0:00:16 > 0:00:21The North American prairies, home to the bison.
0:00:23 > 0:00:25But this film isn't about the bison.
0:00:25 > 0:00:29It's about a tiny creature that lives beneath the bison's feet...
0:00:32 > 0:00:35..the prairie dog.
0:00:36 > 0:00:39You might easily overlook the prairie dog,
0:00:39 > 0:00:41until it opens its mouth.
0:00:41 > 0:00:43SQUEAKING
0:00:43 > 0:00:49It's a little animal with a big voice.
0:00:49 > 0:00:52A team of scientists believe this noise
0:00:52 > 0:00:55is in fact a very complex language,
0:00:55 > 0:01:00which is remarkable for an animal many see as lowly vermin.
0:01:01 > 0:01:04So, what are they saying?
0:01:04 > 0:01:10To find out, scientists have devised a set of cunning experiments.
0:01:13 > 0:01:19But could these barks, squeaks and chirps really be a language?
0:01:31 > 0:01:36To our human ears, this just sounds like a lot of unnecessary noise,
0:01:36 > 0:01:42but to other prairie dogs it's all part of a jolly good conversation.
0:01:42 > 0:01:44That is, if you believe this man,
0:01:44 > 0:01:48prairie dog expert Professor Con Slobodchikoff.
0:01:48 > 0:01:53Prairie dogs have the most complex natural language
0:01:53 > 0:01:55that's been decoded so far.
0:01:55 > 0:01:59They have words for different predators, they have
0:01:59 > 0:02:05descriptive words for describing the individual features of predators,
0:02:05 > 0:02:10so it's a pretty complex language that has a lot of elements.
0:02:10 > 0:02:12A relative of the squirrel
0:02:12 > 0:02:16with a language second only to humans in its complexity?
0:02:16 > 0:02:19That's a bold claim.
0:02:19 > 0:02:21But Con has a problem.
0:02:21 > 0:02:25He's fighting an in-built prejudice against these little rodents.
0:02:25 > 0:02:29Convincing the wider world that prairie dogs are great linguists
0:02:29 > 0:02:32is proving a tough challenge.
0:02:32 > 0:02:35He believes if we just get to know them a little better,
0:02:35 > 0:02:41understand their world, then we might just see his point of view.
0:02:41 > 0:02:45Life as a prairie dog is complicated.
0:02:45 > 0:02:47It's not just a simple matter
0:02:47 > 0:02:50of eating grass and minding your own business.
0:02:52 > 0:02:55You have to share your space with lots of other prairie dogs.
0:02:57 > 0:03:02Every prairie dog is part of a big community called a town.
0:03:04 > 0:03:08The largest prairie dog towns stretch over tens of miles,
0:03:08 > 0:03:12their excavated homes pockmarking the prairie landscape.
0:03:15 > 0:03:19Living together requires impeccable social skills.
0:03:19 > 0:03:23Kissing is all the rage in prairie dog town.
0:03:23 > 0:03:25A little taste of saliva
0:03:25 > 0:03:28is like a calling card that helps identify a visitor.
0:03:30 > 0:03:33Prairie dogs, though, are nervous creatures,
0:03:33 > 0:03:36always on the lookout for signs of trouble across town.
0:03:38 > 0:03:41But what is there to worry about?
0:03:43 > 0:03:47Prairie dogs aren't the only animals living in the town.
0:03:49 > 0:03:53Squatters have moved into some of their vacant burrows.
0:04:01 > 0:04:05All these strangers make prairie dogs a little nervous.
0:04:05 > 0:04:07And so they should be.
0:04:08 > 0:04:12Prairie dogs are under attack from all quarters.
0:04:12 > 0:04:15There are times when they must feel besieged
0:04:15 > 0:04:16by animals that want to eat them.
0:04:18 > 0:04:21Even when they retreat to their underground burrows,
0:04:21 > 0:04:23the prairie dogs can't really relax.
0:04:35 > 0:04:40With no safety anywhere, above or below ground, prairie dogs
0:04:40 > 0:04:43have come up with a clever strategy for dealing with these threats.
0:04:43 > 0:04:45LOUD SQUEAKING
0:04:45 > 0:04:47They shout.
0:04:47 > 0:04:50Very loudly.
0:04:50 > 0:04:55Technically speaking, it's an alarm call.
0:04:58 > 0:05:01You might still be wondering why Con would choose
0:05:01 > 0:05:04such a humble subject to study animal language.
0:05:04 > 0:05:07After all, there are more likely animal linguists -
0:05:07 > 0:05:10whales or monkeys.
0:05:10 > 0:05:14But there was something about those prairie dog alarm calls
0:05:14 > 0:05:17that piqued his interest.
0:05:17 > 0:05:20With so many predators living in prairie dog town, Con wondered,
0:05:20 > 0:05:23do the prairie dogs have just one call,
0:05:23 > 0:05:27or do they have different calls for the different predators?
