0:03 This is Dr. Con Slobodchikoff.
0:04 For over 30 years he has studied
0:06 communication in prairie dogs and his
0:08 work represents some of the most
0:10 sophisticated research we have to date
0:12 about animal communication.
0:14 His findings show that prairie dogs can
0:16 not only use words to identify specific
0:18 species of predators, but are even able
0:20 to provide detailed descriptions of
0:23 individual predators such as their color
0:24 and size.
0:25 This may not sound like much at first,
0:27 but for a long time scientists believed
0:29 that animal calls are simply emotional
0:32 reactions to the world around them.
0:33 The ability to have specific or
0:35 meaningful communication has often been
0:38 considered to be uniquely human.
0:40 Yet through decades of experiments he
0:41 has found that prairie dogs are able to
0:44 use adjectives and even create new words
0:46 for things they had never seen before.
0:48 Now, this certainly sounds very
0:49 exciting, but at this point you're
0:51 probably wondering how does he actually
0:52 prove this?
0:54 Well, let's take a step back and look at
1:04 >> At a young age Con learned a very
1:05 important lesson that would come to
1:07 shape his entire career.
1:09 Having grown up speaking Russian, when
1:11 he first moved to the United States his
1:12 teachers didn't realize that some
1:14 children simply didn't grow up speaking English.
1:15 English.
1:17 Instead they assumed something was wrong
1:19 when he spoke slowly and sent him to a
1:20 psychologist where he was quickly
1:24 diagnosed with a speech disability.
1:25 This experience taught him something
1:28 important very early in life that even
1:30 experts can be wrong when they rely too
1:32 heavily on their assumptions.
1:34 Years later that lesson would quietly
1:36 shape the way he came to look at animals.
1:37 animals.
1:39 Because outside of school Con found he
1:40 developed a love for the animals around him.
1:41 him. >> [clears throat]
1:41 >> [clears throat]
1:43 >> As a teenager he joined an academy where
1:45 he went on numerous field trips to
1:48 different habitats across California.
1:49 For the first time he was able to spend
1:51 hours watching animals in the wild to
1:53 observe their behavior and their interactions.
1:54 interactions.
1:56 And this fascinated him because all his
1:58 life he had been told that animals were
2:00 simple creatures and weren't capable of
2:02 complex thoughts.
2:04 Yet what he saw in the field was vastly different.
2:06 different.
2:07 And as he reflected on his own
2:09 experience in school, he wondered if we
2:11 might be making a similar mistake when
2:14 we think about animals.
2:16 So after receiving his PhD, Con set out
2:18 to study the social behavior of prairie dogs.
2:19 dogs.
2:21 But little did he know this would soon
2:24 lead him down a very different path.
2:26 So next, let's take a look together at
2:35 >> When he first started his research, Con
2:37 had often noticed that prairie dogs gave
2:39 alarm calls whenever predators were nearby.
2:40 nearby.
2:42 At the time, like most researchers, he
2:43 assumed that these calls were fairly
2:45 simple and was just a general signal
2:48 that something dangerous was close.
2:50 But one day he came across a paper which
2:51 found that ground squirrels in
2:53 California used different alarm calls
2:56 for aerial and ground predators.
2:58 He thought this was pretty interesting
2:59 and wondered if it could apply to
3:01 prairie dogs as well.
3:03 So the next time he was in the fields,
3:05 he started paying closer attention.
3:07 And sure enough, whenever a hawk
3:09 appeared, the prairie dogs made this sound.
3:16 A short single note bark. But when there
3:18 were dogs, coyotes and other ground
3:20 predators nearby, they instead made this
3:28 Which was a slightly different sound,
3:30 but repeated rapidly.
3:31 Now he thought this was really interesting.
3:32 interesting.
3:34 Over the next few weeks Con found
3:36 himself spending longer and longer in
3:38 the field taking notes on everything
3:39 that he saw.
3:41 And as his ears became more and more
3:42 tuned to the sounds they made, he
3:44 started to notice something very strange.
3:45 strange.
