Week 1

Life History

The world’s largest living mammals swim effortlessly from the depths of the ocean, surfacing to make a stunning display that is undeniably beautiful. Whales are a part of the family known as Cetaceans (including dolphins and porpoises) that originated 50 million years ago. This family is divided into the suborders Mysticeti, marine mammals that have baleen plates instead of teeth and Odontoceti who have strong teeth. Cetacea include the largest mammals on earth and because they are mammals, we know they evolved from a land-dwelling ancestor.  This ancestor however, would have looked nothing like the whales we see today.

Fun Fact! Orcas, often called ‘Killer Whales’ are actually the largest species of dolphin.

Sixty-six million years ago the Cretaceous-Paleogene extinction event wiped out nearly three quarters of the plants and animals on earth. It was 10 million year after this event and 250 million years after the first tetrapod -vertebrate with arms and legs- crawled out of the ocean and onto land, that the first whale evolved. This ancestral tetrapod went back to the ocean! Paleontologists have been able to construct a fossil record that demonstrates the ancestral mammal’s transition from land back to the ocean. This transition remains the best example of macroevolution documented in the fossil record. Macroevolution describes evolutionary patterns that span above the species level on the tree of life, and occur over vast periods of time. For me it is unclear why the cetaceans moved back to the oceans. Maybe it was resource availability or to escape a predator.

Since cetaceans originated from land mammals there are several features scientists have observed that are shared amongst land and aquatic mammals. Some general features aquatic mammals share with land mammals include nursing their young, three ear bones that are involved in sound transmission (hammer, anvil, and stirrup), hairs on the face (sometimes whiskers) and the presence of lungs. Even though evolutionary events have altered some of these features, they remain clear signs of their mammalian heritage.

North Atlantic Right Whales

The species I am focusing on this month is Eubalaena glacialis, the North Atlantic Right Whales. Up until this point in my career as a marine scientist I have never learned about this species and yet they remain one of the most endangered species of whale in the world. There are only roughly 400 individuals left due to anthropogenic stressors like commercial hunting, vessel strikes, entanglement in fishing gear and climate change.

Right whales are baleen whales belonging to the family Balaenidae. This species is one of three right whale species which include the North Pacific Right Whale and Southern Right Whale. This whale species is distinguished by rough white patches on their head called callosities.

Did you know? These whales gather small organisms near the surface to eat, however their buoyancy and this feeding behavior leaves them vulnerable to collisions.

These stocky, black-bodied individuals are baleen whales, feeding on copepods -small crustaceans just two millimeters in length- and other zooplankton by filtering large amounts of water through their long baleen plates. North Atlantic Right whales can be found migrating to the northern Atlantic Ocean near Canada and New England to feed and mate. In the Fall, the whales will travel thousands of miles south, as far as northeastern Florida where females give birth.

Thank you for reading my very first blog post! Please stay tuned, in the following weeks I will continue with my research about North Atlantic Right Whale’s conservation status (including tips on what you can do to help) and discuss novel relevant research.

References