0:05:27 > 0:05:30There's only one way to find out.
0:05:30 > 0:05:34Con must test their calls.
0:05:34 > 0:05:39He's on his way to a remote ranch in the north of New Mexico.
0:05:39 > 0:05:42It's a haven for prairie dogs.
0:05:42 > 0:05:46Two species live here, Gunnison's and black-tails.
0:05:46 > 0:05:49Joining him are two of his students, Patricia Dennis,
0:05:49 > 0:05:51who will help record the calls,
0:05:51 > 0:05:55and Bill Briggs, who's devised a series of experiments
0:05:55 > 0:05:57to test the prairie dogs.
0:06:00 > 0:06:03Together, this team hopes to show once and for all
0:06:03 > 0:06:07that we have underestimated the little prairie dog.
0:06:18 > 0:06:23First of all, Con looks for signs of predators in his research area.
0:06:23 > 0:06:24Here's a badger excavation.
0:06:24 > 0:06:26This is very fresh.
0:06:26 > 0:06:29It probably happened in the last day or two.
0:06:29 > 0:06:32This is the way that badgers typically hunt.
0:06:32 > 0:06:35They'll excavate a prairie dog burrow and then go inside,
0:06:35 > 0:06:37and while the prairie dogs are sleeping,
0:06:37 > 0:06:39they will eat the prairie dogs
0:06:39 > 0:06:42and then they'll also sleep inside the burrow.
0:06:42 > 0:06:45They typically excavate a number of burrows
0:06:45 > 0:06:48all around us in a particular area, and then they move on
0:06:48 > 0:06:51to another place once they've eaten all the prairie dogs
0:06:51 > 0:06:54that live in a particular burrow system.
0:06:57 > 0:07:00The presence of predators is welcome news for Con.
0:07:00 > 0:07:04The prairie dogs should be on a state of alert,
0:07:04 > 0:07:06and that'll mean good alarm calls.
0:07:06 > 0:07:08SQUEAKING
0:07:08 > 0:07:13But waiting for predators to appear would be far too time-consuming.
0:07:13 > 0:07:16These imaginative scientists have a solution -
0:07:16 > 0:07:17they bring their own.
0:07:34 > 0:07:38Time to set up the first experiment.
0:07:39 > 0:07:42Bill must keep the dummy predator under wraps
0:07:42 > 0:07:44while he finds a suitable spot.
0:07:46 > 0:07:50Some prairie dogs are already a little spooked.
0:08:06 > 0:08:09Con uses his car as a screen to hide behind.
0:08:09 > 0:08:11It's important that no-one is visible.
0:08:15 > 0:08:18The predator is revealed...
0:08:21 > 0:08:24..a plastic coyote without any legs.
0:08:29 > 0:08:31It seems like an encouraging result.
0:08:31 > 0:08:33The prairie dogs are certainly being vocal.
0:08:36 > 0:08:42What's really wonderful about this is that other individuals are chiming in
0:08:42 > 0:08:44just in response to the vocalisation,
0:08:44 > 0:08:47so they don't even have to see the stimulus
0:08:47 > 0:08:50in order to know that this is a coyote, and they start yelling.
0:08:52 > 0:08:56Every call recorded must subsequently be analysed by Con.
0:08:56 > 0:08:59We can hear the difference in the calls
0:08:59 > 0:09:03between the different predators, but that's not really enough for us.
0:09:03 > 0:09:07What we really need is some sort of analytical tools
0:09:07 > 0:09:11for measuring what the frequency and time elements in the call are.
0:09:11 > 0:09:15And so this software here allows us to do this.
0:09:17 > 0:09:21This is our alarm call elicited for a coyote,
0:09:21 > 0:09:26and we can hear that it has a series of rhythmic chirps.
0:09:26 > 0:09:28We think that each prairie dog
0:09:28 > 0:09:31has its own individual, unique tonal qualities,
0:09:31 > 0:09:36just like humans have different voices and different voice prints.
0:09:36 > 0:09:39But even though each individual prairie dog might differ,
0:09:39 > 0:09:41all the prairie dogs have a common call
0:09:41 > 0:09:46for a coyote even within those individual voice print differences.
0:09:46 > 0:09:49So we think that when a prairie dog is calling for a coyote,
0:09:49 > 0:09:53they probably know who the prairie dog is that's calling,
0:09:53 > 0:09:57just the same way that we can on the telephone hear somebody's voice
0:09:57 > 0:10:01and immediately recognise it as a person that we know.
0:10:01 > 0:10:02SQUEAKY CHIRPING
0:10:05 > 0:10:09Everything is ready for experiment number two, the stuffed badger.
0:10:18 > 0:10:22Con and his team are very excited by this one.
0:10:22 > 0:10:24This is the first time they've ever tested a badger.
