All language subtitles for Natures.Strangest.Mysteries.Solved.Series.1.Part.23.Giggling.Rats.720p.HDTV.x264.AAC.MVGroup.org.eng

Narrator: Ever wondered
which animals get the giggles?

[ laughter ]

People have probably been
tickling rats

For hundreds of years
and not known that

The rats were laughing.

Narrator: What would cause
the sea lions of san francisco

To mysteriously swim
away all at once?

It's rather shocking.

And I need to ask myself why.

Why would they do that?

Narrator:
And what's made three manta rays

Synchronize their swimming?

An awful lot of what they do
is still a bit of a mystery.

Which makes them even
more magical to me.

Narrator:
Nature is awe-inspiring,

But sometimes it just
doesn't make sense.

Man: I have never seen
anything like this.

Our team of experts investigates
the weirdest animal behavior...

That's amazing.

...And the most unexpected
events...

What is causing that?

...Ever caught on camera.

My god!

These are...

Berlin, germany.

November 2016.

Scientists researching
brain development

Are conducting a study,

Tickling rats.

And the craziest thing,

Is that when rats are tickled,

They laugh!

[ high-pitched squeaking ]

That is just loopy.

But it's definitely making
some giggling noises.

[ high-pitched squeaking ]

They laugh really
really high pitched,

So you have to be listening
with a special detector

That hears in the ultrasound,
to hear the giggles.

[ high-pitched squeaking ]

Narrator: Yep, there it is.

The actual sound
of a rat laughing.

So when tickled,
the rats do laugh.

And they love it.

And we know they love it
because they actively go

For the hand to
be tickled again.

And it even goes
further than that.

There's a button
that they can press,

That if they suddenly
want to be tickled,

They can push with their nose

To let the scientists know,

"I would love a tickle
right now, please."

Narrator:
Which begs the question...

Why are some animals ticklish,
and other animals not ticklish?

♪

Narrator: To find out,
we visited humboldt university

In berlin,

Where the phenomenon
of rat giggling

Is being investigated.

We don't have a very systematic
understanding of

Which animals are ticklish.

It's clear that pretty much

All primates tested
are ticklish.

With other mammals,
it's not so clear.

One of the challenges here is to
define what a laugh is, right?

How do you know this is what
an animal's laugh sounds like?

[ laughing ]

If you look at primates, they're
making sounds that, you know...

[ mimics chimpanzee laughing ]

[ laughing ]

Not exactly human,
but close enough

That it sounds like a laugh.

Narrator: And the rat giggling

Has the same signature rhythmic,
repetitive sound.

[ high-pitched squeaking ]

Which, along with
the playful behavior,

Tells us they
really are laughing.

So how is it that some
animals are ticklish?

Could it be that they are
just more sensitive to touch?

One possibility is that
if you touch an animal,

And it feels all
that stimulation,

It's gonna laugh.

[ laughing ]

We all know that from tickling
kids, the reaction

Is pretty much involuntary.

Even when kids beg you to stop,

If you keep tickling them,
they're gonna keep laughing.

[ laughing ]

Perhaps this is just
an involuntary reaction

To being touched.

[ laughing ]

Narrator:
This meerkat is another animal

Prone to a chuckle when tickled.

[ laughing ]

♪

But michael has discovered

That when it comes to rats,

They will only laugh
under certain conditions.

Brecht: The rat needs time
to learn to be tickled.

So they need to accustom
to the experimenter.

So fearful animals
are very non-ticklish.

So for rats, it's
not just about touch.

They need to be
comfortable to laugh.

♪

So what do primates
and rats share

That might give
them the giggles?

Is it just basic intelligence?

Rats are renowned for being

Extremely smart animals
who excel at learning.

These rats have even figured
out how to play basketball.

Could it be that
intelligent animal's brains

Are just hardwired to
laugh when tickled?

While some animals might
have a sense of humor,

If you're an orangutan,

A magic trick can
be a real hoot.

This primate fell for the
oldest gag in the book.

The disappearing act.

[ laughter ]

Galante:
This amazing footage shows
animals laughing by choice.

Something that they are seeing
is disrupting their reality.

