Natural World (1983) s29e12 Episode Script
Prairie Dogs: Talk of the Town
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.
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.
Let me stop it at this point.
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 individual 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 The second experiment isn't quite ready.
Bill and Patricia need to apply the finishing touches.
We got this badger off of eBay, and he was a completely prepared skin, except he didn't have any stuffing inside of him.
So, actually, what we're doing now is we're placing stuffing in him to give him shape.
Like most Americans, when I first knew about prairie dogs I didn't know much about them.
I thought they were just rodents, you know, bottom line.
Now I've learned that after, you know, thousands of years of evolution, they're an incredibly complex social animal, and every day I work with them I learn more and more and more and realise how little I actually know about them, especially in their communication and social interactions.
And there you go, all ready to hunt prairie dog.
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.
The eBay badger has done all it can.
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.
Let me play these calls for you.
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.
Breakfast isn't particularly exciting.
It's the same as lunch and dinner - grass.
Occasionally, an adventurous prairie dog will opt for something a bit more daring.
The size of a prairie dog territory will depend on the quality of the local grass.
But even where prairie dog numbers are high, there's usually enough for other animals.
The prairie dogs are about to have their breakfast rudely interrupted.
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.
It makes our language seem a bit long-winded.
Why use ten words when you could just say it all in one chirp? 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.
Even the bison, the largest animal on the prairies, benefits from having prairie dogs as neighbours.
And it's not just because their burrows are a convenient place to have a good scratch.
When people think of the American prairie, they usually think of the bison.
Historically, there were about 30 to 60 million bison prior to 1800.
But they tend not to think of prairie dogs, where historically there were five billion prairie dogs, co-existing very nicely with the bison.
And the prairie dogs were the ecological engine that tended to drive the prairie ecosystem.
They would clip vegetation, and as the vegetation would re-sprout, this was very nutritious for the bison and other large herbivores.
And the burrows of the prairie dogs provided refuges for hundreds of animal species.
So bison and prairie dogs and other species in the prairie ecosystem co-existed very nicely for thousands of years.
So for the bison, the cropped grass that re-grows around a prairie dog burrow is lush.
The prairie dog should be the hero of the prairies.
After all, without them the prairies as we know them would vanish.
But humans have somehow turned them into villains, and we like to kill our villains.
For the last couple of hundred years, human settlers have waged a war against the prairie dog.
As the Wild West was tamed and prairie turned over to ranching, a finger of blame was pointed at the prairie dog.
It was labelled a thief, falsely accused of stealing the best grass.
A bounty was placed on its head.
Shooting was one option.
Pumping sulphur smoke into their burrows was a more hazardous alternative.
But it was a government programme of mass poisoning with strychnine-laced feed that had the biggest impact on prairie dogs.
The land was being tamed for cattle, and there was no room for vermin.
In little more than a hundred years, their numbers dropped by a staggering 98%.
And by killing prairie dogs, humans were slowly killing the whole prairie.
Only recently have we come to recognise that without prairie dogs the prairies would be lost forever.
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.
Con and Patricia split up to try and find a good gathering of pups.
It's not long before their efforts pay off.
But what are they doing? This morning, we saw two juveniles frantically just shoving grass in their mouth.
All they think about is bedding and shoving it in their mouth.
They come to the lip of the burrow and then just kind of look out, and they go back in and they actually take all these grasses and stick them in their burrow.
Perhaps the pups learn from their parents how to collect bedding for their burrows.
Keeping a tidy room is all part of growing up.
But there's time between chores to relax and have fun.
All this play isn't helping Con and his team with their research.
They need to focus the pups' minds on something more serious.
Bill is setting up an experiment with a new fake predator.
But what on earth is it? 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.
Not a squeak from the young pups.
First time wasn't as successful as we'd hoped for, so we're going to try this again.
Now, come on, class, pay attention.
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.
OK, it's a failure, but let's not get in a negative state of mind.
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.
In other areas, prairie dogs often come face to face with the real thing.
Ferruginous hawks love to catch prairie dogs, especially when they have hungry youngsters to feed.
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.
This one's Rita.
Hi, Rita.
And then we have Izzy over here.
Hi, Izzy.
They're half-sisters.
Wonderful dogs.
Oh, you want to be petted.
And when they're not chewing on each other, they like to go after varmints like prairie dogs! So, can we let the dogs out? You bet.
Super.
Come here, Izzy.
Come here, Rita.
Come here, Rita.
OK, go get 'em.
Look at them go.
Yeah.
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.