0:10:26 > 0:10:30Will the prairie dogs have a specific alarm call for it?
0:10:40 > 0:10:42The badger's out.
0:10:42 > 0:10:45LOUD SQUEAKING
0:10:55 > 0:10:58Well, the prairie dogs are certainly calling,
0:10:58 > 0:11:03but are these calls different from the earlier ones to the coyote?
0:11:03 > 0:11:05Con hopes so.
0:11:07 > 0:11:10Now the researchers must take a look at all the recordings
0:11:10 > 0:11:12from today's experiments.
0:11:12 > 0:11:14The badger call is an entirely new call for us.
0:11:14 > 0:11:17We've never recorded a call for a badger.
0:11:17 > 0:11:21So it's really exciting to look at the structure of this call
0:11:21 > 0:11:22and see what it looks like.
0:11:22 > 0:11:24And it looks very different
0:11:24 > 0:11:27from any of the other calls that we've recorded.
0:11:27 > 0:11:28SQUEAKING
0:11:30 > 0:11:32SQUEAKING
0:11:35 > 0:11:37HIGHER-PITCHED SQUEAKING
0:11:37 > 0:11:42To Con's expert ears and eyes, there is a difference both in their calls
0:11:42 > 0:11:45and in the shape of their sound graphs.
0:11:49 > 0:11:51The shape of each sound curve
0:11:51 > 0:11:54varies subtly, but is consistent for each predator.
0:12:00 > 0:12:03But to convince any would-be doubters,
0:12:03 > 0:12:05Con has another experiment planned.
0:12:08 > 0:12:11Over his 30 years of research, he's noticed that prairie dogs
0:12:11 > 0:12:16react in different ways to different predators.
0:12:16 > 0:12:19If the alarm calls for coyote and badger do indeed differ,
0:12:19 > 0:12:21then playing back the two calls
0:12:21 > 0:12:27to a group of prairie dogs should produce distinct responses.
0:12:27 > 0:12:29Bill's big speakers get fired up.
0:12:29 > 0:12:31HIGH-PITCHED SQUEAKING
0:12:32 > 0:12:36First, the alarm call for coyote.
0:12:36 > 0:12:39The prairie dogs react instantly.
0:12:47 > 0:12:50Having spooked one part of the colony with the loudest
0:12:50 > 0:12:53alarm call they've ever heard,
0:12:53 > 0:12:56the team moves on to an undisturbed spot
0:12:56 > 0:13:00to try out their second alarm call, the badger.
0:13:04 > 0:13:05SQUEAKING
0:13:09 > 0:13:12The reaction is very different.
0:13:19 > 0:13:22We had a terrific response, and for the coyote call
0:13:22 > 0:13:25they did just what they're supposed to do for a coyote.
0:13:25 > 0:13:30They ran to the burrows and stood at the lip of the burrows and watched.
0:13:30 > 0:13:32For the badger call, they ran to the lip of the burrows
0:13:32 > 0:13:36and crouched down, just like they're supposed to for a badger.
0:13:36 > 0:13:38So it was a terrific result.
0:13:38 > 0:13:42Adopting different tactics for different predators
0:13:42 > 0:13:43makes perfect sense.
0:13:43 > 0:13:46A coyote will hunt by surprise,
0:13:46 > 0:13:51so perhaps it's safest to sit up and keep an eye on it at all times.
0:13:53 > 0:13:56Badgers are the bulldozers of the predator world.
0:13:56 > 0:14:00They will dig into a prairie dog hole.
0:14:00 > 0:14:03Crouching down might be a way of hiding yourself
0:14:03 > 0:14:05so the badger doesn't choose your burrow.
0:14:15 > 0:14:17It's been a good day for the team.
0:14:17 > 0:14:20Every new alarm call is a new addition
0:14:20 > 0:14:23to their dictionary of prairie dog words.
0:14:25 > 0:14:27But there's still a long way to go
0:14:27 > 0:14:32in their quest to prove that prairie dogs have a complex language.
0:14:49 > 0:14:53It's early morning, and the prairie dogs are already up.
0:14:57 > 0:15:01Con and his team are back, and they're keen to try a new test,
0:15:01 > 0:15:05one that's a lot stranger than their earlier experiments.
0:15:08 > 0:15:12Con has a hunch that prairie dogs have unique calls for colours.
0:15:19 > 0:15:23It sounds a bit mad, but he's putting it to the test.
0:15:24 > 0:15:28(Patricia here's doing a coloured shirt experiment.
0:15:28 > 0:15:32(The idea here is to test the ability of the prairie dogs
0:15:32 > 0:15:35(to discriminate between different colours
0:15:35 > 0:15:39(and how they incorporate that information into their alarm calls.)
0:15:43 > 0:15:47No joy. The prairie dogs aren't calling.
0:15:50 > 0:15:55(I think one problem is that Patricia's not threatening enough.