For them to be able to
process what's going on,

And realize that it's
something out of the ordinary,

And convert that into laughter,

Means you have a very smart
primate.

But rats, while
being intelligent,

Might not be smart
enough to get a joke

Like our primate friends.

So why are they laughing,

Even when they're
not being tickled?

I think the key to
understand where this

Laughter stuff comes from,

Is that you only see this
laughing and this tickling,

In social species.

So laughter might be
really about communication.

♪

There's further
evidence that laughter

Is all about social stuff.

For one thing,
if you look at humans,

We are 30 times
more likely to laugh

If we're around other people.

Narrator: And scientists think
laughing might be how animals

That live in groups
encourage play and learning.

The most intelligent animals
are social beings.

They're mammals with
an immense mental ability.

All of the animals have
an advanced social structure,

And playing is a big part
of learning for them.

Michael's work tickling rats
confirms this theory.

Brecht: We think ticklishness
and the vocalizations,

Is something that makes
it fun for animals

And humans to interact.

So it is something
that encourages

The playful interaction.

It's really a trick

That gets animals or humans
together.

Schreiber: So scientists
think that the reason

The rats enjoy being tickled,

Is because it's helping them
to learn to be more social.

Narrator: And why does
this research matter?

Schreiber:
We're taking this knowledge
and applying it to humans.

We're showing that if you
do play with a young child

More and more when
they're younger,

It is gonna help their
social interaction

When they're older.

And the burning question,

In case you ever wanna
tickle a pet rat yourself --

Where's the sweet spot?

Rats are most ticklish
on their bellies,

And on their backs.

Narrator:
They're not quite rodents,

But will our experts share
where they're most ticklish?

I'm not telling you
were I'm ticklish.

I mean, if you tell somebody
where you're ticklish,

That's like giving the plans
to the death star.

You don't do that.

Where am I most ticklish?

Pretty much everywhere.

You just shouldn't
try and tickle me,

I don't like it.
[ laughs ]

♪

Narrator: August 2016.

Oahu, hawaii.

A drone operator spots
some unusual behavior.

Manta rays
are normally solitary.

So the question is,
why are these three together?

And why does their swimming
look synchronized?

Can't help but be mesmerized
watching them swim

In a tighter and tighter circle.

This looks like fighter jets
in formation.

Narrator:
So why have these mantas met up?

And just what are they doing?

♪

♪

Narrator: August 2016.

Oahu, hawaii.

Manta rays usually swim solo,

But these three are together,

And their swimming
looks synchronized.

Why?

Maybe these rays have joined
ranks to talk to one another?

Across the animal kingdom,

A lot of animals have
found very innovative ways

To communicate with other
members of their species.

[ high-pitched barking ]

[ chirping ]

From vocal communication
to reading facial expressions,

Different animals exhibit
different behaviors

To communicate.

For example, peacock spiders.

The males will put on an
elaborate dance to attract

Their female mates.

Narrator: And mobula rays,

A close relative
of the manta ray,

Have an extraordinary
way of communicating.

Mobula rays are known for
jumping out of the water.

And this happens when they
form very large aggregations,

With hundreds of
other individuals.

It's generally accepted
that the jumping behavior

By mobula rays has to
do with communication.

Narrator:
Their belly flop landings

Send sound waves through
the water to others nearby.

Saying, I'm here!

And so it might follow
that the circling behavior

By manta rays also has
to do with communication.

Could these mantas
be having a chat?

Galante:
When you look at this clip,

And they way that the rays
are swimming,

They can all see each other,

And there's no
other rays in sight.

So I don't think they're
trying to communicate.

Narrator: Maybe there are
two males courting a female,

Hoping to win a chance to mate.

This idea of like,
kind of mating chases

Or kiss chases in nature,
is not a strange one.

Lots of animals do it.

Narrator: Could
our three synchronized swimmers

Be in a similar
courtship ritual?

Baker:
The whole ritual of a chase

Is a way of deselecting
your suitors.

So if you are a female
and you're swimming away

From a group of males,
by the end of the swim,

The fittest male
is the one left.

And that's the one
you want to mate with.

Squirrels are very good at it.

