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

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I want you to picture a blue whale,
30 meters long, 200 meters down,

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closing in on a swarm of krill so
thick it looks like a huge cloud.

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The whale beats its tail, picks up a
bunch of speed, and opens its mouth.

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In about the time it takes you to read
a text message, it swallows a volume

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of water bigger than its own body.

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And the move only pays off
when the krill is thick.

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And here's the kicker.

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The lunge move that these massive whales
do only works when the krill is thick,

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like that cloud is thick of full of krill.

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And the krill is something we're
catching more often every year as humans.

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And that's gonna be the
focus of this episode.

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And the next four episodes, we're
gonna be focusing on the biology

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of the biggest whales and what that
biology tells us about protecting them.

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And we talked yesterday with Ashley
Blawas, who is a postdoc talking

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about whales and lunge feeding and
the heart rates and everything.

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We're gonna dive deep into that in
this series for the next four episodes

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because I think it's important this week
to talk about the physiology of these

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large mammals because it's fun to know.

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And it has a little bit of,
connection with us as humans.

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So I think it's interesting
to look at that.

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And most of us, grew up with the
idea that whales were, quote-unquote

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saved, back in the 1980s when
commercial whaling was paused.

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And then you hear about ship strikes and
entanglements and climate change, and you

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start to wonder if the comeback is real
or are we gonna go on a downward trend?

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So this episode starts with the
most basic question about a giant

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whale: How does it eat enough to
have its large body stay alive?

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And once you see that answer, you see
exactly where the pressure points are

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and exactly where the good news is.

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I've spent 15 years talking to people who
study whales, and the thing that always

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gets me is how much of a whale's life
comes down to one single meal done right.

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So to understand the threat, you
first need to picture the meal.

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Blue whales, fin whales, and humpbacks
belong to a group called rorquals.

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So the word comes from the Old Norse
term of translated as furrow whale

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because of the long grooves running
down their throats and bellies.

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Those grooves are the secret.

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The skin and blubber on the rorquals
underside is pleated like an

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accordion, and it runs about half
or 60% of the whale's body length.

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When the whale opens its mouth at speed,
water rushes in and those pleats stretch

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out like a balloon filling with water.

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And a blue whale can take in
a volume of water bigger than

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its own body in a single gulp.

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Then it closes its mouth, pushes all
that water out through the baleen, the

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fringe plates, the hanging from its
upper jaw, and the water leaves, the

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krill stays, and the whale swallows.

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A scientist who modeled the energy of
a blue whale lunge found that one gulp

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cost the whale somewhere between about
3,000 and 8,000 kilojoules of energy.

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In a thin patch of krill, the whale
gets about six times what it spent.

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In a thick, dense swarm cloud, it gets
back more than 200 times what it spent.

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So the same whale, same lunge, the
only thing that changes how tightly

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the food was packed in those clouds.

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Now giant whale doesn't survive on oceans
average, it survives on finding the

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densest swarms and hitting them hard.

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They gotta eat most of that swarm.

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A blue whale in the Eastern North
Pacific can eat about 16 tons of

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krill a day when it's feeding.

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So if the whole strategy depends on dense
swarms of krill, what's the problem?

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We're gonna talk about it right now.

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Antarctic krill are small
shrimp-like animals about half

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the length of your finger.

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They gather in swarms so dense that
they can tint the water, and they

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feed penguins, seals, fish, seabirds,
and the biggest whales on earth.

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They also feed an industry.

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So the fishing vessels in the Southern
Ocean catch krill for omega-3 supplements

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for feed on salmon farms and for pet food.

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The international body that manages
the fishery is the Commission for

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the Conservation of Antarctic Marine
Living Resources, or the CCAMLR.

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It's a lot to say.

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And it set a precautionary
ceiling back in 1991.

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It's called the trigger level,
so 620,000 of tons a year.

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That's as much as they can catch.

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And for more than three decades,
the fisheries never reached it.

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But in 2005 it did.

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The fleet hit 620,000 tons by early
August, and the season closed months ahead

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of the schedule for the first time ever.

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This total isn't only a concern.

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A rule that spread the catch out
across areas lapsed the year before.

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So in waters in the Antarctic Peninsula,
the catches went past 355,000 tons, more

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than double the old limit for that area.

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These are the same waters where
humpbacks and other whales come to feed.

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Phil Trathan, a longtime Antarctic
ecosystem scientist, pointed out

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that the commission does not have any
mechanism in place to monitor baleen

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whales even though whales likely eat more
krill in that area than anything else.

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Now a fishing fleet goes where krill
is densest, and so does a lunge feeder.

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They are hunting in the same exact swarms.

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Now, the industry says the closure
shows the system is working as designed.

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They have a quota, they met
that quota, they shut it down.

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And both things can be true.

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The limit held and the limit
was set before anyone knew

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how much whales could eat.

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I wanna talk about something that
scientists figured out that changes

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the thinking about all this.

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In the 20th century, industrial
whaling killed somewhere between

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two and three million whales with
most of the krill eaters gone.

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So people expected the Southern Ocean
to fill up with krill, but it didn't.

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Krill numbers seemed to fall instead.

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In 2021, a team of scientists put
tags on 321 whales and measured

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how much they actually eat.

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They found baleen whales eat about
three times more than older estimates.

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And when whales eat,

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they also poop near the surface, where it
could act as fertilizers for the ocean.

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Whale poop is rich in iron, and iron
is the nutrient that limits plankton

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growth in much of the Southern Ocean.

