Prairie Dogs - Talk of the Town Natural World

The North American prairies, home to the bison.

But this film isn't about the bison.

It's about a tiny creature that lives beneath the bison's feet...

..the prairie dog.

You might easily overlook the prairie dog,

until it opens its mouth.

SQUEAKING

It's a little animal with a big voice.

A team of scientists believe this noise

is in fact a very complex language,

which is remarkable for an animal many see as lowly vermin.

So, what are they saying?

To find out, scientists have devised a set of cunning experiments.

But could these barks, squeaks and chirps really be a language?

To our human ears, this just sounds like a lot of unnecessary noise,

but to other prairie dogs it's all part of a jolly good conversation.

That is, if you believe this man,

prairie dog expert Professor Con Slobodchikoff.

Prairie dogs have the most complex natural language

that's been decoded so far.

They have words for different predators, they have

descriptive words for describing the individual features of predators,

so it's a pretty complex language that has a lot of elements.

A relative of the squirrel

with a language second only to humans in its complexity?

That's a bold claim.

But Con has a problem.

He's fighting an in-built prejudice against these little rodents.

Convincing the wider world that prairie dogs are great linguists

is proving a tough challenge.

He believes if we just get to know them a little better,

understand their world, then we might just see his point of view.

Life as a prairie dog is complicated.

It's not just a simple matter

of eating grass and minding your own business.

You have to share your space with lots of other prairie dogs.

Every prairie dog is part of a big community called a town.

The largest prairie dog towns stretch over tens of miles,

their excavated homes pockmarking the prairie landscape.

Living together requires impeccable social skills.

Kissing is all the rage in prairie dog town.

A little taste of saliva

is like a calling card that helps identify a visitor.

Prairie dogs, though, are nervous creatures,

always on the lookout for signs of trouble across town.

But what is there to worry about?

Prairie dogs aren't the only animals living in the town.

Squatters have moved into some of their vacant burrows.

All these strangers make prairie dogs a little nervous.

And so they should be.

Prairie dogs are under attack from all quarters.

There are times when they must feel besieged

by animals that want to eat them.

Even when they retreat to their underground burrows,

the prairie dogs can't really relax.

With no safety anywhere, above or below ground, prairie dogs

have come up with a clever strategy for dealing with these threats.

LOUD SQUEAKING

They shout.

Very loudly.

Technically speaking, it's an alarm call.

You might still be wondering why Con would choose

such a humble subject to study animal language.

After all, there are more likely animal linguists -

whales or monkeys.

But there was something about those prairie dog alarm calls

that piqued his interest.

With so many predators living in prairie dog town, Con wondered,

do the prairie dogs have just one call,

or do they have different calls for the different predators?

There's only one way to find out.

Con must test their calls.

He's on his way to a remote ranch in the north of New Mexico.

It's a haven for prairie dogs.

Two species live here, Gunnison's and black-tails.

Joining him are two of his students, Patricia Dennis,

who will help record the calls,

and Bill Briggs, who's devised a series of experiments

to test the prairie dogs.

Together, this team hopes to show once and for all

that we have underestimated the little prairie dog.

First of all, Con looks for signs of predators in his research area.

Here's a badger excavation.

This is very fresh.

It probably happened in the last day or two.

This is the way that badgers typically hunt.

They'll excavate a prairie dog burrow and then go inside,

and while the prairie dogs are sleeping,

they will eat the prairie dogs

and then they'll also sleep inside the burrow.

They typically excavate a number of burrows

all around us in a particular area, and then they move on

to another place once they've eaten all the prairie dogs

that live in a particular burrow system.

The presence of predators is welcome news for Con.

The prairie dogs should be on a state of alert,

and that'll mean good alarm calls.

SQUEAKING

But waiting for predators to appear would be far too time-consuming.

These imaginative scientists have a solution -

they bring their own.

Time to set up the first experiment.

Bill must keep the dummy predator under wraps

while he finds a suitable spot.

Some prairie dogs are already a little spooked.

Con uses his car as a screen to hide behind.

It's important that no-one is visible.

The predator is revealed...

..a plastic coyote without any legs.

It seems like an encouraging result.

The prairie dogs are certainly being vocal.