You'll see them haring
through the trees

Like a furry tornado,

Shooting around the branches.

And that's basically the female,
leading on males.

Narrator: Mantas spend
most of their lives alone.

When they do meet up,
it's usually for courtship.

Nosal: Mantas have sometimes
been observed

Forming trains of up
to 20 individuals,

Where males are
following females

In order to mate with them.

Narrator: And they'll form lines
to follow her.

Nosal: Whereas, the behavior
we're seeing here,

Are mantas circling
in a tight formation.

And there's no other
mating behavior seen,

So it must be something else.

Galante: Circular swimming has
been seen in one other piece

Of manta behavior,
and that's feeding.

They're filter feeders,

Meaning they gape their
mouths and filter water

Through their gills to pick up
as much zooplankton as possible.

Narrator: Zooplankton
are tiny animals such as krill

That drift along
with water currents.

Nosal: In some locations
where there is just a ton

Of food in the water,
mantas will actually form

Foraging chains, where they'll
follow behind each other.

And this a way of
actually maximizing

The rate of food intake.

It's the most
efficient way to feed.

By swimming in formation,

The mantas create
a feeding vortex,

Which keeps their
food bunched together.

So what looks like
synchronized swimming

Is actually a kind of
social foraging behavior.

The leader gets the
biggest plankton prize.

But they'll switch places,

And each manta gets
a turn up front,

And a share of the meal.

Similar synchronized
circular behavior,

And that's a mouthful,

Has been observed like this
before in the maldives.

What happens is an
upwelling of currents

Push a ton of krill
into a singular area.

And in that area,

Up to 200 mantas will gather,

And they begin to chain feed
in groups of 50 or more,

And they do it in circles.

Nosal: So these three mantas,
instead of swimming in a line,

They're swimming
in a tight circle,

Because they've hit on
a dense area of food.

And what they're doing
is basically cooperating

To get the maximum rate
of food intake.

Narrator: When food brings
these solo swimmers together,

They're surprisingly social

And use synchronized teamwork

To score supper.

♪

San francisco, california.

Tourists flock to this
coastal city each year.

When you think of san francisco,
you think of alcatraz.

And for many people,
they also think of pier 39.

♪

[ sea lions barking ]

Nosal: The sea lions of pier 39

Have become a must-see
tourist attraction.

And they've been like
that for decades.

You could watch these
things for hours,

Playing and fighting
and growling at each other

And pushing each other
off the platforms.

Narrator: But then
something strange happens.

Nosal: All of the sea lions
just disappear

Seemingly overnight
in June 2014.

It was really shocking.

Narrator: No one was more
stunned than sheila chandor,

The harbor master at pier 39.

So all of the sudden
there was sea lions here,

And then there weren't any.

Where were they?
And why had they gone?

Nosal: It's one thing
for a bunch of animals

To disappear slowly overtime.

But for them to all basically
follow each other at once,

It's rather shocking.

And I need to ask myself why.

Why would they do that?

♪

♪

Narrator: June 2014.

San francisco, california.

The city's famous sea lions
all mysteriously disappear

Overnight.

Wildlife biologist,
forrest galante,

Sets out by boat to
get closer to a group

Of california sea lions

To check out what might
make them move en masse.

Galante: We might not have
invented smellovision yet,

But as you pull up to
see a sea lion rookery,

There is a very distinct,
very pungent smell.

And if you ate nothing
but fish your entire life,

I think your poop would
smell pretty bad too.

[ groans ]

[ bell clangs ]

So these sea lions are doing
what's called a haul-out,

Where they'll jump
up on land and rest

To take a break from swimming.

But they're also
in a safe space.

And the reason being,
when they're in the water,

They are susceptible
to predation.

Narrator:
So maybe predators showed up,

And pier 39 stopped
being a safe space

For the san francisco sea lions.

They're has actually been
an incident where a sea lion

Was attacked and killed in front
of some tourists

At alcatraz.

Narrator:
In an incredible ambush attack,

The 3,000 pound shark
explodes out of the water.

[ dramatic music ]

Sharks can jump 10
feet into the air.

And this one caught the sea lion
completely off guard.