0:15:55 > 0:15:59(She tends to walk slowly and is kind of relaxed about it.
0:15:59 > 0:16:01(I wonder if we could get Bill to wear a shirt.)
0:16:03 > 0:16:06Time to substitute Bill for Patricia.
0:16:09 > 0:16:11Bill's manly walk provokes a response.
0:16:11 > 0:16:13SQUEAKING
0:16:14 > 0:16:18But behind this quirky experiment is a bigger question.
0:16:18 > 0:16:22Could the prairie dog calls actually contain more information
0:16:22 > 0:16:24than just the identity of the threat?
0:16:24 > 0:16:28Could they be describing precisely what they see?
0:16:28 > 0:16:30Con believes the answer is yes.
0:16:32 > 0:16:36Throughout his 30-year study, he's found that changing the speed,
0:16:36 > 0:16:39direction and even the colour of a threat
0:16:39 > 0:16:42results in a change in the prairie dogs' alarm call.
0:16:46 > 0:16:50We think that each one of these chirps contains a noun-like word
0:16:50 > 0:16:53and it also contains adjective-like words,
0:16:53 > 0:16:57which describe the colour, the size, and all of that is
0:16:57 > 0:17:00put together into one of these single chirps,
0:17:00 > 0:17:04pretty much the same way that we would put together a sentence.
0:17:04 > 0:17:11So, we might say, "A tall, skinny coyote with yellow fur,"
0:17:11 > 0:17:17and the prairie dogs manage to put all of this into a single chirp.
0:17:17 > 0:17:21In other words, prairie dogs can cram into one short call
0:17:21 > 0:17:25the same amount of information found in a human sentence.
0:17:25 > 0:17:27How do they do it?
0:17:27 > 0:17:32Con suspects the answer lies in the fine detail of their calls.
0:17:33 > 0:17:39Each alarm call or each chirp is a series of stacked harmonics,
0:17:39 > 0:17:42that you can see one on top of the other,
0:17:42 > 0:17:46but instead of being actual multiples of the base frequency,
0:17:46 > 0:17:51they're actually modulated by the vocal apparatus of the prairie dog,
0:17:51 > 0:17:55and that's what contains the information that this is a coyote
0:17:55 > 0:17:58as well as the general colour and size and shape of the coyote.
0:18:00 > 0:18:04So prairie dogs can subtly alter the meaning of their chirp
0:18:04 > 0:18:06by varying each harmonic.
0:18:08 > 0:18:11It's an amazing way of tightly packaging information.
0:18:15 > 0:18:17All these findings demonstrate
0:18:17 > 0:18:20this is an animal we have grossly underestimated,
0:18:20 > 0:18:25that the prairie dog is much more complex than we thought.
0:18:25 > 0:18:27This is no surprise to the man
0:18:27 > 0:18:30who has doggedly championed prairie dogs his entire career.
0:18:33 > 0:18:38Everything about prairie dogs points to them being complex animals -
0:18:38 > 0:18:39even their homes.
0:18:41 > 0:18:42This is a prairie dog hole.
0:18:42 > 0:18:48It is part of an elaborate burrow system that is underground.
0:18:48 > 0:18:53The hole goes down maybe about between one and three metres,
0:18:53 > 0:18:55and then the entire burrow system
0:18:55 > 0:19:00stretches out for anywhere between three and five metres,
0:19:00 > 0:19:03with a fairly elaborate structure.
0:19:03 > 0:19:06There's a bathroom chamber where they pee and poop
0:19:06 > 0:19:09and there's a nest chamber where they sleep.
0:19:11 > 0:19:15There's also side chambers, where one prairie dog coming down
0:19:15 > 0:19:18meets another prairie dog coming up,
0:19:18 > 0:19:20and one of them backs into a side chamber
0:19:20 > 0:19:22so that the other one can go past,
0:19:22 > 0:19:26just like two cars on a narrow, winding mountain road.
0:19:29 > 0:19:31The prairie dog burrow system
0:19:31 > 0:19:34is remarkably sophisticated in its engineering.
0:19:34 > 0:19:37These rodents can excavate an extensive
0:19:37 > 0:19:41tunnel network that connects as many as six entrance holes.
0:19:48 > 0:19:52And it's deep underground where the pups are born in spring.
0:19:56 > 0:20:01Blind and without fur, they huddle together for warmth and security.
0:20:04 > 0:20:08This underground world of prairie dogs is rarely observed.
0:20:30 > 0:20:31It will be five weeks
0:20:31 > 0:20:35before the pups are ready to leave their nursery chamber.
0:20:35 > 0:20:38When that moment arrives, Con will be there.
0:20:38 > 0:20:42The pup calls will be crucial to his work.
0:20:48 > 0:20:50Above ground, the mounds are designed
0:20:50 > 0:20:55to funnel rain away from the holes and so keep their burrows dry.