What's really wonderful about this is that other individuals are chiming in

just in response to the vocalisation,

so they don't even have to see the stimulus

in order to know that this is a coyote, and they start yelling.

Every call recorded must subsequently be analysed by Con.

We can hear the difference in the calls

between the different predators, but that's not really enough for us.

What we really need is some sort of analytical tools

for measuring what the frequency and time elements in the call are.

And so this software here allows us to do this.

This is our alarm call elicited for a coyote,

and we can hear that it has a series of rhythmic chirps.

We think that each prairie dog

has its own individual, unique tonal qualities,

just like humans have different voices and different voice prints.

But even though each individual prairie dog might differ,

all the prairie dogs have a common call

for a coyote even within those individual voice print differences.

So we think that when a prairie dog is calling for a coyote,

they probably know who the prairie dog is that's calling,

just the same way that we can on the telephone hear somebody's voice

and immediately recognise it as a person that we know.

SQUEAKY CHIRPING

Everything is ready for experiment number two, the stuffed badger.

Con and his team are very excited by this one.

This is the first time they've ever tested a badger.

Will the prairie dogs have a specific alarm call for it?

The badger's out.

LOUD SQUEAKING

Well, the prairie dogs are certainly calling,

but are these calls different from the earlier ones to the coyote?

Con hopes so.

Now the researchers must take a look at all the recordings

from today's experiments.

The badger call is an entirely new call for us.

We've never recorded a call for a badger.

So it's really exciting to look at the structure of this call

and see what it looks like.

And it looks very different

from any of the other calls that we've recorded.

SQUEAKING

SQUEAKING

HIGHER-PITCHED SQUEAKING

To Con's expert ears and eyes, there is a difference both in their calls

and in the shape of their sound graphs.

The shape of each sound curve

varies subtly, but is consistent for each predator.

But to convince any would-be doubters,

Con has another experiment planned.

Over his 30 years of research, he's noticed that prairie dogs

react in different ways to different predators.

If the alarm calls for coyote and badger do indeed differ,

then playing back the two calls

to a group of prairie dogs should produce distinct responses.

Bill's big speakers get fired up.

HIGH-PITCHED SQUEAKING

First, the alarm call for coyote.

The prairie dogs react instantly.

Having spooked one part of the colony with the loudest

alarm call they've ever heard,

the team moves on to an undisturbed spot

to try out their second alarm call, the badger.

SQUEAKING

The reaction is very different.

We had a terrific response, and for the coyote call

they did just what they're supposed to do for a coyote.

They ran to the burrows and stood at the lip of the burrows and watched.

For the badger call, they ran to the lip of the burrows

and crouched down, just like they're supposed to for a badger.

So it was a terrific result.

Adopting different tactics for different predators

makes perfect sense.

A coyote will hunt by surprise,

so perhaps it's safest to sit up and keep an eye on it at all times.

Badgers are the bulldozers of the predator world.

They will dig into a prairie dog hole.

Crouching down might be a way of hiding yourself

so the badger doesn't choose your burrow.

It's been a good day for the team.

Every new alarm call is a new addition

to their dictionary of prairie dog words.

But there's still a long way to go

in their quest to prove that prairie dogs have a complex language.

It's early morning, and the prairie dogs are already up.

Con and his team are back, and they're keen to try a new test,

one that's a lot stranger than their earlier experiments.

Con has a hunch that prairie dogs have unique calls for colours.

It sounds a bit mad, but he's putting it to the test.

(Patricia here's doing a coloured shirt experiment.

(The idea here is to test the ability of the prairie dogs

(to discriminate between different colours

(and how they incorporate that information into their alarm calls.)

No joy. The prairie dogs aren't calling.

(I think one problem is that Patricia's not threatening enough.

(She tends to walk slowly and is kind of relaxed about it.

(I wonder if we could get Bill to wear a shirt.)

Time to substitute Bill for Patricia.

Bill's manly walk provokes a response.

SQUEAKING

But behind this quirky experiment is a bigger question.

Could the prairie dog calls actually contain more information

than just the identity of the threat?

Could they be describing precisely what they see?

Con believes the answer is yes.

Throughout his 30-year study, he's found that changing the speed,

direction and even the colour of a threat

results in a change in the prairie dogs' alarm call.

