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Narrator: Ever wonder why crows
would gather
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Around the body
of a fallen comrade?
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Man: This must have been
one popular crow.
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00:00:09,276 --> 00:00:12,244
Narrator:
What's electrifying the skies
over venezuela?
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This is the lightning strike
capital of planet earth.
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00:00:15,983 --> 00:00:17,649
Narrator:
And what could cause
a lake shore
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To become smothered
in spider webs?
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00:00:20,755 --> 00:00:23,756
Layers of webs pretty much
covering everything.
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Narrator:
Nature is awe-inspiring,
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But sometimes it just
doesn't make sense.
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Man:
I have never, ever seen
anything like this.
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Strange animal behavior,
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Unexpected events
captured on camera --
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The truth behind them
is astonishing.
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My god!
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Nature's greatest
mysteries, "solved."
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-- Captions by vitac --
www.Vitac.Com
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Captions paid for by
discovery communications
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Narrator:
February 14, 2018,
seattle, washington --
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A seemingly ordinary valentine's
morning erupts into chaos.
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A cacophony of squawks
draws schoolteacher
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Jean sherrard
to the bizarre scene outside.
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Narrator:
A huge flock of crows
has gathered.
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They all seem to be looking
at one individual.
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The question is, "just what is
going on in their bird brains
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To make them do this?"
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This is a really strange
bit of behavior,
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And all sorts of questions
spring to mind
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As to what's actually
going on here.
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Why have they gathered round
this crow?
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Perhaps these crows
gather round to assess it
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And see whether
it's just injured
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Or whether there'd be a way of
that crow coming back around.
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Narrator:
So have these crows gathered to
help out a wounded flock mate?
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After all, the social dynamics
of crow society
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Show these birds of a feather
really do flock together.
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Crows mate for life.
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00:02:06,060 --> 00:02:08,627
And young crows might remain
with their parents
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For 5 or more years,
some of them,
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So that you get really large
extended family groups.
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Narrator:
But there's no room for being a
lazy teenager in a crow family.
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Young crows and corvids
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Will help their parents
to raise siblings.
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Marzluff: And those offspring
will help feed the young,
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Defend the territory,
look out for predators.
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Narrator:
Other animals with strong
social bonds like lions
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Have been known to support
their injured friends.
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Is this happening here?
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Certainly if a mate is injured
in a nonlethal way,
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They will still remain together.
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They do seem to have
a really strong loyalty.
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Crows have been reported to feed
an injured bird
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If it couldn't feed itself.
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There are even reports
of individual crows
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Helping support another bird
who's wounded,
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And I can see that definitely
happening with a mated pair.
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But it's really unlikely
that they would do that
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For unrelated crows.
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Narrator: A group of crows
is called a murder.
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In seattle, this cackling army
is at least 60 strong.
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But crow families have no more
than a dozen members,
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So this gathering is unlikely
to be a family affair.
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So in this instance,
all these crows
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Gathering round to help a crow,
it doesn't seem likely to me.
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Narrator:
There must be something else
going on
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To bring this flock together.
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On closer inspection, it seems
our crow is way beyond help.
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It's dead.
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For a really long time
throughout human history,
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We have noticed that crows
seem to respond
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Really strongly to their dead.
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When a crow dies, a murder
of crows will gather around
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That dead crow in
what's known as a crow funeral.
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A bird will fly in, and it's...
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You know,
as it's going about its day,
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And it will see a dead crow
on the ground.
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One starts to call,
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Others come in,
and they start calling.
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It's a cacophony.
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Narrator: But what's the motive
for this crow funeral?
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Could their interest
in the dead crow
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Be an attempt to come to terms
with losing a flock member?
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Marzluff:
One other reason they could come
in to a funeral
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Setting would be to mourn
the loss of that individual.
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Swift: Maybe it was
an expression of grief.
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One of their neighbors died,
or their mate died,
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And they're coming
to pay their respects.
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Marzluff:
They might actually be having
emotional mourning
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Sort of response to that.
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Narrator:
In the animal kingdom,
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Only a handful of species
like dolphins and elephants
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Respond to their dead
in this remarkably human way.
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Could crows also be a species
that grieves?
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John marzluff is
professor of wildlife science
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At the university of washington
and has been working with crows
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For decades to better
understand their behavior.