0:20:57 > 0:20:59The hard work by these mining rodents
0:20:59 > 0:21:01has created a vast infrastructure
0:21:01 > 0:21:05that makes the prairies attractive for other animals.
0:21:06 > 0:21:09Many different species of all shapes and sizes
0:21:09 > 0:21:12have come to rely on prairie dogs for their lodging.
0:21:17 > 0:21:22Only recently have we come to recognise that without prairie dogs,
0:21:22 > 0:21:24the prairies would be lost for ever.
0:21:24 > 0:21:29They're important to all life on the prairies,
0:21:29 > 0:21:35including lots of animals that want to eat them.
0:21:35 > 0:21:40Con believes this relationship with other animals is the main reason
0:21:40 > 0:21:44why prairie dogs have developed a complex language.
0:21:44 > 0:21:48So what happens to the language if you take away all the predators?
0:21:50 > 0:21:54There's only one place where he can find the answer to that...
0:21:58 > 0:22:01..at a zoo.
0:22:05 > 0:22:09These prairie dogs have been in captivity all their lives.
0:22:09 > 0:22:11They've never seen predators.
0:22:20 > 0:22:24So what will happen when Bill and Patricia introduce
0:22:24 > 0:22:26their dummy predators?
0:22:30 > 0:22:32Will these captive prairie dogs
0:22:32 > 0:22:35have a call for threats they've never seen before?
0:22:42 > 0:22:46The coyote makes its entrance.
0:22:50 > 0:22:52SQUEAKING
0:22:53 > 0:22:55Well, they're certainly calling.
0:22:55 > 0:22:58But are they saying, "Coyote"?
0:22:58 > 0:23:02Right now, we've got about eight mics in here to make sure that we've got
0:23:02 > 0:23:05no problems with echoes or any other aberrations,
0:23:05 > 0:23:08and we're recording the prairie dogs' call to a coyote.
0:23:08 > 0:23:12And I'm watching here on the computer screen to look at the spectrograph
0:23:12 > 0:23:16to see how it's formed. And to tell you the truth,
0:23:16 > 0:23:19it's completely different than what we're used to.
0:23:19 > 0:23:23We still have individual chirps, but they have no definition to them.
0:23:23 > 0:23:27They're completely different, and it's really surprising to see.
0:23:27 > 0:23:29They're making a noise,
0:23:29 > 0:23:32but it doesn't sound like a prairie dog word.
0:23:34 > 0:23:37Now it's the badger's turn.
0:23:42 > 0:23:45Is he doing anything or just looking at it?
0:23:45 > 0:23:47There's two prairie dogs right now calling.
0:23:47 > 0:23:49There's one calling at the badger
0:23:49 > 0:23:52and another prairie dog by the metal grate.
0:23:55 > 0:23:58I've got a badger sitting out there,
0:23:58 > 0:24:01and we've got two prairie dogs calling for it.
0:24:01 > 0:24:03And the spectrograph is just amazing.
0:24:03 > 0:24:06It's nothing like we've seen before.
0:24:06 > 0:24:09We've got the chevrons, but there's no structure to them.
0:24:10 > 0:24:13Their calls are like a scream.
0:24:13 > 0:24:15It's an alarm, but without any meaning.
0:24:15 > 0:24:18It suggests they only develop their words
0:24:18 > 0:24:21after repeated exposure to predators.
0:24:23 > 0:24:25If so, that's learning,
0:24:25 > 0:24:29and that's a key characteristic of a proper language.
0:24:32 > 0:24:35Bill and Patricia's results from the zoo
0:24:35 > 0:24:40show that animals who have been in a zoo setting for at least nine years,
0:24:40 > 0:24:43who have not heard any predator calls,
0:24:43 > 0:24:49probably lose their predator calls or lose the ability to make those calls.
0:24:49 > 0:24:54The zoo animals have very non-specific noise-like calls,
0:24:54 > 0:24:58and so I think that this shows that learning is important
0:24:58 > 0:25:00in this animal language.
0:25:00 > 0:25:02This is a major discovery.
0:25:02 > 0:25:06Learning is a crucial element of every language.
0:25:06 > 0:25:09But can Con build on the zoo results
0:25:09 > 0:25:13and demonstrate learning is taking place out on the prairies?
0:25:13 > 0:25:16If prairie dogs are learning their calls,
0:25:16 > 0:25:20then it must be happening once the pups come above ground.
0:25:20 > 0:25:25This, after all, is the first time they'll see other animals.
0:25:25 > 0:25:29Testing their ability to learn will be the most important experiment
0:25:29 > 0:25:34of all to prove that prairie dogs have a complex language.
0:25:34 > 0:25:39Con's reputation and the reputation of all prairie dogs
0:25:39 > 0:25:41now depends on the pups.
