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Hello. This is 6 Minute English
from BBC Learning English. I'm Neil.
And I'm Becca.
Neil, what do
the following animals have in common?
Zebras, giant pandas and magpies.
That's pretty easy, Becca.
They're all black and white.
Right! But do you know why these animals
evolved to be black and white?
Hmm. I'm not so sure.
Probably something about survival.
That's usually the answer, isn't it?
It is.
The animal world is full of colour –
shiny blue peacocks
and bright green frogs.
But in fact, hundreds of
animal species are black and white.
In this episode,
we'll try to find out why,
while also learning
some useful new words and phrases.
And remember, all the vocabulary
from this episode
is available on our website
bbclearningenglish.com.
OK. Time for a question
for you, Becca.
According to one theory,
some animals are black and white
to warn potential predators that
they're dangerous or they taste bad.
But what is
the scientific term for this?
Is it: a) camouflage, b) mimicry,
or c) aposematism?
Well, Neil, I'm going to go with c)
just because I've never heard
of that word before.
OK. I like...
I like your style!
Some scientists think
zebras' distinctive black-
and-white stripes prevent bites
from flies and other insects.
Zoologist Dr Martin How
tested this theory
by covering horses, a close relative
of the zebra, in stripes.
Here, Martin discusses his experiment
with Caroline Steel
from BBC World Service programme
CrowdScience:
Do we know what it is about
the stripes that's putting them off?
Is it somehow, like,
visually confusing?
We originally set out
to test whether maybe
there were these
optical illusions at play,
so we did a whole bunch of tests where
we tried different patterns of rugs,
but it turned out that practically
every high-contrast pattern,
every black-and-white
pattern we used,
almost every pattern was
really effective at stopping flies.
Martin conducted a whole bunch of –
meaning a lot of – tests using
different colours and patterns.
Black-and-white stripes created
an optical illusion, a visual trick
that makes your eyes see things
differently from how they really are.
As a result, the flies were put off.
They lost interest and didn't bite.
So zebras' stripes confuse insects,
telling them to look elsewhere for food.
But are there other
reasons animals are black and white?
Nobody who's seen giant pandas in
a zoo would find them hard to spot.
Against a grassy background,
they stand out easily.
But seen from a distance in the snowy
mountain forests where they live,
black and white
makes the perfect disguise.
Here's Professor Tim Caro, a
world authority on animal behaviour,
explaining more to Caroline Steel
for BBC World Service's CrowdScience:
The giveaway for me was 15 photos
of giant pandas,
taken either fairly close up or at a
distance, and in two of those photos,
I was unable to see anything in the
picture other than rocks and snow.
And then later on, I realised that,
in fact, there was a giant panda
in the centre of that picture
some distance away.
Immediately that...
that clicked in my mind.
The pandas were so well camouflaged
Tim couldn't spot them in the photos.
That's when something clicked
in his mind – a phrase used
when you suddenly understand something
after trying for a long time.
Tim understood
that pandas use colour to hide.
He calls this a giveaway –
something that makes it easy
for people to discover
something secret or unknown.
So, are animals black and
white to repel insects, like zebras,
or for camouflage, like pandas?
Let's give the final word
to Hannah Rowland, a researcher
into another black-and-white
animal – penguins.
Really, science never has
a black-and-white answer –
excuse the pun – about the...
with penguins being black and white.
It's often
a very complex mixture of reasons.
The answer to why animals are black
and white is not black and white –
a situation described
as black and white means one
where it's easy to understand
what's right and wrong.
In fact, there's no one reason
why animals are black and white.
Zebras avoid bites, pandas hide
from predators and some animals,
like skunks,
warn other animals they're dangerous.
It all depends
on the specific animal.
And talking of skunks reminds me
of my question, Becca.
According to one theory,
some animals are black
and white to warn potential predators
they're dangerous or taste bad.
But what is the scientific term?
And I chose c) aposematism
because I'd never heard of it before.
Well, that's a great way of choosing.
And it's done well for you
because you're correct.
Woohoo!
OK. Let's recap the vocabulary
we've learned,
starting with 'optical illusion' –
a visual trick
where your eyes perceive things
differently from how they really are.
'A whole bunch of something'
means 'a lot of something'.
If something puts you off, it causes
you to dislike it or lose interest.
A giveaway is something
that makes it easy
for people to discover
something secret or unknown.
The phrase
'something clicked in my mind' is used
when you suddenly understand
something at last.
And finally, if you describe
something as black and white,
you mean it's easy to understand
what is right and wrong.
Once again, our six minutes are up,
but head over to our website,
bbclearningenglish.com,
for a quiz and worksheet
for this episode.
See you there soon.
But for now, it's goodbye.
Goodbye!
Vocabulary
Word 1 of 15evolve
word
0:25
"to develop gradually over many generations."
More Listening Practice
About this lesson
Explore the science behind why some animals have black and white colouring and what purpose it serves in this 6 Minute English episode.