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So before whaling, the team estimated
Southern Ocean whales recycled

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about 12,000 tons of iron a year.

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Today, it's around 1,200 tons,
about one tenth of that amount.

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More plankton means more krill.

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More krill means more food for whales.

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The whales were helping grow the
very swarms that they actually ate.

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Nicholas Pyenson, a Smithsonian
scientist on this study, put it this

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way: "If we restore whale populations
to pre-whaling levels, we'll restore the

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huge amount of lost function to the ocean.

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Whales play a more important
role than we actually think.

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They help farm their own food.

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That's the strongest reason to
protect swarms they feed on.

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Now here's an example.

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South Georgia is a remote
island in the South Atlantic,

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east of the Falkland Islands.

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In the early 1900s, its waters
were full of blue whales,

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these massive, massive animals.

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So whaling stations of course,
were built on its shores.

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Between 1904 and 1971, whalers killed
42,698 blue whales off South Georgia.

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Most of them died before the mid-1930s.

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By the end, the blue whales were gone.

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From 1998 to 2018, survey after
survey recorded exactly one blue

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whale sighting in those waters.

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Scientists began to treat South Georgia
as the textbook case of a population

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hunted past the point of return.

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The lead author of a later study,
Susanna Calderon, described it as an

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iconic example of a population that
was locally exploited beyond recovery.

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Then, in February 2020, a
research team went back.

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In three weeks of surveys, they
recorded 58 blue whale sightings.

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Their underwater microphones picked
up blue whale calls again and again.

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And then they compared photos of 41
blue whales seen around South Georgia

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over the previous decade with a catalog
of 517 known Antarctic blue whales.

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None of them matched.

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These were new whales finding their
way back to feeding grounds their

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species had used for thousands of years.

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Now, the return took about 50 years
after the last whaling station closed.

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And it's because whales are slow
to recover, and they do recover

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when they have food and space.

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But you gotta remember,
these are large animals.

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They don't just reproduce like
fish, where, they put out, like,

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millions of eggs, and then, those
get fertilized, they get a higher

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fecundity, so higher reproduction rate.

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These whales will, give birth to calves.

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Those calves have to reach sexual
maturity, which takes a long time.

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They will reproduce.

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And it takes a long time for
these whales to recover because

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of their slow life history.

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Antarctic blue whale populations are still
a small fraction of what they once were.

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And the krill fishery is
legal and is regulated.

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The question is now is whether
the rules keep up with what we

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know about how much whales eat.

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And this is not just the fact
of these fishers are taking away

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the krill cause of the whales.

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It's the fact of, hey, we know these
whales actually will produce more krill.

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When we now know that these
whales will produce the food that

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will help the krill survive, and
that will help grow the krill.

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We keep taking the krill, and
we don't allow the whales to

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recover, then that whole loop, that
feedback loop just gets destroyed,

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And the fact is, like, we don't just have
a lack of blue whales happening here.

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We have other things that are happening.

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Krill face warming seas, shrinking
sea ice which young krill rely

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on, and the whales can't afford
to share the shrinking pantry.

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So the fact is, is your call to action
for this episode is skip the krill oil.

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If you take an omega-3 supplement,
choose one that's made from algae.

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Fish get their omega-3s from eating
algae in the first place, so algal-based

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supplements go straight to the source.

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If you start to think about how you can
get and how you can save the planet, is

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get away from those types of omega-3 fatty
acids and go towards the algae-based ones.

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It's just the same.

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You won't even taste the difference, and
you'll still get your omega-3 fatty acids.

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Now every capsule of krill
oil starts as a krill swarm.

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That swarm is, same dense patch a blue
whale needs to make its lunge pay off.

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Most of the krill catch goes to farm
fish feed, which is harder for one

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person to change, but the supplement
aisle is the piece you control directly,

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you can do that even today.

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Next time you buy that supplement,
Go towards that algae-based

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instead of animal-based.

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So you think about it, in South
Georgia we had one sighting in 20

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years, then we had 58 in three weeks.

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These blue whales will recover
if we give them time and we

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get them to have their food.

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Them having their food equals more krill
in the long run, blue whales, lunging

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into krill swarms in the same waters
where their species was nearly erased.

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This is what is important.

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They almost got hunted to extinction.

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The recovery takes a little bit longer.

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Krill swarms are going down 'cause
we are trying to catch them more.

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We have a quota, but the thing is, is now
that the blue whales have been gone, it

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has been harder to reproduce those krill.

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They have no food provided for
the phytoplankton, which the

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phytoplankton is food for the krill.

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So the biggest animal that ever lived
only needs two things to come back.

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They need room to swim and a
swarm worth opening its mouth for.

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That's really what it comes down to.

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Now that's the episode for today.

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Tomorrow we're gonna follow that
whale down a dive and listen to

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its heartbeat, it does something
that no human heart could survive.

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We're gonna talk about
that on next episode.

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But until then, if you have a question
about this episode and you're listening

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to it on Spotify, hit me in the comments.

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I would love to hear about that.

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I check those all the time.

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As soon as I get a comment, I get
an alert, so I'd love to chat back.

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And of course, if you're listening to
this on your favorite podcast app that

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doesn't allow comments, which is too
bad 'cause I really like that feedback

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area, you can hit me up on my socials.

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The links are in the show notes.

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I wanna thank you for watching
this episode of the How to

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Protect the Ocean podcast.

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I'm your host, Andrew Lewin.

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Have a great day.

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We'll talk to you tomorrow,
and happy conservation.