This week Maeve delves into the world of marine mammals and takes a closer look at some of their characteristics.
Hello again whale lovers!
Another week has passed on-board DFDS Transmanche ferries between Dieppe and Newhaven. We are getting closer and closer to the end of the programme but after 11 weeks, I am still experiencing firsts! I was unable to survey on outside decks the entire week as the sea state has not gone lower than 4 and wind was accompanying the white caps… to not have a single day of good weather was definitely a first! Luckily, it’s not going to last and next week is supposed to bring better conditions. Despite this unpredicted “lock down”, passengers were present in high numbers. Following many of our conversations, I am taking this opportunity to clarify one point that was raised on several occasions; what exactly are marine mammals?
As the name suggests, they are mammals that have evolved to live and feed in the marine world. A few weeks back, I have mentioned how this evolution has taken place, but today I am going to focus more on the characteristics, and more specifically on the five that distinguish them as part of the Class Mammalia. First, they give birth to their young, after having an intra-utero gestation that can be up to 14-months for sperm whales. Cetaceans are born tail-first, and the first few weeks of their lives, they still have marks on the body due to the embryonic position they were in. Females produce milk which has a toothpaste-like consistency so that it doesn’t dissolve in the water and contains 60% fat allowing calves to grow quickly. Blue whale calves drink 450 litres per day and gain 4,5 kilograms per hour! Marine Mammals are warm-blooded animals, keeping a constant temperature of 37 degrees like us. Living in such a cold environment, they have a thick layer of fat called blubber in between the skin and the muscles/organs to avoid heat loss. Through their extremities (i.e dorsals, flippers, rostrum), they use a counter current exchange system to minimise heat loss where blood vessels entering the extremities with a temperature of 37 degrees, transfer the energy to the vessels leaving the extremities, maintaining them at a much lower temperature than the rest of the body, usually close to 10 degrees. In addition, they also breath air through lungs but unlike us, it is not an innate mechanism and they actually have to think about it. The mother has to lift her young after the birth to the surface to help him take its first breath. And last but not least, they have hairs or fur. Even whales… around their mouths, several vibrissae with hair are present to feel vibrations in the water and help locate preys.
Marine mammals have also all adaptations differently, depending on their habitats. Let’s quickly have a look at the five different orders of marine mammals. The Cetaceans are the whales, dolphins and porpoises and are completely water-dependent. The Sirenians are the herbivores of the Class, feeding on sea grass or weeds this includes animals such as the with the manatees and dugongs. The Pinnipeds have feet (hence the name) and includes seals, fur seals, sea lions and walruses. We then have the Mustelids, the sea otters from freshwater and marine habitats. And finally, we have the Ursids, which are the polar bears! Believe it or not, they are considered marine mammals as well, whereas hippos are terrestrial!
I cannot wait to tell you more about those amazing creatures, but until then, have a wonderful week and let’s hope for better conditions really soon! You have three weeks left on-board the ferries to come see me and ask all the questions regarding the marine world you want! Don’t be shy, come say hi!
ORCA Wildlife Officer – The English Channel