(background music)
The smallest marine mammal in the ocean
is still the world's biggest weasel.
Closely related to minks,
(background music)
badgers,
(background music)
and wolverines...
(background music)
...sea otters outweigh them all.
(background music)
And the largest marine mammal -
the blue whale -
(noise of whale spouting water)
is the biggest animal that the planet has ever seen.
Bigger than even the biggest dinosaur.
The tongue of a blue whale alone
weighs more than a full-grown elephant.
(background music)
And their hearts
are roughly the size of an American Bison,
(background music)
pumping about 227 liters of blood
with every single beat.
(background music)
Even the world's largest bear is a marine mammal!
(background music)
But why?
What is it about living in the ocean
that creates such behemoths?
I'm KP - a marine biologist
who specializes in marine mammals
like sea otters and walruses.
(background music)
For a long time,
scientists believed that animals in the ocean
evolved to be so massive
because of the lack of gravity.
(background music) (noise of whale spouting water)
The thinking went that the buoyancy of the water
and the ability to float made it so that
these animals didn't have to
support their weight on legs and bones.
(background music) (whale vocalizations)
Just take a look at my favorite animal of all time -
the walrus.
Walruses are incredibly graceful and agile swimmers.
They can dive up to 300 feet, or around 90 meters,
and they can reach speeds of 22 miles an hour
if they're really trying,
or 30 kilometers an hour for my metric friends.
Although their average swimming speed
is around 5 miles per hour,
or seven kilometers an hour.
But, on land...
Well, watch my boy Balzak haul out of the water.
You can see the effect gravity has on his bulk,
and the effort it takes just to lumber around.
He quite literally weighs a ton.
Like an actual ton.
Roughly 2,100 pounds, right now -
almost a thousand kilos.
And as big as he looks,
Balzak is still growing!
He's going to end up being around twice this size.
(background music)
Adult male walruses average around
4,000 to 5,000 pounds.
That's the average weight of a modern sedan,
or 40 bags of cement.
(background music)
At first glance, the theory that the lack of gravity
is why marine mammals in the ocean become so big
seems pretty plausible.
Just imagine lugging around
40 bags of cement every single day.
However, a new study by Stanford
Center for Earth, Energy, and Environmental Sciences
proved that the exact opposite is true.
It's not that living in the ocean
allows you to be a big animal,
it's that you need to be a big animal
to live in the ocean.
(background music) (noise of whale spouting water)
Or as the authors put it,
"these animals are big for very specific reasons.
It's not that they can be big, it's that they must be big."
(background music)
And the reason...
(background music)
...is body heat.
(background music)
The ocean is a cold place.
Much colder than the average
body temperature of a mammal.
And heat loss happens 27 times faster
in water than in air.
(background music)
The bigger you are, the more heat you retain.
(background music)
And when you're small,
you lose heat back into the water so fast
that the only way to generate
enough heat to stay warm
is to eat...
(background music)
...a lot.
(background music)
(background music) (water splashing sounds)
KP in clip: "Nice catch!"
(background music) (water running sounds)
Sea otters are a great example
since they're the smallest marine mammal
and the only one without a layer of blubber.
(background music) (cracking noise from otter eating crab)
While they do have the
densest fur coat in the animal kingdom,
(background music) (gentle water noise)
it isn't enough.
(background music)
Instead they generate
a massive amount of body heat
just by eating.
(background music)
Their metabolic rate, at rest,
is about three times higher
than that of a similar-sized land mammal.
(background music) (background water noise) (sea otter cracking into shell)
And every single day,
a sea otter will eat roughly
a quarter of their body weight.
So a 40 pound sea otter
will eat 10 pounds of clams, crabs, and mussels
in just one day.
Now let's compare that to a human.
We only need to eat
about two percent of our body mass every single day.
To eat as much as a sea otter,
a 150 pound person would need to eat
almost 40 quarter pound cheeseburgers
every single day.
(background music)
Blue whales tip the scale at over 300,000 pounds,
and if they needed to eat as much as a sea otter
in order to stay warm,
(background music)
(background music) (whale spouting water noise)
that would be 75,000 pounds of food in a day.
(background music)
There is simply no way for them to eat that much,
so not only have they evolved into massive creatures
that trap body heat,
but they also developed a different feeding strategy.
(background music)
Instead of teeth,
Baleen whales have plates of keratin
from which they get their name.
These baleen plates are essentially
filters inside their mouths.
When they feed,
a baleen whale opens its mouth to take in water
and then pushes the water out,
leaving the krill or whatever item they are after, inside.
(background music)
And another feeding method
that Baleen whales have adapted
to conserve their energy
is to simply rest
at the surface of the water
with their mouths open.
(background music)
Fish will actually swim inside,
seemingly mistaking it for
a safe haven from predators.
This allows Baleen whales
to expend significantly less energy on feeding
than their toothed counterparts,
like orcas and sperm whales.
(background music) (whale vocalizations)
And it allows them to grow significantly larger.
(background music)
The sperm whale seems to be the largest you can get
without a new adaptation,
the authors of the Stanford Earth study said.
The only way to get as big as a baleen whale
is to completely change how you're eating.
(background music)
Because of their massive size,
and their efficient ways of feeding,
blue whales only need to eat
about 8,500 pounds of krill a day -
(background music)
which is still the weight equivalent
of a full-grown male hippo.
(background music)
And this unfortunately means
that these whales are ingesting
an enormous amount of pollutants.
Done a video about that -
you can find it right up here.
(background music) (whale spouting water noise)
Every day, a blue whale eats
10 million pieces of microplastic.
That's a 60-inch flat-screen TV's
worth of plastic every single day.
The researchers behind this study
are now working on whether or not
their methods and findings
can explain body size distribution
in other animal groups.
(background music)
Because body size is one of the most important traits
when looking at animals.
(background music)
If you're going to measure one thing in an animal,
it should be body size,
because that one thing is related to so many others.
"If you know how big an animal is,
you probably know something
about how it moves and its metabolic rate."
(background music)
It's this information that government entities use
when designing protections
for these giant marine mammals.
And I'm speaking from experience,
as somebody who participated in
the metabolic research for juvenile walruses.
And you can find a link to that video right up here.
You can see actual footage of me
working with those walruses
around the five minute mark.
(background music)
Let me know if you have any comments
down in the section below,
and 'like and 'subscribe' if you like the video.
I'll catch you next time.
(film rolling sound effect)
Make sure your phone is on silent,
I can just see this happening.
However, a new study by Stanford
Center for Earth, Energy, and Environmental Sciences
proved that the exact opposite is true.
(background music) (water lapping noises)
(DoubleAgentXV in background: "Sounded right")
(background music) (water lapping noises)
Amazing.
(background music)
(background music) (sound of sea otter quietly munching on crab)