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John wants to explore the mental
reactions of wild crows
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When a fellow crow dies.
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After anesthetizing
his subjects,
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He examined
their brains in his lab
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Using a special bird-sized
scanning machine.
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The way we scan a crow's brain
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Is to use
what's called a micro-p.E.T.,
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Or positron emission tomography.
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Narrator:
The p.E.T. Scan will allow john
to see which parts of the crow's
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00:06:06,867 --> 00:06:09,634
Brain light up
during a crow funeral.
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Firstly, to simulate
a crow's reaction to death,
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He showed a crow
a stuffed dead bird.
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John wanted to measure
their mental reactions
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To the dead crow,
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But the result wasn't quite
what he'd expected.
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I kind of expected them to be
very stereotyped,
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In a very simple,
like, response,
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But it wasn't like
they were fearful
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Or even emotional
about this particular scene.
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Instead, what we saw was
that part of their brain
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Was activated that is indicative
of complex decision-making.
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Narrator:
So it seems that the crows
at the funeral are flocking
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Together
not to pay their respects
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But to assess the situation
and make decisions,
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In which case, "what answers
are these brainy birds seeking?"
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Maybe they're turning detective
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00:07:03,724 --> 00:07:05,791
And investigating
the crime scene.
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Perhaps it's a kind of a novel
predator like a unique dog
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Or a human
that they need to learn about.
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Narrator:
To test the theory, john added
a suspect to the crime scene,
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A human holding the dead bird.
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Swift: Well, they have made
this connection
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That this person
holding a dead crow
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Must have had something to do
with their death,
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Or in some way they're bad.
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Narrator:
Adding this new threat element
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Activated a different part
of the crow's brain.
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We saw the hippocampus
activated,
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And the hippocampus is
an important part of the brain
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That is used to form important
social and spatial memories.
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That indicates that these birds
are forming a memory.
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Narrator:
John's results suggested
that wild birds will commit
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These crime scenes to memory,
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But just what exactly
are these super smart birds
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Trying to remember?
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Narrator: February 14, 2018,
seattle, washington --
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A crow funeral
is filmed on a suburban street.
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What are they doing?
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00:08:22,736 --> 00:08:23,935
To find out,
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Scientist john marzluff
has been examining crows
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To see how they react
to their dead,
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And he's discovered that
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They seem to be
trying to memorize the event.
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Crows appear to be really good
at learning from crime scenes,
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And the two things that we know
that they learn,
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And there might be other things,
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Is the location
of the crime scene itself
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And any suspects
that were present
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At the scene of the crime.
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Narrator:
So is our valentine's day
crow funeral in seattle
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Really just one
big crow investigation.
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If so, it could be beneficial
for every bird in the flock.
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00:09:06,947 --> 00:09:09,614
By gathering around the dead
or dying crow,
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What the others are doing
are gleaning information,
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Learning and finding out
what caused the accident,
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What caused their death,
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And once they've got
that information,
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It helps them avoid
a similar end themselves.
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So make sure that they don't
meet the same fate
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As this bird
that has just recently died.
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Marzluff: It pays to be smart
and learn things as you go
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Because you might be able to use
that information in the future.
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Narrator: So it's not so much
a crow funeral.
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It's more like a crow classroom
where the birds learn
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How to keep themselves
safe down the line.
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Oh, and by the way,
no need to worry
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About the welfare of the crows
john used in his tests.
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We wake the bird up, and then
it can be released to the wild
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And go about its own life.
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♪
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Narrator:
October 2018,
lake vistonida, greece --
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00:10:12,613 --> 00:10:14,879
Residents living on the
lakeshores wake up
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00:10:14,881 --> 00:10:17,215
To a very strange sight.
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00:10:21,054 --> 00:10:23,955
Oh, no.
Oh, no. Oh, no.
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00:10:23,957 --> 00:10:26,925
Narrator: Almost overnight,
their beach has been transformed
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00:10:26,927 --> 00:10:29,361
Into an arachnophobe's
nightmare.
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00:10:29,363 --> 00:10:31,229
This is a creepy one.
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00:10:31,231 --> 00:10:33,431
This place in greece
all of a sudden
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00:10:33,433 --> 00:10:36,201
Is totally covered
in spider webs.
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Layers of webs covering plants,
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Pretty much covering everything
and over a huge area.