We think that each one of these chirps contains a noun-like word

and it also contains adjective-like words,

which describe the colour, the size, and all of that is

put together into one of these single chirps,

pretty much the same way that we would put together a sentence.

So, we might say, "A tall, skinny coyote with yellow fur,"

and the prairie dogs manage to put all of this into a single chirp.

In other words, prairie dogs can cram into one short call

the same amount of information found in a human sentence.

How do they do it?

Con suspects the answer lies in the fine detail of their calls.

Each alarm call or each chirp is a series of stacked harmonics,

that you can see one on top of the other,

but instead of being actual multiples of the base frequency,

they're actually modulated by the vocal apparatus of the prairie dog,

and that's what contains the information that this is a coyote

as well as the general colour and size and shape of the coyote.

So prairie dogs can subtly alter the meaning of their chirp

by varying each harmonic.

It's an amazing way of tightly packaging information.

All these findings demonstrate

this is an animal we have grossly underestimated,

that the prairie dog is much more complex than we thought.

This is no surprise to the man

who has doggedly championed prairie dogs his entire career.

Everything about prairie dogs points to them being complex animals -

even their homes.

This is a prairie dog hole.

It is part of an elaborate burrow system that is underground.

The hole goes down maybe about between one and three metres,

and then the entire burrow system

stretches out for anywhere between three and five metres,

with a fairly elaborate structure.

There's a bathroom chamber where they pee and poop

and there's a nest chamber where they sleep.

There's also side chambers, where one prairie dog coming down

meets another prairie dog coming up,

and one of them backs into a side chamber

so that the other one can go past,

just like two cars on a narrow, winding mountain road.

The prairie dog burrow system

is remarkably sophisticated in its engineering.

These rodents can excavate an extensive

tunnel network that connects as many as six entrance holes.

And it's deep underground where the pups are born in spring.

Blind and without fur, they huddle together for warmth and security.

This underground world of prairie dogs is rarely observed.

It will be five weeks

before the pups are ready to leave their nursery chamber.

When that moment arrives, Con will be there.

The pup calls will be crucial to his work.

Above ground, the mounds are designed

to funnel rain away from the holes and so keep their burrows dry.

The hard work by these mining rodents

has created a vast infrastructure

that makes the prairies attractive for other animals.

Many different species of all shapes and sizes

have come to rely on prairie dogs for their lodging.

Only recently have we come to recognise that without prairie dogs,

the prairies would be lost for ever.

They're important to all life on the prairies,

including lots of animals that want to eat them.

Con believes this relationship with other animals is the main reason

why prairie dogs have developed a complex language.

So what happens to the language if you take away all the predators?

There's only one place where he can find the answer to that...

..at a zoo.

These prairie dogs have been in captivity all their lives.

They've never seen predators.

So what will happen when Bill and Patricia introduce

their dummy predators?

Will these captive prairie dogs

have a call for threats they've never seen before?

The coyote makes its entrance.

SQUEAKING

Well, they're certainly calling.

But are they saying, "Coyote"?

Right now, we've got about eight mics in here to make sure that we've got

no problems with echoes or any other aberrations,

and we're recording the prairie dogs' call to a coyote.

And I'm watching here on the computer screen to look at the spectrograph

to see how it's formed. And to tell you the truth,

it's completely different than what we're used to.

We still have individual chirps, but they have no definition to them.

They're completely different, and it's really surprising to see.

They're making a noise,

but it doesn't sound like a prairie dog word.

Now it's the badger's turn.

Is he doing anything or just looking at it?

There's two prairie dogs right now calling.

There's one calling at the badger

and another prairie dog by the metal grate.

I've got a badger sitting out there,

and we've got two prairie dogs calling for it.

And the spectrograph is just amazing.

It's nothing like we've seen before.

We've got the chevrons, but there's no structure to them.

Their calls are like a scream.

It's an alarm, but without any meaning.

It suggests they only develop their words

after repeated exposure to predators.

If so, that's learning,

and that's a key characteristic of a proper language.

Bill and Patricia's results from the zoo

show that animals who have been in a zoo setting for at least nine years,

who have not heard any predator calls,

probably lose their predator calls or lose the ability to make those calls.

