Narrator: What if...
Woman: That is enormous.
...Elusive deep-sea fish could help us predict earthquakes?
[ screaming, gasping ]
What exactly are they detecting?
Narrator: And what is the point of this pointy egg?
Okay, that's a big question.
Narrator: Nature is awe-inspiring,
But sometimes it just doesn't make sense.
Man: I have never, ever seen anything like this.
Our team of experts investigate the weirdest animal behavior.
That's amazing.
And the most unexpected events...
What is causing that?
...Ever caight on camera.
Woman: My god.
These are nature's strangest mysteries...
"solved."
-- Captions by vitac -- www.Vitac.Com
Captions paid for by discovery communications
Narrator: Planet earth -- 300 million years b.C.
The dinosaurs are already using an incredible delivery system
For bringing their young into the world.
Perfect for incubation,
Eggs are strong on the outside and safe within.
And now 300 million and some 2,000 years later,
The dinosaurs' descendants, birds, are still laying them.
But there is one question
Scientists haven't quite unscrambled --
Why are birds' eggs such different shapes?
The shape of eggs has excited speculation
For hundreds of years.
♪
We tend to think of eggs as being egg shaped,
But the variation that we get across different species
Is remarkable.
[ birds chirping ]
Hummingbirds have these little tiny bullet-shaped eggs.
Birkhead: Others like waders produce rather pointed eggs.
Of course, the most extreme end, you have the kiwi,
Which gives birth to a very large oval egg.
The human equivalent of giving birth to a 4-year-old.
Narrator: There are around 18,000 species of bird,
And amazingly, almost as many varieties of egg.
And that really throws up a question of, "why?"
It's a mystery.
Narrator: Some eggs are round, some are long,
And others are in between,
But why is each kind of egg a different shape,
And what exactly determines the shape of an egg?
It was a puzzle no one could solve until 2017,
When scientists thought they'd finally cracked it.
Researchers found a correlation between the shape of an egg
And the flight performance of a bird.
Narrator: The scientists examined photos
Of nearly 50,000 eggs,
And compared them with the birds' lifestyles.
Birkhead: The main conclusions were,
Birds that spent a lot of time in the air
Tended to produce rather elongated eggs,
And birds that didn't spend a lot of time in the air
Produced rather squatted, dumpy eggs.
When I first heard this,
It sounded a little bit bizarre to me,
A little bit like the ancient study of phrenology,
When the shape of one's head
Indicated your likelihood of criminal behavior.
It was all a bit weird.
Narrator: It might sound weird,
But there was method to the madness.
If a bird is going to fly well, it needs to be,
Well, aerodynamic.
And that means having a thin and streamlined body.
So any eggs growing inside them must expand lengthways
So the eggs end up narrower, or pointy at one end.
Got it?
Good flyers, thinner birds, thinner eggs.
Easy.
But did the theory stand up?
♪
Greive: So swifts, as the name implies,
Are very gifted flyers.
Their eggs are incredibly elongated,
Consistent with the researchers' theory.
On the other hand, you have birds like owls
Who only fly very short distances occasionally,
And their eggs are almost perfectly spherical --
Again, consistent with the theory.
♪
Narrator: So one of the biggest mysteries
In the avian world had been solved.
Well, maybe, because one egg defied the theory completely.
There's an exception to the rule, as always.
And this is the egg of a bird called the guillemot.
♪
Narrator: Known as guillemots, or mirrors,
In the breeding season,
These sea birds congregate on cliffs
In groups of as many as 5,000
Because they need to be stimulated by a noisy crowd
If they're to mate successfully.
The guillemot belongs to a family of birds, the auk family.
Actually, I'm getting off on a tangent now.
I'll come back again. [ laughs ]
It has a very elongated egg.
One end is very pointy,
And the other end is very rounded.
Narrator: Scientists found that the pointiest eggs --
Call them asymmetric if you want to be fancy --
Tended to come from the top flyers,
But the guillemot was going against the grain.