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00:10:43,510 --> 00:10:45,543
It looks like Halloween
decorations, but it's not.
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00:10:45,545 --> 00:10:47,746
It's totally real.
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00:10:47,748 --> 00:10:51,182
Narrator: The super web spans
almost 1,000 meters.
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00:10:51,184 --> 00:10:53,218
What could be going on
in the spider world
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00:10:53,220 --> 00:10:56,087
To make them spin
such a gigantic structure?
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00:10:58,492 --> 00:10:59,791
Could this be the work
of a group
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00:10:59,793 --> 00:11:03,128
Of unusually social spiders?
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00:11:03,130 --> 00:11:05,830
Spiders certainly aren't known
for their teamwork.
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00:11:05,832 --> 00:11:10,201
Everybody thinks of spiders
as these solo hunters,
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00:11:10,203 --> 00:11:14,406
But there are a few kinds
of spiders that act communally,
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00:11:14,408 --> 00:11:16,207
Almost like an anthill,
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00:11:16,209 --> 00:11:18,977
Where a whole bunch of spiders
will share a great big web,
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00:11:18,979 --> 00:11:22,013
And that could be
what's happening in greece.
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00:11:24,351 --> 00:11:28,319
Narrator:
Of the almost 50,000 species
of spider worldwide,
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00:11:28,321 --> 00:11:32,057
Only 23 species
are truly social.
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00:11:32,059 --> 00:11:34,959
Cooperative spiders
create immense webs,
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00:11:34,961 --> 00:11:37,829
Home to up to
50,000 individuals.
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00:11:40,200 --> 00:11:42,901
So do we have a fast-growing
community
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00:11:42,903 --> 00:11:45,937
Of social spiders
here in greece?
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00:11:45,939 --> 00:11:48,039
They are a species
of orb weaver,
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00:11:48,041 --> 00:11:50,075
Which typically aren't social.
209
00:11:50,077 --> 00:11:52,577
There aren't any
communal spiders in greece
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00:11:52,579 --> 00:11:54,112
Or anywhere near greece.
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00:11:54,114 --> 00:11:57,215
That's not going to
explain this.
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00:11:57,217 --> 00:12:00,051
Narrator:
If there are no social spiders
in greece,
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00:12:00,053 --> 00:12:04,422
Did these long-jawed orb
weavers migrate here?
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00:12:04,424 --> 00:12:07,258
Spiders crawl slowly
through their webs,
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00:12:07,260 --> 00:12:08,893
And they crawl on the ground.
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00:12:08,895 --> 00:12:11,396
Narrator:
But surely they haven't
swum across the lake?
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00:12:11,398 --> 00:12:12,797
What a lot of people
don't realize is
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00:12:12,799 --> 00:12:14,599
That they can also fly.
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00:12:25,512 --> 00:12:29,914
Narrator: October 2018,
lake vistonida, greece --
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00:12:29,916 --> 00:12:32,684
The shoreline looks
like a Halloween party.
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00:12:32,686 --> 00:12:38,490
Spider webs are everywhere,
so how did they get here?
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00:12:38,492 --> 00:12:43,161
Could an army of spiders
have flown in overnight?
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00:12:43,163 --> 00:12:45,196
A spider's version
of an airplane
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00:12:45,198 --> 00:12:47,966
Is just a really
long strand of web
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00:12:47,968 --> 00:12:49,901
That gets caught by the wind,
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00:12:49,903 --> 00:12:52,237
And if the spider is holding
on to its strand
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00:12:52,239 --> 00:12:56,241
And moves with it,
it's called ballooning.
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00:12:56,243 --> 00:12:58,376
They will climb to the top
of whatever
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00:12:58,378 --> 00:13:01,012
Is most prominent
in their environment,
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00:13:01,014 --> 00:13:04,916
So a top of a tree,
blade of grass.
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00:13:04,918 --> 00:13:08,753
They will stand on their
tiptoes, raise their abdomen,
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00:13:08,755 --> 00:13:10,955
Let out silk,
and then float away.
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00:13:10,957 --> 00:13:16,261
♪
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00:13:16,263 --> 00:13:19,197
So they travel huge distances
without any wings,
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00:13:19,199 --> 00:13:22,734
Just using these silk lines.