3:47 It seemed like the sound they made for
3:49 different ground predators had very
3:51 slight variations to them.
3:52 But more than that, it seemed to always
3:55 vary in the exact same way depending on
3:57 the type of predator.
3:59 And slowly an idea began to take shape
4:02 in his mind. So then I had an insight.
4:05 What if the prairie dogs are
4:08 talking about the species of predator?
4:09 Now mind you,
4:12 nobody believed this
4:14 at the time.
4:16 But I thought, what if? >> [snorts]
4:16 >> [snorts]
4:19 >> So he decided to try and test this. He
4:21 would first observe how they would react
4:22 when there were different predators nearby.
4:23 nearby.
4:25 He noticed that when coyotes were
4:26 nearby, the prairie dogs would make this sound.
4:34 And they would also run to their burrows
4:36 and stand alert.
4:38 For domestic dogs, they instead made
4:44 But rather than run to their burrows,
4:46 they would simply stand alert wherever
4:48 they were at the time. And it's
4:50 important to note that they would never
4:52 make a mistake even when certain
4:54 domestic dogs looked very similar to coyotes.
4:56 coyotes.
4:58 And finally, for humans, they made this sound.
5:04 And they would respond by not only
5:05 running to their burrows, but would
5:07 quickly dive inside.
5:09 He believed the different responses was
5:10 likely due to how dangerous they
5:13 perceived each predator to be.
5:14 Next, he would record the calls made
5:16 against each predator and replay the
5:18 recorded sounds to different colonies of
5:20 prairie dogs.
5:21 If they really were communicating
5:23 something beyond just ground predator,
5:25 then they should react appropriately to
5:27 each call.
5:29 And when he did, that's exactly what happened.
6:00 Over hundreds of trials, the prairie
6:03 dogs always responded in the appropriate way.
6:04 way.
6:06 And with this he had shown that prairie
6:08 dogs weren't just making simple alarm
6:09 calls, but there was specific
6:12 information being transmitted in these calls.
6:13 calls.
6:14 When I started working with prairie
6:18 dogs, I started exploring this issue and
6:20 eventually found
6:22 that in the alarm calls of prairie dogs,
6:25 they have different alarm calls for
6:27 different species. They have an alarm
6:29 call for a human, they have an alarm
6:32 call for a coyote, another one for a
6:35 dog, another one for a hawk. We found
6:37 some other alarm calls for other animals
6:39 as well.
6:41 But this begs the question, how do we
6:43 know that they are actually referring to
6:45 the species rather than just telling
6:47 each other to run or hide in a certain way?
6:48 way?
6:50 To answer that, we'll look at a very
6:52 interesting piece of evidence in the
7:01 >> As Con continued his research, he began
7:03 building a much larger library of alarm
7:04 calls from different predator
7:06 encounters. But one thing kept bothering him.
7:07 him.
7:09 To human ears, many of these calls
7:11 sounded incredibly similar, yet the
7:13 prairie dogs never seemed confused and
7:15 always seemed to know exactly what kind
7:17 of predator was nearby.
7:20 So he began looking more closely at the
7:22 calls themselves using spectrograms to
7:24 compare their structure and sorted them
7:26 by predator type.
7:27 And then he noticed something very interesting.
7:29 interesting.
7:30 While calls for the same predator seemed
7:32 to follow a certain pattern in their
7:34 frequency and structure, there was still
7:36 a lot of variation between the
7:38 individual calls themselves. Much more
7:40 than you'd expect based on natural
7:43 differences in individual prairie dogs.
7:45 But that raised the bigger question. If
7:47 the overall pattern already told them
7:48 the predator category, then why was
7:50 there still so much variation between
7:52 the individual calls?
7:54 And one day as he was staring out into
7:56 the prairie, a thought began to surface
7:58 in his mind.
8:00 So again I had an insight. What if they
8:04 are describing the individual features
8:05 of predators?
8:08 Now this is really way out
8:09 at the time.
8:12 Nobody, but nobody believed that.
8:14 Nobody, but nobody hardly believes that
8:16 at all today.
8:18 So he designed an experiment to try and
8:20 test this.