Greive: The egg itself is asymmetric,
Indicating that the guillemot
Must be an exceptionally gifted flyer,
But in fact, they're absolutely rubbish.
[ chirping ]
They spend almost their entire lives bobbing about
Like a feathered cork on the ocean
And seldom fly at all.
And when they do, they don't do it very well.
[ birds chirping ]
Birkhead: Guillemots are pretty awful flyers.
You know, they flap like crazy just to stay up.
Narrator: They're no soaring eagle.
♪
In fact, the sea bird's wings are more adapted for diving.
They reach depths of 600 feet,
Where those stubby wings make perfect flippers.
It's a great way to catch fish.
And they only need to move off the sea
And up the cliffs when it's time to raise their young.
But the chicks don't hang around for long.
Burke: The chicks will stay on that cliff ledge for a few weeks,
But as soon as they're strong enough and big enough,
They take this incredible leap off the cliff.
♪
Narrator: These chicks are even worse flyers than their parents.
At just three weeks old,
They hurl themselves off the cliff and hope for the best.
♪
They go into a phase where we call them jumplings,
And as a paratrooper, I especially appreciate
This suicidal urge to leap from the cliff
Into the void, where they land
Hopefully in the sea, and not the rocks.
Narrator: Some jumplings
Need a little parental encouragement.
♪
[ squawking ]
So it seems safe to say guillemot's pointy,
Or asymmetric, eggs
Aren't related to their strong flying technique.
With that in mind, why on earth would the guillemot
Have such an exceptionally asymmetric egg?
Pfft. [ laughs ]
Okay, that's a big question.
Burke: One explanation is
That the shape of the egg prevents them
From rolling off the cliff edge.
They balance their eggs in a small space,
And obviously an egg rolling off is a very real risk.
Narrator: Guillemot parents take turns to incubate their eggs,
And changeover is a risky time.
They're just one clumsy move and one cracked egg away from
"worst parent of the year" award.
[ squawking ] emperor penguins also have
A precarious nesting arrangement.
They have pointy eggs, too, and for a very good reason.
Greive: The eggs are perfect for being balanced on the feet
To be kept above the frozen ice and snow.
Narrator: So with that in mind, could guillemots lay pointy eggs
To stop them rolling off the cliff edge?
Tim has been studying these birds for 46 years
And wanted to find out.
If you take a guillemot egg and roll it on a smooth surface,
It will indeed roll in an arc.
But that arc is quite big
Relative to the width of the bank
On which these birds breed.
Narrator: Which means the egg would roll right off the edge.
So that pointy shape should be a disadvantage.
Clearly, stopping them from rolling off the cliffs
Is not the answer.
So, they're not stopping them rolling off cliffs.
They're not helping them fly.
Why are their eggs pointy?
[ insects chirping ]
Narrator: For centuries, scientists have wondered
Why the guillemot egg is such a pointy shape.
Most birds that lay pointy eggs are excellent flyers,
But not guillemots, so how come?
♪
Greive: Is the shape inherently stronger?
One of the things that guillemot eggs face
Is the risk of being broken by a clumsy guillemot
Coming in and crash landing on an incubating bird,
So I wondered whether this particular shape
Would minimize the risk of the egg being broken
If another bird landed on top of it.
Narrator: But it turns out, this pointy egg
Isn't actually the strongest shape.
A perfect sphere, a perfect round object
Is the strongest structure in nature.
It's why we've designed deep-sea submersibles the way they are.
It evenly distributes the pressure
Across the entire surface.
The largest egg we know of, the ostrich egg,
Is almost perfectly round and is strong enough
To support the weight of a human being standing on it.
But in the case of the guillemot,
The eggs are the opposite of spherical.
Therefore, we have to imagine
There's some other virtue to this unique design.
♪
Narrator: Sometimes, solving a science problem
Must feel like scaling a cliff.
But then, after hundreds of hours on the rocks,
Tim finally had a breakthrough.