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00:13:22,736 --> 00:13:25,904
Narrator:
But only some spider species
can balloon,
237
00:13:25,906 --> 00:13:29,107
And it seems unlikely
that so many ballooning spiders
238
00:13:29,109 --> 00:13:33,311
Would happen to land in this
one spot, as once airborne,
239
00:13:33,313 --> 00:13:37,015
They have little control
over where they go.
240
00:13:37,017 --> 00:13:40,218
So could the greek lake
have been their launch site?
241
00:13:40,220 --> 00:13:44,322
Maybe all those long strands
of web have accumulated
242
00:13:44,324 --> 00:13:47,325
And made these big huge webs
that cover everything.
243
00:13:49,396 --> 00:13:51,596
Narrator:
When thousands of spiders
balloon,
244
00:13:51,598 --> 00:13:53,965
The tangle of silk threads
they leave behind
245
00:13:53,967 --> 00:13:58,203
Can be surprisingly
lovely to look at,
246
00:13:58,205 --> 00:14:01,372
But why would a bunch
of long-jawed orb weaver spiders
247
00:14:01,374 --> 00:14:05,210
Be ballooning
in such large numbers?
248
00:14:05,212 --> 00:14:06,911
Well, baby spiders
249
00:14:06,913 --> 00:14:09,848
Have an especially
big motivation to move.
250
00:14:09,850 --> 00:14:13,751
Sixty-five babies can hatch
from just one egg sac.
251
00:14:13,753 --> 00:14:16,087
And these are all
in a very small space,
252
00:14:16,089 --> 00:14:19,991
So there's a lot of competition
and potentially predation
253
00:14:19,993 --> 00:14:22,260
Happening from their brothers
and sisters
254
00:14:22,262 --> 00:14:23,728
As spiders are cannibalistic.
255
00:14:23,730 --> 00:14:25,029
They will eat each other,
256
00:14:25,031 --> 00:14:27,732
So obviously it's a good idea
to disperse
257
00:14:27,734 --> 00:14:30,602
And get far away
from any brothers and sisters
258
00:14:30,604 --> 00:14:33,037
That might want to eat them.
259
00:14:33,039 --> 00:14:36,107
Narrator:
No wonder young spiders
will go to extreme lengths
260
00:14:36,109 --> 00:14:39,043
To find a new home,
261
00:14:39,045 --> 00:14:41,045
But was it a bunch
of baby spiders
262
00:14:41,047 --> 00:14:45,350
Ballooning off to pastures new
that carpeted the lakeshore?
263
00:14:45,352 --> 00:14:47,252
If they were ballooning,
you would expect to find
264
00:14:47,254 --> 00:14:49,387
Just individual strands
everywhere,
265
00:14:49,389 --> 00:14:51,890
And these are well-built webs.
266
00:14:51,892 --> 00:14:53,691
Narrator:
If they're not ballooning in,
267
00:14:53,693 --> 00:14:57,428
Could the solution be something
to do with weather?
268
00:14:57,430 --> 00:15:01,132
This shoreline in greece had
warm and humid conditions,
269
00:15:01,134 --> 00:15:04,602
Which is perfect
for an abundance of mosquitoes.
270
00:15:08,308 --> 00:15:12,810
Narrator:
Millions of mozzies cued
a frenzy of feeding and mating.
271
00:15:12,812 --> 00:15:16,648
So the reason there were so many
spiders in greece all at once
272
00:15:16,650 --> 00:15:17,982
Is because all of a sudden,
273
00:15:17,984 --> 00:15:20,017
There was a ton
of food for them.
274
00:15:20,019 --> 00:15:23,621
With that much food available,
the spiders went to town.
275
00:15:23,623 --> 00:15:25,857
Narrator:
This glut of food and ideal
276
00:15:25,859 --> 00:15:28,426
Weather led
to a breeding bonanza,
277
00:15:28,428 --> 00:15:31,362
And an explosion
in the local spider population.
278
00:15:31,364 --> 00:15:33,798
And that's what resulted in this
huge, huge
279
00:15:33,800 --> 00:15:37,235
Extraordinary webbing
that you saw there.
280
00:15:37,237 --> 00:15:41,105
And so it turns into the
new york city of spider webs.
281
00:15:41,107 --> 00:15:43,841
Narrator:
Perfect weather and lots
of spider food
282
00:15:43,843 --> 00:15:48,179
Means lots of spiders,
and that means lots of webs.