The zoo animals have very non-specific noise-like calls,

and so I think that this shows that learning is important

in this animal language.

This is a major discovery.

Learning is a crucial element of every language.

But can Con build on the zoo results

and demonstrate learning is taking place out on the prairies?

If prairie dogs are learning their calls,

then it must be happening once the pups come above ground.

This, after all, is the first time they'll see other animals.

Testing their ability to learn will be the most important experiment

of all to prove that prairie dogs have a complex language.

Con's reputation and the reputation of all prairie dogs

now depends on the pups.

In early June,

the pups are just taking their very first steps above ground.

Bill is setting up an experiment with a new fake predator.

This is a silhouette of an airborne predator, like a hawk.

And we'll shoot this down this line to try and simulate a hawk attacking

a prairie dog in the colony, and it should be pretty exciting to see.

Well, this is pretty disappointing.

We've done this experiment before in the past,

and the animals at other sites

have given a characteristic hawk call and then they run to their burrows.

But here, they just simply run to their burrows

and they don't give a call.

Maybe they don't see any aerial predators

and so have no reason to give a hawk call.

But nevertheless, it's really disappointing.

Perhaps prairie dog pups are a lot cannier

than we give them credit for.

Maybe Bill's fake hawk wasn't quite realistic enough for them.

This is more like it.

A swooping hawk

is enough to create a state of panic in prairie dog town.

Many prairie dogs will go underground.

If the aerial approach isn't successful,

then the hawk has another strategy -

just sit and wait.

And wait.

The one thing you don't want to do is go above ground,

not when there's a big hawk outside.

But pups can be a little impatient.

A hawk can hold prairie dogs hostage like this for many hours.

Both the prairie dogs and the hawk want to feed.

It becomes a battle of wills.

Eventually, the pups claim victory.

Back at his study colony,

Con is worried that there aren't as many predators as he thought,

and that's making it difficult to record pup calls.

He needs to get the colony on a higher state of alert,

so he has a plan to stir things up a bit.

-Hi, Brent.

-Hey, Con. How you doing?

-It's good to see you.

-Good to see you.

-So, these are your dogs?

-Yeah, these are my two dogs.

And when they're not chewing on each other,

they like to go after varmints like prairie dogs!

The purpose of this is to get the prairie dogs

more used to having predators around.

This colony probably has not had very much predation,

and they aren't calling as much as I would like.

And so having the dogs running around gets them more alert

and gets them to call more for other stimuli,

like some of the other experiments that we're going to do.

This isn't the first time Con has introduced prairie dog to real dog.

What we've found in the past is that they do recognise individual dogs.

They can describe the shape of the dogs,

the size of the dogs and the coat colour of the dogs.

But have the dogs had the desired effect?

Have they stirred up this colony?

Only one way to find out.

The pups seem to be on high alert, but will they call?

Everything is in place.

Now it's all down to the pups.

The tension is becoming unbearable.

SQUEAKING

The plastic coyote has worked its magic again.

But are the pups actually saying, "Coyote"?

If, as Con suspects, the pups learn the alarm calls,

then at this early stage of their lives,

he wouldn't expect them to know the calls for different predators.

Every call recorded

will be subjected to stringent scientific analysis.

Look at the difference.

But at first glance, the findings look positive for Con.

Now, he does have the same number of calls per series,

it seems like, and the loudness and everything else is the same.

And maybe the loudness and the number of calls is something that is innate,

and maybe the structure is something...

Side by side, the adult and pup calls are very different.

SQUEAKING

We have here a pup

and an adult calling for the coyote.

They sound very different,

and they also look very different on the computer.

We can see here the adult call has a lot of structure in it

and it contains a lot of information.

The pup call, on the other hand, doesn't have very much information

in it and it changes in structure, just like babbling in little kids.

So this pup is gradually acquiring more and more structure.

As in any language,

the youngsters must practise getting the words right.

In human babies we call it babbling,

and it appears that prairie dog babies babble, too,

as they struggle to make the right call.

These results are good news for Con,

but they don't prove they're learning, not yet.

To really show that, they'll need to test the same pups later in the year

to see if their calls change over time.

For now, there's nothing the team can do

but wait for the pups to grow up.

That is, if they're able to grow up.

Prairie dog pups are an ideal snack for hungry predators.