0:25:44 > 0:25:45In early June,
0:25:45 > 0:25:49the pups are just taking their very first steps above ground.
0:25:52 > 0:25:57Bill is setting up an experiment with a new fake predator.
0:26:06 > 0:26:11This is a silhouette of an airborne predator, like a hawk.
0:26:11 > 0:26:17And we'll shoot this down this line to try and simulate a hawk attacking
0:26:17 > 0:26:20a prairie dog in the colony, and it should be pretty exciting to see.
0:26:47 > 0:26:49Well, this is pretty disappointing.
0:26:49 > 0:26:52We've done this experiment before in the past,
0:26:52 > 0:26:54and the animals at other sites
0:26:54 > 0:26:58have given a characteristic hawk call and then they run to their burrows.
0:26:58 > 0:27:01But here, they just simply run to their burrows
0:27:01 > 0:27:02and they don't give a call.
0:27:02 > 0:27:05Maybe they don't see any aerial predators
0:27:05 > 0:27:07and so have no reason to give a hawk call.
0:27:07 > 0:27:11But nevertheless, it's really disappointing.
0:27:11 > 0:27:13Perhaps prairie dog pups are a lot cannier
0:27:13 > 0:27:15than we give them credit for.
0:27:15 > 0:27:20Maybe Bill's fake hawk wasn't quite realistic enough for them.
0:27:32 > 0:27:35This is more like it.
0:27:35 > 0:27:36A swooping hawk
0:27:36 > 0:27:40is enough to create a state of panic in prairie dog town.
0:27:47 > 0:27:50Many prairie dogs will go underground.
0:27:57 > 0:28:00If the aerial approach isn't successful,
0:28:00 > 0:28:03then the hawk has another strategy -
0:28:03 > 0:28:05just sit and wait.
0:28:11 > 0:28:13And wait.
0:28:15 > 0:28:19The one thing you don't want to do is go above ground,
0:28:19 > 0:28:22not when there's a big hawk outside.
0:28:22 > 0:28:27But pups can be a little impatient.
0:28:27 > 0:28:33A hawk can hold prairie dogs hostage like this for many hours.
0:28:33 > 0:28:37Both the prairie dogs and the hawk want to feed.
0:28:37 > 0:28:40It becomes a battle of wills.
0:29:03 > 0:29:05Eventually, the pups claim victory.
0:29:23 > 0:29:25Back at his study colony,
0:29:25 > 0:29:29Con is worried that there aren't as many predators as he thought,
0:29:29 > 0:29:32and that's making it difficult to record pup calls.
0:29:35 > 0:29:39He needs to get the colony on a higher state of alert,
0:29:39 > 0:29:42so he has a plan to stir things up a bit.
0:29:52 > 0:29:54- Hi, Brent.- Hey, Con. How you doing?
0:29:54 > 0:29:56- It's good to see you. - Good to see you.
0:29:56 > 0:29:58- So, these are your dogs? - Yeah, these are my two dogs.
0:29:58 > 0:30:01And when they're not chewing on each other,
0:30:01 > 0:30:03they like to go after varmints like prairie dogs!
0:30:08 > 0:30:11The purpose of this is to get the prairie dogs
0:30:11 > 0:30:14more used to having predators around.
0:30:14 > 0:30:18This colony probably has not had very much predation,
0:30:18 > 0:30:21and they aren't calling as much as I would like.
0:30:21 > 0:30:25And so having the dogs running around gets them more alert
0:30:25 > 0:30:28and gets them to call more for other stimuli,
0:30:28 > 0:30:31like some of the other experiments that we're going to do.
0:30:33 > 0:30:39This isn't the first time Con has introduced prairie dog to real dog.
0:30:39 > 0:30:43What we've found in the past is that they do recognise individual dogs.
0:30:43 > 0:30:46They can describe the shape of the dogs,
0:30:46 > 0:30:50the size of the dogs and the coat colour of the dogs.
0:30:50 > 0:30:53But have the dogs had the desired effect?
0:30:53 > 0:30:56Have they stirred up this colony?
0:30:56 > 0:31:00Only one way to find out.
0:31:14 > 0:31:19The pups seem to be on high alert, but will they call?
0:31:28 > 0:31:30Everything is in place.
0:31:30 > 0:31:33Now it's all down to the pups.
0:31:35 > 0:31:38The tension is becoming unbearable.
0:31:54 > 0:31:56SQUEAKING
0:31:57 > 0:32:00The plastic coyote has worked its magic again.
0:32:00 > 0:32:06But are the pups actually saying, "Coyote"?
0:32:06 > 0:32:10If, as Con suspects, the pups learn the alarm calls,
0:32:10 > 0:32:12then at this early stage of their lives,
0:32:12 > 0:32:16he wouldn't expect them to know the calls for different predators.
0:32:18 > 0:32:20Every call recorded
0:32:20 > 0:32:23will be subjected to stringent scientific analysis.