Doing field work, I had the opportunity
To simply place the guillemot egg on a sloping bit of ledge.
I was staggered to see that a guillemot egg just stayed put.
Narrator: Tim had discovered
That only the most asymmetrical eggs
Could stick to the most extreme cliff faces.
Birkhead: We tested this very rigorously,
And it's true -- the more pointed the egg shape,
The steeper the slope that it can sit on.
It made me realize that stability was the explanation
For why the guillemot egg is this shape.
Narrator: So the reason the guillemot egg
Breaks all the rules --
It helps them cling to their precarious nests.
It's a perfect example of natural selection in action.
Less pointed eggs rolled off the cliff,
So the birds that laid them lost all their chicks.
Birds that laid pointy eggs saw their chicks survive,
So their genes are still going strong today.
[ insects chirping ]
♪
Narrator: Mexico -- April 2014.
Kayakers looking for adventure
Get a bit more than they bargain for.
-Uh-oh. -Oh, my gosh.
Woman: My god, look at the size of the thing.
-It's going under your boat. -Oh, my gosh.
And I'm taking a movie of it.
Narrator: And this little movie went viral,
With over 6 million views online.
Oh, boy. Oh, boy.
It was quite a shock for the woman with the camera.
Woman: That is enormous.
♪
Narrator: The kayakers had stumbled across an oarfish,
An animal rarely seen by humans
Despite the fact it lives in all warm oceans.
♪
It is normally hidden away in the deep,
3,000 feet below the surface.
Conley: Normally when we find these guys,
You're gonna find them in a vertical position in the water,
Their head toward the surface of the water
And their tail towards the deep.
And they sort of undulate and sort of swim
In a vertical manner.
Narrator: Oarfish are huge.
In fact, the giant variety is the longest bony fish alive.
Conley: They're so long, they can get up to
56 feet long, 600 pounds.
They're very large fish.
Narrator: Only a few videos exist
Of an oarfish in its natural deep-sea habitat.
More people have seen earth from space
Than witnessed this rare aquatic species in the wild.
Just hear how excited this deep-sea diver is
To finally see one.
Man: There it is. There it is.
♪
This is incredible.
This is absolutely incredible.
♪
Narrator: Yet, in the last few decades,
Dozens of oarfish have washed up on beaches all around the world.
This one was found
By u.S. Navy seals
On a san diego beach,
And measured 23 feet long.
So what are these rarely seen
Denizens of the deep doing in the shallows?
Well, there are some surprising possibilities.
Some of the sightings have coincided
With looming natural disasters.
Nosal: What's interesting is that sometimes a string
Of these oarfish will wash up right before an earthquake hits.
[ gasping, screaming ]
Some people think that they are sensing
These impending large events.
Woman: Baby, the water's coming to an end!
Narrator: In 2010, dozens of oarfish beached themselves
Before earthquakes in both chile and haiti.
At least a dozen more were found on the shores of japan
In the months before the devastating tohoku earthquake
In 2011.
♪
In which case, could our oarfish have swum up to a mexican beach
Because it senses an impending earthquake?
Moser: Earthquake scientists have
Amazing types of instruments
That are doing everything they can
To detect very minute ground shakings.
And you know, we as human beings still can't predict earthquakes,
And so it would be really incredible to think
That these fish seemingly have learned this trick.
Narrator: These recent beachings aren't the first time oarfish
Have caught our imagination.
♪
There are a lot of stories from ancient history of mariners
Finding strange mythical creatures,
And one of those turns out to be the oarfish.
When you go back into ancient japanese folklore,
These oarfish were known to let the people know
That an earthquake might be coming.
Narrator: So could this ancient myth be right?
♪
Do these deep-sea dwellers
Hold seismic-sensing powers?
Nosal: If oarfish were somehow detecting earthquakes,
How would that work mechanistically?
What exactly are they detecting?
[ insects chirping ]
Narrator: In April 2014,
Kayakers stumbled across an oarfish
By a beach in mexico.