8:21 He first had one of his students walk
8:22 through the prairie field on one of
8:25 three randomized paths wearing a blue
8:27 shirt and recorded the calls they made.
8:29 And then they repeated this with a green
8:31 and yellow shirt.
8:33 He would repeat this many times before
8:35 analyzing each of the calls.
8:37 And what he noticed was that while all
8:38 the calls were consistent with the
8:40 pattern of human calls, they were
8:42 different each time.
8:44 But it wasn't that simple because while
8:45 the blue shirt calls were distinctly
8:47 different to the others, this wasn't the
8:49 case between the yellow and green shirt
8:52 calls, which were much more similar.
8:53 Now this is really interesting because
8:55 prairie dogs have dichromatic color
8:57 vision, meaning while they can easily
8:58 distinguish between blue and yellow
9:00 wavelengths, they have a much harder
9:03 time doing so for green and yellow,
9:05 which are much closer to one another.
9:07 This suggests that prairie dogs are in
9:09 fact actively changing what they're
9:10 saying based on the individual
9:13 appearance of specific predators.
9:15 The other really interesting thing he
9:16 noticed was that the prairie dogs still
9:18 responded the same way to the different
9:21 colored calls by running to the burrows
9:23 and diving inside.
9:24 And Con believed that this provided more
9:26 evidence that they weren't just telling
9:28 each other how to run and hide, but
9:30 rather actively encoding information on
9:33 the predators themselves.
9:34 He would later do this for different
9:36 factors like size, speed of approach and
9:39 shape. And in one experiment, he even
9:41 tested whether prairie dogs would have a
9:43 distinct reaction to someone holding a gun.
9:44 gun.
9:48 We had a person walk out in a blue shirt
9:51 who was carrying a shotgun and initially
9:54 he fired the shotgun off into the air.
9:55 And [music]
9:58 the prairie dogs gave an alarm call for
10:01 him that indicated that he had a blue
10:03 shirt and described his physical
10:05 features, but they also had an addendum,
10:08 [music] which we thought indicated that
10:11 he had a gun. And then for the length of
10:13 the experiment, another month, whenever
10:15 he showed up,
10:15 he was >> [music]
10:15 >> [music]
10:17 >> always dressed the same way, so they
10:20 gave the call for him describing that he
10:22 had a blue shirt, but they also tacked
10:25 on this addendum, which we thought
10:27 carried the meaning of a gun. So for a
10:29 month, they remembered
10:32 From his observations, Cohn suspects the
10:33 reason why they need to encode so much
10:35 information into their calls is because
10:37 it allows them to respond appropriately
10:39 to individual predators, particularly
10:41 ones that they know that have been very
10:43 dangerous in the past.
10:45 For example, if a coyote has a
10:46 particular hunting style, like lying
10:48 next to a burrow and waiting for prairie
10:50 dogs to come out, thinking they're safe,
10:52 then knowing when that coyote is around
10:55 can help them survive this.
10:57 Now, this is pretty amazing, right? And
10:59 when Cohn first realized this, he was
11:01 extremely excited. And he couldn't help
11:02 but wonder what words the prairie dogs
11:05 used to describe him.
11:06 But despite this, there was one question
11:08 left in Cohn's mind.
11:10 All his life he had been told that
11:12 animals lack the capacity to create
11:15 meaning or have novel thoughts. So how
11:16 would they respond if they came across
11:25 In the months that followed, this
11:28 question kept coming up in Cohn's mind.
11:29 And the more he spoke to colleagues
11:32 about it, the more impossible it seemed.
11:34 Different calls and descriptions for
11:36 predators was one thing, but being able
11:38 to come up with new words is a different
11:40 claim entirely.
11:42 And yet, if their language really was as
11:44 complex as Cohn thought it to be, then
11:46 at some point, they would eventually
11:48 come across things they hadn't seen previously.
11:49 previously.
11:51 And so, in spite of all the pushback
11:53 from his colleagues, he decided to push on.
11:54 on.