As the summer draws on, Con keeps an eye on the young prairie dogs' progress.
He needs to find the right moment to test them again.
With a change in season just round the corner, the last thing on the pups' minds is passing a language test.
They need to make the most of what the prairie has to offer.
There is just one major obstacle to Con and the prairie dogs - the monsoons.
July and August are the wettest months of the year, and prairie dogs are often forced to retreat underground.
All that hard work building their elaborate burrow system has paid off.
They can keep nice and dry while the rest of the prairie gets soaked.
But too many days spent underground is valuable feeding time going to waste.
Might as well have a little nibble of your bed to keep hunger at bay.
During the heaviest of rains, prairie dogs can end up trapped below ground for days.
Eventually, the sun returns to the prairie, and the pups are the first above ground.
Patricia is keen to find out how this year's pups are doing.
But her presence is making someone very unhappy.
SQUEAKING There's an individual over there calling randomly for us.
In the field they actually call those Nervous Nellys or Worried Willys.
They really aren't important in the colony per se.
Some of the individuals will stand up and actually take notice of this caller, but they really won't pay attention.
It's kind of like the boy who cried wolf too many times.
After a while, they just stop believing this guy.
So he's really just a nuisance when we're doing field work, because we're really not sure what he's calling for.
But he just keeps going on and on and on and on.
Crying wolf isn't good for anyone.
You might not take notice when real danger threatens, and that could be a big mistake.
A prairie rattlesnake is taking an afternoon slither through prairie dog town.
The pups have been resting during the heat of the day.
This isn't the time to take a nap, not when a rattlesnake is on the search for a burrow and perhaps even a snack.
A call meaning, "Wake up!" would be really handy in this situation.
SQUEAKING It's looking a bit dicey for this little chap.
But let's not forget, prairie dog burrows have more than one way in and one way out.
It's a cool last-minute getaway, leaving the snake hungry, but at least it's found somewhere to shelter.
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.
It's getting late in the season.
Con, Bill and Patricia must get on with their final experiments before the first fall of snow.
Adult prairie dogs have already gone below ground for winter, but the pups still need to carry on fattening up.
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 really do.
Very detailed in the adult call.
Yeah, very detailed.
And again, look at how the structure goes up and then there's kind of a little drop and a little platform and then it drops down again, compared to just going up and down in frequencies here.
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, that should be interesting.
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.
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.
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.
Let me stop it at this point.
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 individual 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 The second experiment isn't quite ready.
Bill and Patricia need to apply the finishing touches.
We got this badger off of eBay, and he was a completely prepared skin, except he didn't have any stuffing inside of him.
So, actually, what we're doing now is we're placing stuffing in him to give him shape.
Like most Americans, when I first knew about prairie dogs I didn't know much about them.
I thought they were just rodents, you know, bottom line.
Now I've learned that after, you know, thousands of years of evolution, they're an incredibly complex social animal, and every day I work with them I learn more and more and more and realise how little I actually know about them, especially in their communication and social interactions.
And there you go, all ready to hunt prairie dog.
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.
The eBay badger has done all it can.
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.
Let me play these calls for you.
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.
Breakfast isn't particularly exciting.
It's the same as lunch and dinner - grass.
Occasionally, an adventurous prairie dog will opt for something a bit more daring.
The size of a prairie dog territory will depend on the quality of the local grass.
But even where prairie dog numbers are high, there's usually enough for other animals.
The prairie dogs are about to have their breakfast rudely interrupted.
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.
It makes our language seem a bit long-winded.
Why use ten words when you could just say it all in one chirp? 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.
Even the bison, the largest animal on the prairies, benefits from having prairie dogs as neighbours.
And it's not just because their burrows are a convenient place to have a good scratch.
When people think of the American prairie, they usually think of the bison.
Historically, there were about 30 to 60 million bison prior to 1800.
But they tend not to think of prairie dogs, where historically there were five billion prairie dogs, co-existing very nicely with the bison.
And the prairie dogs were the ecological engine that tended to drive the prairie ecosystem.
They would clip vegetation, and as the vegetation would re-sprout, this was very nutritious for the bison and other large herbivores.
And the burrows of the prairie dogs provided refuges for hundreds of animal species.
So bison and prairie dogs and other species in the prairie ecosystem co-existed very nicely for thousands of years.
So for the bison, the cropped grass that re-grows around a prairie dog burrow is lush.
The prairie dog should be the hero of the prairies.
After all, without them the prairies as we know them would vanish.
But humans have somehow turned them into villains, and we like to kill our villains.