Throughout history, these deep-sea fish
Have often washed ashore before earthquakes.
So, could it be detecting an imminent quake?
Moser: There are actually multiple different types of waves
That propagate from an earthquake,
And some of those waves actually propagate through liquid.
Nosal: The oarfish might be able to hear certain sounds
Or to feel certain vibrations
That certainly would be transmitted through the water.
♪
Narrator: If so, they wouldn't be the first animals to be found
To have a seismic sixth sense.
Some animals can detect earthquakes
Right before they're about to happen.
Some birds are known to do this.
Dogs are known to do this.
Narrator: Eureka, california --
January 2010.
This dog has sensed something.
It's out the door.
[ rumbling ]
And sure enough, the earth starts to move.
[ clattering ]
So if an oarfish washes ashore,
Would you be right to run for the hills?
[ rumbling, clattering ]
These animals are probably detecting
The very minute vibrations
Right before the major shaking starts,
So we're talking about predicting earthquakes
On the order of seconds, not hours or days.
Certainly I don't think that oarfish would be able
To predict an earthquake days before one occurs.
Narrator: Even if, like many other animals,
Oarfish can detect earthquakes,
It seems unlikely they could do it far enough in advance
To swim all the way up from the depths to reach the shore.
So why are they swimming in the shallows?
Could there be something in their biology
That might explain it?
Narrator: October 13, 2013.
One oarfish that entered
The shallow waters off catalina island
In southern california
Was found to be a female full of thousands of eggs.
In which case, could she have come here to reproduce?
Most of the oarfish that have washed ashore are females.
When we open them up, we find that they're full of eggs,
But the eggs are at different developmental stages.
So could there be some behavior associated with spawning?
Narrator: Spawning, a.K.A. Fish sex.
♪
Spawning near the shore is actually quite common
For many species of fish.
Every summer, capelin throw themselves out of the water
And onto the beaches of the north atlantic
And north pacific coasts in their millions.
The females lay their eggs in the sand,
Where the males fertilize them before returning to the sea.
It's a capelin beach party.
Might oarfish be doing something similar?
♪
Oarfish have been observed
Spawning off the coast of mexico.
And in fact, our amazing footage of the oarfish
That startled the kayakers was shot in mexico, too.
It's thought the fertilized eggs stay at the surface of the ocean
Until the baby fish hatch
Before eventually swimming down to their deep-sea home.
So it's possible, since these guys
Are sometimes found in pairs,
But the problem is they're very elusive,
We don't really know much about
The reproductive history of this fish.
Narrator: So if they're not coming ashore to spawn,
And they're not detecting impending earthquakes,
Just what is driving these fish out of the deep?
The answer might lie in the motion of the ocean.
[ insects chirping ]
♪
Narrator: Kayakers in mexico got a startling sight,
An oarfish in shallow water,
And there have been other reported cases
Of these deep-sea fish
Washing ashore all around the world.
They're not predicting earthquakes
Or coming up to spawn, so what else could be going on?
The answer may well lie with the very waters they're swimming in.
Warming of the waters often changes the currents,
It changes the direction of the currents,
It changes the swiftness of the current,
So it's very likely that the currents changed
And ended up washing
Some of those oarfish too close to shore,
And they were unable to swim back
Because they are such weak swimmers.
♪
Narrator: It may seem weird for a fish to be a bad swimmer,
But in the ocean depths where oarfish live,
There are hardly any currents.
That means they don't build up much muscle mass,
And so lack the strength to cope in turbulent waters.
♪
And oarfish are not
The only ones to be swept away.
Ocean currents can be so strong that even whales
And turtles can be pushed off course.
So, is this what happened to our oarfish?
Kind of being at the wrong place at the wrong time,
They end up washing ashore.
Narrator: So the solution is as simple as ocean currents
Driving oarfish to shore.
Perhaps this one's hoping the tide will change
And whisk it back to the deep
And away from the curious crowds.
[ insects chirping ]