0:32:26 > 0:32:28Look at the difference.
0:32:28 > 0:32:32But at first glance, the findings look positive for Con.
0:32:32 > 0:32:35Now, he does have the same number of calls per series,
0:32:35 > 0:32:38it seems like, and the loudness and everything else is the same.
0:32:38 > 0:32:43And maybe the loudness and the number of calls is something that is innate,
0:32:43 > 0:32:45and maybe the structure is something...
0:32:45 > 0:32:49Side by side, the adult and pup calls are very different.
0:32:49 > 0:32:50SQUEAKING
0:32:50 > 0:32:52We have here a pup
0:32:52 > 0:32:55and an adult calling for the coyote.
0:32:55 > 0:32:57They sound very different,
0:32:57 > 0:33:01and they also look very different on the computer.
0:33:07 > 0:33:10We can see here the adult call has a lot of structure in it
0:33:10 > 0:33:13and it contains a lot of information.
0:33:13 > 0:33:17The pup call, on the other hand, doesn't have very much information
0:33:17 > 0:33:23in it and it changes in structure, just like babbling in little kids.
0:33:23 > 0:33:27So this pup is gradually acquiring more and more structure.
0:33:27 > 0:33:28As in any language,
0:33:28 > 0:33:32the youngsters must practise getting the words right.
0:33:32 > 0:33:35In human babies we call it babbling,
0:33:35 > 0:33:38and it appears that prairie dog babies babble, too,
0:33:38 > 0:33:41as they struggle to make the right call.
0:33:41 > 0:33:43These results are good news for Con,
0:33:43 > 0:33:47but they don't prove they're learning, not yet.
0:33:47 > 0:33:51To really show that, they'll need to test the same pups later in the year
0:33:51 > 0:33:55to see if their calls change over time.
0:33:55 > 0:33:58For now, there's nothing the team can do
0:33:58 > 0:33:59but wait for the pups to grow up.
0:33:59 > 0:34:04That is, if they're able to grow up.
0:34:06 > 0:34:11Prairie dog pups are an ideal snack for hungry predators.
0:34:13 > 0:34:16You might think the alarm calls of prairie dogs would make
0:34:16 > 0:34:19it particularly challenging for a predator to hunt them.
0:34:19 > 0:34:23But that doesn't seem to worry this family of swift foxes.
0:34:29 > 0:34:33They've made a home in a deserted prairie dog burrow
0:34:33 > 0:34:35right in the middle of a colony.
0:34:36 > 0:34:40The fox cubs aren't even attempting to keep a low profile.
0:34:42 > 0:34:45It's almost as if they're deliberately taunting
0:34:45 > 0:34:47their prairie dog neighbours.
0:34:54 > 0:34:59With four energetic cubs, Mum has a busy time.
0:34:59 > 0:35:02She must hunt regularly.
0:35:10 > 0:35:12When she goes out hunting,
0:35:12 > 0:35:15the prairie dogs soon sit up and take notice.
0:35:23 > 0:35:26But they're remarkably quiet.
0:35:26 > 0:35:29Alarm calls warn of a pending threat,
0:35:29 > 0:35:35but if that threat comes too close, prairie dogs will often fall silent.
0:35:35 > 0:35:38To call out now could prove fatal.
0:35:43 > 0:35:45If a pup does indeed learn from its parents,
0:35:45 > 0:35:48then knowing when to hold fire and retreat
0:35:48 > 0:35:51could be one of the most valuable lessons of its life...
0:36:00 > 0:36:03SQUEAKING
0:36:09 > 0:36:14..or the end of its life, if it gets it wrong.
0:36:21 > 0:36:23When one of your neighbours is killed,
0:36:23 > 0:36:29it wouldn't seem unreasonable to expect a moment of quiet reflection.
0:36:34 > 0:36:38But once the swift fox is out of sight,
0:36:38 > 0:36:43something quite extraordinary happens in prairie dog town.
0:36:43 > 0:36:46LOUD BARKING
0:36:46 > 0:36:50It looks like the prairie dogs are experiencing a moment of madness.
0:36:52 > 0:36:58This acrobatic display is in fact the jump-yip call.
0:36:58 > 0:37:05It could be an all-clear signal when a threat or danger has passed.
0:37:05 > 0:37:08Whatever the meaning, it's certainly infectious.
0:37:23 > 0:37:28In late summer, the rains bring a flush of colour to the prairies.
0:38:11 > 0:38:15For the prairie dogs, it's been a pretty boring diet until now,
0:38:15 > 0:38:20but sunflowers will provide a tasty treat.
0:38:21 > 0:38:24Each sunflower seed has twice the number of calories
0:38:24 > 0:38:28as a blade of grass, so they're vital to the prairie dog pups
0:38:28 > 0:38:30as they fatten up for the winter.
