The Biggest Mouthful: How Blue Whales Eat and Why Krill Matters

A blue whale can swallow a volume of water bigger than its own body in a single gulp. That move, called lunge feeding, is one of the most extreme feats in the animal kingdom, and it only pays off when krill is packed into thick, dense swarms. In a thin patch, a blue whale gets back about six times the energy it spent. In a dense swarm, it gets back more than 200 times.

In this first episode of the Age of Giants series, Andrew breaks down how rorqual whales feed, then follows the krill. In 2025, the Antarctic krill fishery hit its 620,000 tonne precautionary limit for the first time and closed months early, with catches concentrated in the same Antarctic Peninsula waters where whales feed. Andrew also explains the "krill paradox": scientists now know whales eat about three times more than older estimates, and their iron-rich poop fertilizes the plankton that krill depend on. Whales help grow the very swarms they eat.

The episode closes on South Georgia, where whalers killed 42,698 blue whales and surveys recorded one sighting in twenty years. In 2020, researchers counted 58 blue whale sightings in three weeks. Andrew shares one simple action you can take today to keep more krill in the ocean for whales.

Takeaways

• Rorqual whales (blue, fin, humpback) feed by lunging, expanding pleated throats to engulf huge volumes of water and prey.
• A single blue whale lunge costs roughly 3,000 to 8,000 kilojoules, so lunge feeding only works on dense krill swarms.
• A feeding blue whale in the eastern North Pacific can eat about 16 tonnes of krill a day.
• The Antarctic krill fishery reached its 620,000 tonne trigger level for the first time in 2025 and closed early.
• Whales recycle iron that fuels plankton growth; Southern Ocean whales recycle about one tenth of the iron they did before whaling.
• Blue whales are returning to South Georgia after being hunted out locally, about 50 years after whaling ended there.
• Action: skip krill oil and choose an algae-based omega-3 supplement.

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