♪

But that attack happened
more than a mile away

From pier 39,

In the deep waters off alcatraz.

Great white sharks do
not come into the marina,

Or within the proximity
of the marina,

Because they like deep water,

And they are afraid
of the boats and the activity.

[ sea lions barking ]

Narrator: If the sea lions
weren't evading predators,

Perhaps their seasonal
summer break holds clues,

As there's something surprising

About the san francisco
sea lions --

They're an all boys club.

Most of what you
see here at pier 39,

The majority, are males.

The majority of the females

Stay down in the breeding
grounds in the channel islands.

And every year,
mature male sea lions

Must head off
to hook up with them.

So did the sea lions swim away

To mate with their sweethearts?

Perhaps, as the mating season
seems to match up

With when the sea lions
checked out of pier 39

In June 2014.

The mating season is
normally June and July.

Narrator: Every summer,
these ocean athletes

Swim over 300 miles south
from san francisco

To the channel islands.

Meaning the males leave pier 39

Every summer to pair up.

So the answer to our sea lions
2014 disappearance is mating.

Mystery solved.

[ sea lion barking ]

Well, almost.

What we're used to
is even at the height

Of the breeding season when
the majority have gone south,

There's always a few
of the younger ones left

On the docks because they
can't swim the distance.

This means some sea lions
always stick around.

But something changed this time.

2014, the big difference for us
was they were all gone.

♪

That had never happened,

And actually has
never happened since.

Narrator:
What occurred in June 2014

For all the sea lions to
vanish at the same time?

♪

♪

Narrator: June 2014.

San francisco, california.

The city's famous sea lions
are missing.

There are usually some
sea lions at pier 39,

Even during the mating season.

So why'd they all
vanish at once?

Like most animals,

One of the sea lions'
biggest priorities is food.

Could food be behind
their disappearance?

California sea lions feed on
salmon, krill, anchovy,

Just about any fish that's
out there in the bay.

Narrator: They need to eat

At least 15 pounds of fish
every day.

If they need this much food,

What happens when
lunch runs out?

Certainly, food availability
is gonna drive animal movement.

If there's no food somewhere,

The animals are gonna move
to where there is food.

Narrator: And a strange
weather event in 2014

Could hold clues.

We experienced what's
called an el niño,

When the water
temperature changes.

And it gets warmer.

And what that does is it effects
what's available

For the california sea lion
to eat in the bay.

So el niño caused
a food shortage.

Limited food came at a bad time,

Since it was during
the sea lions' mating season.

Chandor: So, in 2014,

Because clearly there was not
enough food in the bay area,

They had to go further afield

In order to get ready to go
on that long journey down south

To the channel islands to breed.

Narrator: As a result,
the sea lions followed the food.

Remember, they'll eat
15 pounds of fish a day.

But in the run up to mating,

Males can add on an extra
300 pounds of body weight.

Meaning these titans can
weigh in at half a ton.

♪

This extra fat,
called blubber,

Gives them the energy they need
to defend their territories,

Known as rookeries,
in the pinniped world.

The male needs to stay in his
rookery as long as possible

To ensure that he
gets more females.

So the bigger the male,
the more blubber,

The longer he can stay.

If he gets hungry and has
to leave to go find food,

Another male could
take his spot.

So, they have to fast
for up to 27 days

During the mating season.

Narrator: So, males must pile on
the pounds before breeding

To win over the ladies.

This makes food
the key to our story.

A food shortage in the bay,
triggered by el niño,

Coincided with
the mating season.

That's why every single
sea lion vanished in 2014.

Nosal:
Any year you visit pier 39,

Especially during the
months of June and July,

You won't see a ton of
these male sea lions,

Because some of these
have already left

To go and find
their mating grounds.

But in June of 2014,
because of the shortage of food,

Almost all of them had left
to go find food elsewhere.

♪

Narrator:
But as soon as the fish returned
and the breeding season ended,

The sea lions came home.

Much to the relief of
the san franciscans.

And fortunately for us,
as you can see,

They came back.

And we're very happy about that.

[ laughs ]

-- Captions by vitac --
www.Vitac.Com

Captions paid for by
discovery communications