11:56 For this experiment, he needed prairie
11:58 dogs something they had never seen
12:02 before, something alien in nature.
12:05 And for that, he chose a triangle.
12:07 Or more specifically, the silhouette of
12:09 a triangle, because there was no way the
12:11 prairie dogs would have ever seen a
12:14 triangle approaching them in nature.
12:15 So what he did was he first built
12:18 observation towers within the colony and
12:19 set up a pulley system between the towers.
12:21 towers.
12:22 He would then attach wires to a large
12:25 cardboard cutout of a triangle.
12:26 Then they would essentially have the
12:28 triangle run across the field while
12:30 observing how the prairie dogs responded.
12:31 responded.
12:33 They also later did this with cutouts of
12:35 an oval and a rectangle.
12:37 And it's quite interesting to think
12:38 about what the prairie dogs were
12:40 thinking in those moments.
12:42 But what they found was that the prairie
12:44 dogs would make a call that was unlike
12:46 anything they had heard before.
12:48 It was distinct in its overall acoustic
12:50 structure, yet surprisingly consistent
12:52 amongst all prairie dogs that saw the
12:54 moving shape.
12:56 This suggests that these calls were not
12:58 just made from confusion or surprise
13:00 from one single individual.
13:02 Instead, it seems their communication is
13:04 flexible enough to extend to something
13:06 entirely new.
13:10 We had circles and we had triangles
13:13 running across the field on a set of
13:16 wires, and the prairie dogs had distinct
13:18 calls for the circles and they had
13:20 distinct calls [music] for the
13:23 triangles. So these are things that
13:25 prairie dogs have never seen before, and
13:27 yet they were able to come up with a
13:28 novel word >> [music]
13:28 >> [music]
13:30 >> for each one of those things, for an
13:39 >> Cohn has often wondered why we are so
13:41 quick to assume that language is
13:42 something only humans [music] are
13:44 capable of.
13:46 After all, if we already accept that we
13:48 share so much with other animals, like
13:50 our biology, our DNA, even our immune
13:51 systems, then [music] why not
13:54 communication, too? Especially when such
13:55 a thing would offer such a clear
13:57 survival advantage.
13:59 There's no doubt that our language is
14:01 likely more complex than most others out
14:03 there, but to Cohn, language is less
14:06 something animals either have or don't,
14:08 and more something that may instead
14:10 exist on a spectrum.
14:12 And what I found especially moving was
14:14 that even after all these years, he
14:16 never seemed interested in proving that
14:18 point through cruelty.
14:20 Some critics argue that to really test
14:22 these ideas, prairie dogs [music] should
14:24 be raised in captivity, isolated, or
14:27 subjected to more invasive experiments.
14:28 But Cohn never agreed with that
14:31 approach, because for him, [music] these
14:33 were never just experimental subjects.
14:36 They were living animals.
14:38 Even late in his career, what stood out
14:39 to me was how much his work was driven
14:41 not just by scientific [music]
14:44 curiosity, but by genuine care.
14:45 He spoke about the countless animals
14:47 that are put down each year for
14:49 so-called bad behavior, and wondered how
14:51 much of that suffering might come from
14:53 [music] a much simpler problem.
14:55 That we still simply don't understand
14:57 what they're trying to say.
14:59 He hopes for a future where our research
15:01 will one day allow us to build tools
15:02 [music] that could help us translate
15:05 animal signals in real time, and really
15:06 narrow the gap between [music] their
15:09 world and ours.
15:11 Even after retiring from academia, Cohn
15:13 never really stopped his work.
15:15 He spent years continuing to speak
15:16 publicly [music] about animal
15:18 communication through books and
15:20 interviews to try and convince the world
15:21 that animals may be saying far more
15:23 [music] than we give them credit for.
15:25 He even wrote a book called Chasing
15:27 Doctor Doolittle, in which he details
15:29 his life's work and the [music] long
15:30 struggle to get others to take animal
15:33 communication seriously.
15:34 Because if there was one thing that Cohn
15:36 has found after all these years, the
15:38 real challenge was perhaps never about
15:41 getting animals to speak, but rather
