SNHS Biology Blog 1: Blue Whales

Emily Liu

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In “Why Are Blue Whales So Gigantic?”, Eric M. Keen delves into the big question of how whales came to be the largest living creatures in history by starting from the beginning of their evolution to their survival through specialization.

The reason why blue whales are so much larger than other species of whales begins with the processes that occurred in their ocean environment millions of years ago. The article goes in depth on the topic of the ocean upwelling as well as the advent of lunge feeding. With the new ability to consume huge amounts of prey and the subsequent influx of prey availability, whales used size to their advantage by dominating this portion of the food chain.

The article describes the process of growth due to the need for a bigger mouth to catch more prey, and thus the need for a bigger body, eventually resulting in a cycle of perpetual growth to the enormous size of blue whales today.

However, an even closer look into the species of blue whales reveals that the characteristic may be a hindrance in the marathon of species survival. Whales on average are especially large creatures, but why is it that the blue whale in particular surpasses all other whales in terms of size by a substantial margin? In fact, the second largest whale species on Earth is the Fin whale, weighing 80 tons and measuring 85 feet. The blue whale weighs 200 tons and measures upwards of 100 feet long.

The explanation for over double the weight and 20 foot extension lies once again in the processes of evolution directed at preservation of the species through time. Prey in the ocean means competition for the predator. Over time, different species of whales began to specialize in certain nutrients such as krill, plankton, schools of fish and so on. Blue whales evolved to only eat krill and little else. To consume only krill meant that whales evolved suited to long range eating and less agility, which in turn forced them to get bigger and bigger as they were outmaneuvered by other smaller whales.

The only way for blue whales to survive was to keep growing and eating more krill.

Unfortunately for this blue giant, climate change, whaling, and lack of krill abundance are significant challenges for an animal that relies solely on one food source and one function. The world favors adaptability and opportunists, but in search of survival the blue whale has locked itself in a circle of narrow specialization. It cannot evolve backwards, smaller, more nimble, more generalist. Rather, the blue whale’s size earns it the title as the largest animal in the history of planet Earth, but this outstanding feature may very well become the reason this species is isolated from adjusting to a changing environment.