283
00:15:48,181 --> 00:15:50,415
Greek spider town mystery...
284
00:15:50,417 --> 00:15:52,417
Solved.
285
00:15:56,589 --> 00:15:58,990
Astronauts at the international
space station
286
00:15:58,992 --> 00:16:02,527
Capture a dramatic storm
over south america.
287
00:16:02,529 --> 00:16:06,030
One lake in venezuela
is particularly electric,
288
00:16:06,032 --> 00:16:08,333
Which begs the question,
"why?"
289
00:16:10,270 --> 00:16:13,137
Lightning is a very common
occurrence around the globe.
290
00:16:13,139 --> 00:16:16,841
There are around 100 lightning
strikes per second.
291
00:16:16,843 --> 00:16:20,178
That averages out to around
3 billion
292
00:16:20,180 --> 00:16:22,847
Lightning strikes per year.
293
00:16:22,849 --> 00:16:26,951
Narrator:
3 billion strikes --
that's a lot of electricity,
294
00:16:26,953 --> 00:16:30,221
And some places are much
more hit-prone than others.
295
00:16:30,223 --> 00:16:31,556
Riskin: People love to say
that lightning
296
00:16:31,558 --> 00:16:33,524
Never strikes twice
in the same place,
297
00:16:33,526 --> 00:16:35,126
But they obviously
haven't visited
298
00:16:35,128 --> 00:16:37,095
Lake maracaibo in venezuela.
299
00:16:37,097 --> 00:16:39,163
This place is out of control.
300
00:16:39,165 --> 00:16:44,769
[ thunder rumbling ]
301
00:16:44,771 --> 00:16:47,171
Narrator: With an average of 28
strikes a minute
302
00:16:47,173 --> 00:16:49,540
On 300 nights every year,
303
00:16:49,542 --> 00:16:53,711
This place holds the world
record for lightning activity.
304
00:16:53,713 --> 00:16:59,183
This is the lightning strike
capital of planet earth.
305
00:16:59,185 --> 00:17:05,590
Narrator:
The question is, "what makes
this place so electrifying?"
306
00:17:16,603 --> 00:17:19,637
Narrator:
What is causing lake maracaibo
in venezuela
307
00:17:19,639 --> 00:17:22,106
To be the lightning capital
of planet earth?
308
00:17:22,108 --> 00:17:26,177
One possibility is that humans
have done something there
309
00:17:26,179 --> 00:17:29,580
That has caused all
this lightning to show up.
310
00:17:29,582 --> 00:17:32,617
It sounds impossible,
but people can totally influence
311
00:17:32,619 --> 00:17:35,119
Where lightning strikes.
312
00:17:35,121 --> 00:17:37,688
Lightning is always trying
to find the quickest path
313
00:17:37,690 --> 00:17:41,359
To the ground,
the shortest route possible.
314
00:17:41,361 --> 00:17:44,429
Narrator: And in big cities,
that shortest route
315
00:17:44,431 --> 00:17:47,465
Usually starts
with the highest skyscraper.
316
00:17:51,071 --> 00:17:53,704
Are man-made structures
attracting lightning
317
00:17:53,706 --> 00:17:55,039
To this lake?
318
00:17:55,041 --> 00:17:57,442
It's very unlikely
that there would be
319
00:17:57,444 --> 00:17:59,610
Any kind of human element
involved
320
00:17:59,612 --> 00:18:01,579
In terms of a building,
of a city.
321
00:18:01,581 --> 00:18:04,315
Riskin:
You don't have skyscrapers
all around this lake.
322
00:18:04,317 --> 00:18:06,350
It's just a few small buildings.
323
00:18:06,352 --> 00:18:08,853
They're not
empire state buildings,
324
00:18:08,855 --> 00:18:12,290
So they're probably not big
enough to focus the lightning,
325
00:18:12,292 --> 00:18:14,325
And the lightning
is not happening there.
326
00:18:14,327 --> 00:18:16,060
It's happening out
over the lake.
327
00:18:19,999 --> 00:18:23,501
Narrator: This might be the most
electrifying place on earth,
328
00:18:23,503 --> 00:18:25,837
But it's teeming with life.
329
00:18:25,839 --> 00:18:29,207
Jaguars roam the lush banks,
and the lake,
330
00:18:29,209 --> 00:18:32,009
Which is three times
the size of rhode island,
331
00:18:32,011 --> 00:18:37,248
Is home to freshwater dolphins
and over 100 species of fish.
