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Now You Know! Little 'n' Large - How Krill Fuel the Blue Whale
Author: Matilda Jenkins, Young Marine Biologist
Rising up from the deep, this creature is the biggest ever to exist, 10 metres longer than the ferocious megalodon. It opens its mouth, a gaping black maw, and engulfs its unfortunate meal of… plankton? Yes, the blue whale’s lunch consists of a swarm of krill, each individual around the size of your finger. These 30m long mammals and their tiny prey seem to be the ultimate contradiction, but in fact krill make a very efficient food source for these majestic whales.
🦐 Firstly, what exactly are krill? There are 85 known species of these planktonic crustaceans, which can be found in all oceans, but are most significant in the waters around Antarctica, where up to 5.5 billion tonnes of krill can be seen even from space! Krill feed on phytoplankton by migrating vertically up and down every day, helping to distribute nutrients such as iron through their waste, and they can lay up to 10,000 eggs per individual, hence their very large population sizes - family gatherings must be a nightmare.
🐋 These traits, being nutrient-rich and populous, make krill an excellent prey for the blue whale. These whales also inhabit all oceans (except the Arctic) so krill would be available to them all the time, which is especially important for their long migrations. For instance, blue whales off the American West coast migrate a massive 4,000 miles every year! The whale’s behemoth size means that it is not agile enough to be an effective hunter of faster animals, so its method of filter-feeding is much more appropriate. When a blue whale spots a swarm of krill, it lunges forward and engulfs up to 500kg of krill in one go; over the course of a day, a blue whale can consume four tonnes of krill! Check out the National Geographic video below to see these graceful giants in action.
Top predators are usually known for being fierce, ferocious hunters, but the blue whales appear to defy this vicious stereotype. Well, I guess for the krill, these whales are still a terrifying monster from the deep!
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