With 170 tons, the equivalent of 25 elephants combined, the blue whale is the largest animal on earth. And yet it has not always been so, what has happened? The scientists give us the reasons. To reconstruct the evolution of the marine mammal, they examined the fossilized skulls of 63 species of whales no longer existing, and 13 still existing. This study showed that a gradual change took place 4.5 million years ago. A recent gigantism. The whales were only about 10 meters tall, 2 to 3 million years ago, so their gigantism is recent. As Graham Slater, a biologist who participated in the research, explains, “if we look at their 36-million-year-long history, they were only giant for one-tenth of that time.”
The impact of climate on whale size
The advent of a glacial era would be at the origin of these transformations. The cooling of the waters, by modifying the ocean currents, put an end to the uniform distribution of the plankton. For feeding, whales had to travel farther distances. Increasing their size would have been the solution to adapt to this change of life. The decline in water temperatures also brought to the surface the living nutrients that were deep down in the depths. The cetaceans then had at their disposal, food in abundance. And as Graham Slater says “the bigger your mouth, the more you can absorb by spending a minimum of energy”. And the bigger the whales, the more likely they were to survive the long migrations, it was their only way to survive ! Discover also the 10 biggest fish in the world.