For the last couple of hundred years, human settlers have waged a war against the prairie dog.
As the Wild West was tamed and prairie turned over to ranching, a finger of blame was pointed at the prairie dog.
It was labelled a thief, falsely accused of stealing the best grass.
A bounty was placed on its head.
Shooting was one option.
Pumping sulphur smoke into their burrows was a more hazardous alternative.
But it was a government programme of mass poisoning with strychnine-laced feed that had the biggest impact on prairie dogs.
The land was being tamed for cattle, and there was no room for vermin.
In little more than a hundred years, their numbers dropped by a staggering 98%.
And by killing prairie dogs, humans were slowly killing the whole prairie.
Only recently have we come to recognise that without prairie dogs the prairies would be lost forever.
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.
Con and Patricia split up to try and find a good gathering of pups.
It's not long before their efforts pay off.
But what are they doing? This morning, we saw two juveniles frantically just shoving grass in their mouth.
All they think about is bedding and shoving it in their mouth.
They come to the lip of the burrow and then just kind of look out, and they go back in and they actually take all these grasses and stick them in their burrow.
Perhaps the pups learn from their parents how to collect bedding for their burrows.
Keeping a tidy room is all part of growing up.
But there's time between chores to relax and have fun.
All this play isn't helping Con and his team with their research.
They need to focus the pups' minds on something more serious.
Bill is setting up an experiment with a new fake predator.
But what on earth is it? 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.
Not a squeak from the young pups.
First time wasn't as successful as we'd hoped for, so we're going to try this again.
Now, come on, class, pay attention.
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.
OK, it's a failure, but let's not get in a negative state of mind.
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.
In other areas, prairie dogs often come face to face with the real thing.
Ferruginous hawks love to catch prairie dogs, especially when they have hungry youngsters to feed.
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.
This one's Rita.
Hi, Rita.
And then we have Izzy over here.
Hi, Izzy.
They're half-sisters.
Wonderful dogs.
Oh, you want to be petted.
And when they're not chewing on each other, they like to go after varmints like prairie dogs! So, can we let the dogs out? You bet.
Super.
Come here, Izzy.
Come here, Rita.
Come here, Rita.
OK, go get 'em.
Look at them go.
Yeah.
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.
As the summer draws on, Con keeps an eye on the young prairie dogs' progress.
He needs to find the right moment to test them again.
With a change in season just round the corner, the last thing on the pups' minds is passing a language test.
They need to make the most of what the prairie has to offer.
There is just one major obstacle to Con and the prairie dogs - the monsoons.
July and August are the wettest months of the year, and prairie dogs are often forced to retreat underground.
All that hard work building their elaborate burrow system has paid off.
They can keep nice and dry while the rest of the prairie gets soaked.
But too many days spent underground is valuable feeding time going to waste.
Might as well have a little nibble of your bed to keep hunger at bay.
During the heaviest of rains, prairie dogs can end up trapped below ground for days.
Eventually, the sun returns to the prairie, and the pups are the first above ground.
Patricia is keen to find out how this year's pups are doing.
But her presence is making someone very unhappy.
SQUEAKING There's an individual over there calling randomly for us.
In the field they actually call those Nervous Nellys or Worried Willys.
They really aren't important in the colony per se.
Some of the individuals will stand up and actually take notice of this caller, but they really won't pay attention.
It's kind of like the boy who cried wolf too many times.
After a while, they just stop believing this guy.
So he's really just a nuisance when we're doing field work, because we're really not sure what he's calling for.
But he just keeps going on and on and on and on.
Crying wolf isn't good for anyone.
You might not take notice when real danger threatens, and that could be a big mistake.
A prairie rattlesnake is taking an afternoon slither through prairie dog town.
The pups have been resting during the heat of the day.
This isn't the time to take a nap, not when a rattlesnake is on the search for a burrow and perhaps even a snack.
A call meaning, "Wake up!" would be really handy in this situation.
SQUEAKING It's looking a bit dicey for this little chap.
But let's not forget, prairie dog burrows have more than one way in and one way out.
It's a cool last-minute getaway, leaving the snake hungry, but at least it's found somewhere to shelter.
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.
It's getting late in the season.
Con, Bill and Patricia must get on with their final experiments before the first fall of snow.
Adult prairie dogs have already gone below ground for winter, but the pups still need to carry on fattening up.
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 really do.
Very detailed in the adult call.
Yeah, very detailed.
And again, look at how the structure goes up and then there's kind of a little drop and a little platform and then it drops down again, compared to just going up and down in frequencies here.
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, that should be interesting.
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.