For the past twenty years, Jeremy Goldbogen and collaborators have been trying to figure out why blue whales were the biggest animal to ever live. The journey helped them find multiple different explanations as to why the blue whale is so unique and why it’s size is almost entirely based on two factors: their choice of prey and the coincidence of their evolution with the global increase of “upwelling of nutrient-rich water from the depths of the ocean.”
How does a Blue Whale’s diet affect its size?
Baleen Whales were able to evolve from filter-feeding on plankton to successfully lung-feeding on entire schools of fish and krill. This was a huge part of the whale’s evolution because of the ocean upwelling, which provided ample amounts of new prey for these whales.
What is specialization and how did it affect the evolution of Whales, particularly Blue Whales?
During the ocean upwelling, not all types of swarming prey were the same. As a result, predators began to become a specialist in hunting certain groups. For example, some rorquals specialized in schooling fish, while others focused on plankton. Of all the present-day rorquals, the blue whale is the most specialized. They only eat Krill with very few exceptions. Specializing in Krill is far from easy. There is only a high concentration of Krill in certain regions of the world, therefore Blue Whales need to be extremely mobile. Because of this, they have sleek bodies and hydrodynamic flippers. Krill are also not easy to catch so Blue Whales sacrifice some mobility for a more hunting range. This means a bigger mouth which comes with a bigger body. The whale’s diet depends on being big but the energy needed to maintain this big body also balances out.
The Blue Whale: Stuck between the Old and the New
The Blue Whale is in an interesting predicament when it comes to their evolution and growth. They are stuck in their circle of specialization but their food web is deteriorating across the ocean and that is where they are also stuck. As I said before, being that big takes a lot of energy. These whales needed to eat as much as possible and when we pollute the ocean that hinders their ability to do so. I believe that it is extremely important for us to do what we can as humans in order to help these creatures because right now we are living during a truly unique time: we are on the earth at the same time as giants. I believe that it is our responsibility to save them for as long as we can.