You might think the alarm calls of prairie dogs would make

it particularly challenging for a predator to hunt them.

But that doesn't seem to worry this family of swift foxes.

They've made a home in a deserted prairie dog burrow

right in the middle of a colony.

The fox cubs aren't even attempting to keep a low profile.

It's almost as if they're deliberately taunting

their prairie dog neighbours.

With four energetic cubs, Mum has a busy time.

She must hunt regularly.

When she goes out hunting,

the prairie dogs soon sit up and take notice.

But they're remarkably quiet.

Alarm calls warn of a pending threat,

but if that threat comes too close, prairie dogs will often fall silent.

To call out now could prove fatal.

If a pup does indeed learn from its parents,

then knowing when to hold fire and retreat

could be one of the most valuable lessons of its life...

SQUEAKING

..or the end of its life, if it gets it wrong.

When one of your neighbours is killed,

it wouldn't seem unreasonable to expect a moment of quiet reflection.

But once the swift fox is out of sight,

something quite extraordinary happens in prairie dog town.

LOUD BARKING

It looks like the prairie dogs are experiencing a moment of madness.

This acrobatic display is in fact the jump-yip call.

It could be an all-clear signal when a threat or danger has passed.

Whatever the meaning, it's certainly infectious.

In late summer, the rains bring a flush of colour to the prairies.

For the prairie dogs, it's been a pretty boring diet until now,

but sunflowers will provide a tasty treat.

Each sunflower seed has twice the number of calories

as a blade of grass, so they're vital to the prairie dog pups

as they fatten up for the winter.

Time to set up their final exams

and see how their vocabulary is shaping up.

Are they still babbling like babies, or talking like adults?

Out come the usual suspects.

SQUEAKING

That's wonderful. We've got a really distinct coyote call.

There's another one calling from across the colony.

OK, Bill, let's do the badger.

They're standing up where they're foraging and looking

to see where the badger is going, and that's different from the coyote.

For the coyote, they run to the lip of their burrow and stand there.

For the badger, they are a little bit more reluctant to

run to their burrow until they see which burrow the badger is going to.

The signs are all good.

They are at least reacting in the right way to the fake predators.

The pups seem to be in fine voice.

But have they learnt the proper words from the adults?

To find out, they must compare them with pup calls

from earlier in the year to see if they've changed.

So let's just play the call that we got from the pups for the badger...

-OK.

-..two months ago versus the calls that we got from them today.

Let's see if we can hear it.

SQUEAKING

Yeah, again, very non-structured calls early in the season

and highly structured calls later in the season.

Looking at this spectrogram, you really see the difference.

-You do.

-Very detailed in the adult call.

What we saw at the beginning of the season

was that the pups gave very non-specific, generic calls,

and now these same pups are giving highly structured calls.

So, clearly, the pups have learned in just two months

how to adapt their calls so that they sound the same as the adult calls.

Let's see the same thing with the coyote.

Yeah, let's do that for the coyote.

Here we go.

Wow.

Again non-specific, just squeaks versus a lot of acoustic structure.

That's really very impressive.

-The calls are longer duration, as well.

-Yeah.

Probably because they contain a lot more information in them.

I think this shows that learning is actually going on,

because clearly we went from very generic,

non-specific calls to very specific calls in just a short period of time.

And I don't think that there's another explanation

other than learning.

It is possible that there is a genetic programme

that causes the maturation of the vocal tract,

but I think that's relatively unlikely

compared to the possibility of learning.

It's a eureka moment for Con and for the prairie dogs.

They have passed all the language tests with flying colours.

For Con, these findings are more than just about science.

He hopes they'll make people look differently at prairie dogs

and not see them as just vermin.

Prairie dogs have a very complicated social system.

They have to have some sense of their relationships between each other

in order to maintain this social system.

They also have this complex language,

and they have to have some kind of intellectual structure

in order to be able to understand this language, as well.

So the two things combined says to us that prairie dogs

are really very complex animals.

After 30 years of research, Con has all the information he needs

to help prove his bold claim that prairie dogs

have the most sophisticated language in the animal world.

At last the prairie dogs can step from the shadow of the bison

and take centre stage as the true hero of the prairies.

And they have one man to thank for that.