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Cetaceans - Whales, Dolphins & Porpoises... 

... or in short – cetaceans – are marine mammals that have adapted to a life exclusively in the water. In contrast to fish, they do not have gills, but breathe with lungs, like we do. That is also the reason why we can see them: because they have to come to the water surface to breathe. And that’s where we have our chance to have some amazing encounters. They give birth to live young and nurse them, and are warm blooded, just like land mammals. But because they spend most of their lives underwater, they can be really hard to find.

To move through and live in the marine environment, they have developed unique adaptations over millions of years. To propel themselves forward, their tails have turned into powerful flukes. And to direct their movements, their forearms have turned into pectoral fins or flippers, while their hind-legs have reduced almost completely. To make surfacing and breathing easier, their nostrils have moved to the top of their heads and are called blowholes.

Adaptations to a live underwater on example of a humpback whale – Christina Winkler 

25 species of cetaceans have been identified in Irish waters, many of which occur around the Iveragh peninsula. A study in 2015 concluded that common dolphins, bottlenose dolphins and minke whales are the most frequently seen cetaceans in south Kerry. If you get lucky, you might also see Risso’s dolphins, humpback whales or the much smaller harbour porpoises. Of the 28 species seen in UK waters, the Llŷn peninsula shares a few species with Iveragh: Risso’s and bottlenose dolphins, harbour porpoises and minke whales. But pilot whales can occasionally be seen also. Most cetaceans can be observed from land and from the water. However, when observing from a boat, specific guidelines must be followed to ensure the animals and passengers safety.

Mysticetes vs. Odontocetes
Differences between odontocetes and mysticetes – (IWDG)

Two fancy (scientific) words for the two categories of cetaceans (another fancy word for whales, dolphins and porpoises). These two words describe parts of the animals anatomy and how they feed: 

Mysticetes aka baleen whales

Odontocetes aka toothed whales 

  • Have baleen plates on the upper jaw only, which are made of keratin, like your fingernails 

  • Have teeth, which are mostly made of dentin, like your teeth 

  • Use baleen plates to filter huge amounts of fish and krill out of the water with one gulp 

  • Use teeth to catch single fish, squid or other marine megafauna (e.g. seals, penguins, other whales) 

  • ​May have throat pleats, which expand when filled with water and prey, and then contract to push the water out through the baleen plates  

  • Never have throat pleats, but their mouths are often elongated into beaks (as in most dolphin species)

  • ​Have two blow holes

  • ​Have one blow hole

  • ​Include the largest animals on this planet, such as blue and fin whales, the charismatic humpback whale and the minke whale, the smallest species of the baleen whales encountered on Iveragh 

  • Include all species of dolphins, orcas, belugas, pilot whales and sperm whales. Beaked whales are sometimes excluded as a completely separate group

  • ​Do not echolocate, but can produce sounds using air sacs lined along their throats to move air over vocal cords

  • Use echolocation for navigation and location of prey through an organ called melon, which is in their forehead

Surface feeding humpback whale showing throat pleats and paired blowholes – C. Winkler 

 Porpoising common dolphin showing a slender beak and one single blowhole - C. Winkler

Did you know...

… that cetaceans are conscious breathers? While our breathing is a reflex that we do not need to think about and literally can do in our sleep, cetaceans have to be awake to breathe. But how do they do that? One of the most common assumptions is that only one half of their brain sleeps at a time, while the other half stays awake and controls their breathing and is alert for possible danger. 


Additional readings:

Species - IWDG

Fluke Facts - IWDG


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