332
00:18:37,250 --> 00:18:43,121
♪
333
00:18:43,123 --> 00:18:46,524
So what could be causing
this region's
334
00:18:46,526 --> 00:18:48,759
Tremendous thunderstorms?
335
00:18:50,730 --> 00:18:53,364
Perhaps something
more industrial.
336
00:18:53,366 --> 00:18:54,799
Midcap:
One of the original theories
337
00:18:54,801 --> 00:18:59,103
Was that it could possibly be
driven by or fed by methane.
338
00:19:01,241 --> 00:19:03,541
So the lightning storm
is happening way off the ground,
339
00:19:03,543 --> 00:19:06,377
Like 50,000 feet up,
and the methane,
340
00:19:06,379 --> 00:19:07,678
If it's coming
out of the ground,
341
00:19:07,680 --> 00:19:09,714
Would have to travel
a long distance to get there.
342
00:19:09,716 --> 00:19:12,283
Now, anybody who has ever
farted knows
343
00:19:12,285 --> 00:19:15,620
That it's going to dissipate
pretty quickly,
344
00:19:15,622 --> 00:19:18,523
And to be honest, it would
look like a giant fireball,
345
00:19:18,525 --> 00:19:21,192
Not a whole bunch
of lightning strikes.
346
00:19:21,194 --> 00:19:23,528
Lightning really doesn't depend
on methane
347
00:19:23,530 --> 00:19:29,033
In any way to feed itself
or intensify strikes,
348
00:19:29,035 --> 00:19:33,004
So methane
has been ruled out.
349
00:19:33,006 --> 00:19:37,241
Narrator:
It's not buildings, and it's not
gas from the oil industry.
350
00:19:37,243 --> 00:19:40,511
Looks like humanity's
off the hook.
351
00:19:40,513 --> 00:19:42,513
Could something natural
be responsible
352
00:19:42,515 --> 00:19:45,349
For lighting up the skies
above venezuela?
353
00:19:45,351 --> 00:19:51,122
♪
354
00:19:51,124 --> 00:19:53,457
So this is a very fascinating
event in that
355
00:19:53,459 --> 00:19:55,259
There are a number
of things going on here.
356
00:19:55,261 --> 00:19:58,429
First and foremost would be
the geography of the region,
357
00:19:58,431 --> 00:20:02,233
So lake maracaibo is
surrounded on three sides.
358
00:20:02,235 --> 00:20:04,468
It's hemmed in to the east,
to the west,
359
00:20:04,470 --> 00:20:07,104
And to the south
by very high mountains.
360
00:20:07,106 --> 00:20:10,775
To the north, lake maracaibo
opens up to the caribbean sea.
361
00:20:10,777 --> 00:20:13,511
So you get all this warm air
that comes from the caribbean.
362
00:20:13,513 --> 00:20:15,012
Midcap: It's warm air.
363
00:20:15,014 --> 00:20:18,916
It's moist air, and it creeps
into the lake maracaibo region.
364
00:20:18,918 --> 00:20:20,284
That air has to go someplace,
365
00:20:20,286 --> 00:20:22,820
But when it enters
the lake itself, it realizes,
366
00:20:22,822 --> 00:20:24,622
"okay, there are mountains here.
There are mountains there.
367
00:20:24,624 --> 00:20:26,357
There are mountains.
Where am I going to go?
368
00:20:26,359 --> 00:20:29,694
I can't go to the side.
I have to go up."
369
00:20:29,696 --> 00:20:31,629
And then you get this cold air
down from the andes,
370
00:20:31,631 --> 00:20:34,198
And it mixes
and causes a thunderstorm,
371
00:20:34,200 --> 00:20:36,033
But the thunderstorm
can't leave.
372
00:20:36,035 --> 00:20:38,269
It's stuck there
and just gets amplified.
373
00:20:38,271 --> 00:20:42,173
And this happens night after
night after night after night.
374
00:20:42,175 --> 00:20:45,776
Narrator:
So the towering mountains are
trapping powerful storms,
375
00:20:45,778 --> 00:20:50,381
And with nowhere for them to go,
every evening is explosive.
376
00:20:50,383 --> 00:20:57,054
♪