0:38:36 > 0:38:38Time to set up their final exams
0:38:38 > 0:38:41and see how their vocabulary is shaping up.
0:38:41 > 0:38:46Are they still babbling like babies, or talking like adults?
0:38:46 > 0:38:49Out come the usual suspects.
0:39:11 > 0:39:13SQUEAKING
0:39:17 > 0:39:21That's wonderful. We've got a really distinct coyote call.
0:39:21 > 0:39:25There's another one calling from across the colony.
0:39:46 > 0:39:48OK, Bill, let's do the badger.
0:40:02 > 0:40:05They're standing up where they're foraging and looking
0:40:05 > 0:40:09to see where the badger is going, and that's different from the coyote.
0:40:09 > 0:40:13For the coyote, they run to the lip of their burrow and stand there.
0:40:13 > 0:40:16For the badger, they are a little bit more reluctant to
0:40:16 > 0:40:20run to their burrow until they see which burrow the badger is going to.
0:40:22 > 0:40:23The signs are all good.
0:40:23 > 0:40:28They are at least reacting in the right way to the fake predators.
0:40:30 > 0:40:34The pups seem to be in fine voice.
0:40:34 > 0:40:38But have they learnt the proper words from the adults?
0:40:40 > 0:40:43To find out, they must compare them with pup calls
0:40:43 > 0:40:47from earlier in the year to see if they've changed.
0:40:47 > 0:40:51So let's just play the call that we got from the pups for the badger...
0:40:51 > 0:40:56- OK.- ..two months ago versus the calls that we got from them today.
0:40:56 > 0:40:58Let's see if we can hear it.
0:40:58 > 0:41:00SQUEAKING
0:41:07 > 0:41:11Yeah, again, very non-structured calls early in the season
0:41:11 > 0:41:13and highly structured calls later in the season.
0:41:13 > 0:41:17Looking at this spectrogram, you really see the difference.
0:41:17 > 0:41:19- You do.- Very detailed in the adult call.
0:41:19 > 0:41:21What we saw at the beginning of the season
0:41:21 > 0:41:25was that the pups gave very non-specific, generic calls,
0:41:25 > 0:41:29and now these same pups are giving highly structured calls.
0:41:29 > 0:41:33So, clearly, the pups have learned in just two months
0:41:33 > 0:41:37how to adapt their calls so that they sound the same as the adult calls.
0:41:37 > 0:41:39Let's see the same thing with the coyote.
0:41:39 > 0:41:41Yeah, let's do that for the coyote.
0:41:41 > 0:41:44Here we go.
0:41:44 > 0:41:46Wow.
0:41:46 > 0:41:52Again non-specific, just squeaks versus a lot of acoustic structure.
0:41:52 > 0:41:54That's really very impressive.
0:41:54 > 0:41:57- The calls are longer duration, as well.- Yeah.
0:41:57 > 0:42:01Probably because they contain a lot more information in them.
0:42:03 > 0:42:06I think this shows that learning is actually going on,
0:42:06 > 0:42:09because clearly we went from very generic,
0:42:09 > 0:42:15non-specific calls to very specific calls in just a short period of time.
0:42:15 > 0:42:19And I don't think that there's another explanation
0:42:19 > 0:42:20other than learning.
0:42:20 > 0:42:23It is possible that there is a genetic programme
0:42:23 > 0:42:26that causes the maturation of the vocal tract,
0:42:26 > 0:42:28but I think that's relatively unlikely
0:42:28 > 0:42:31compared to the possibility of learning.
0:42:32 > 0:42:39It's a eureka moment for Con and for the prairie dogs.
0:42:39 > 0:42:42They have passed all the language tests with flying colours.
0:42:44 > 0:42:48For Con, these findings are more than just about science.
0:42:48 > 0:42:52He hopes they'll make people look differently at prairie dogs
0:42:52 > 0:42:54and not see them as just vermin.
0:42:54 > 0:42:57Prairie dogs have a very complicated social system.
0:42:57 > 0:43:02They have to have some sense of their relationships between each other
0:43:02 > 0:43:05in order to maintain this social system.
0:43:05 > 0:43:07They also have this complex language,
0:43:07 > 0:43:11and they have to have some kind of intellectual structure
0:43:11 > 0:43:14in order to be able to understand this language, as well.
0:43:14 > 0:43:18So the two things combined says to us that prairie dogs
0:43:18 > 0:43:20are really very complex animals.
0:43:20 > 0:43:25After 30 years of research, Con has all the information he needs
0:43:25 > 0:43:28to help prove his bold claim that prairie dogs
0:43:28 > 0:43:33have the most sophisticated language in the animal world.
0:43:36 > 0:43:40At last the prairie dogs can step from the shadow of the bison
0:43:40 > 0:43:44and take centre stage as the true hero of the prairies.
0:43:44 > 0:43:47And they have one man to thank for that.