - Zuiderzee near Elburg
    13 December 1925 Pygmy sperm whale - Noordwijk aan Zee
    28 November 1935  False killer whale - IJmuiden, 2 animals
    From various sources, including Chris Smeenk (Naturalis)