Full transcript
0:11Hello. My name is Con Slobodchikoff.
0:14I would like to tell you about the
0:16studies that my students and I have been
0:18doing in decoding the language of
0:20prairie dogs.
0:22Our studies have concentrated primarily
0:24on the language of one of the five
0:25species of prairie dogs, the Gunnison's
0:28prairie dog. However, it is very likely
0:31that the other four species of prairie
0:33dogs also have similar complexity in
0:36language.
0:38Prairie dogs have alarm calls that they
0:40give when they see a predator.
0:42These alarm calls are a series of
0:44relatively high-pitched notes that sound
0:46somewhat like a bird chirping.
0:49The alarm calls have been a Rosetta
0:50Stone for us in decoding prairie dog
0:53language because we can see the predator
0:56approach, we can record the alarm calls
0:58of the prairie dogs in response to the
1:00predators,
1:01we can video tape the escape responses
1:04of the prairie dogs, and then when there
1:06is no predator present, we can play back
1:09the alarm calls that we've previously
1:11recorded and video tape the escape
1:13responses of the prairie dogs to the
1:15playback.
1:16If the escape responses to the playback
1:19match those that happened when the
1:20predator was present, then we know that
1:23there's meaningful information encoded
1:26into the alarm call.
1:29We can bring the alarm call recordings
1:31into our laboratory and use computer
1:33analysis to look at the acoustic
1:35structure of the calls.
1:37Computer software generates a sonogram,
1:39which is a pictorial representation of
1:42the frequencies and time values
1:44contained in a vocalization.
1:46Prairie dog alarm calls look like a
1:48series of stacked chevrons, kind of like
1:51sergeant stripes with the peak pointing
1:53upward.
1:54Each call is about a tenth of a second,
1:56so it is very brief.
1:58Most of the calls are repeated multiple
2:00times so that you hear something that
2:03sounds like
2:06We can then measure the frequency and
2:08time values within a chirp and use
2:10statistical analysis to determine
2:12whether an alarm call for, say, a coyote
2:16is the same as or different than an
2:18alarm call for, say, a human.
2:21So, the analysis of the sounds is based
2:23on rigorous statistical methods.
2:27Using observations and experiments, we
2:30have found that prairie dogs give
2:31different alarm calls to different
2:33species of predators.
2:35They have one alarm call that they give
2:37for coyotes that sounds like this.
2:45They have another alarm call that they
2:48give for domestic dogs that sounds like
2:51this.
2:56They have a third alarm call that they
2:58give for humans that sounds like this.
3:05They also have a single note alarm call
3:07that they give for red-tailed hawks that
3:09sounds like this.
3:12Amazingly enough, even though some dogs
3:15look like coyotes, prairie dogs never
3:17mistake a dog for a coyote or vice
3:19versa, and always give an appropriate
3:22alarm call for each.
3:25We have also found that each alarm call
3:27contains information not only about the
3:29species of predator, but also contains
3:32information about the description of the
3:34individual predator.
3:36For example, a human alarm call contains
3:39information not only about the intruder
3:41being a human,
3:43but also contains information about the
3:45size, shape, and color of clothes that
3:48the human is wearing.
3:50When we do an experiment where the same
3:52person walks out into a prairie dog
3:54colony wearing different colored
3:56t-shirts at different times, the prairie
3:59dogs will have alarm calls that contain
4:01the same description of the person's
4:04size and shape, but will vary in their
4:07description of the color.
4:08Like many mammals, prairie dogs have
4:11dichromatic vision, which means that
4:13they can see blue, some green, and
4:15yellow, but not red.
4:19Using experiments in the field and the
4:20laboratory, we have found that prairie
4:22dogs can also describe the size, shape,
4:25and coat color of domestic dogs.
4:29Amazingly enough, prairie dogs can also
4:32describe objects that they have never
4:34seen before.
4:35In one experiment, we showed prairie
4:37dogs a silhouette of a black oval, and
4:40they all consistently had the same alarm
4:43call for the black oval.
4:45In other experiments, we have shown
4:47prairie dogs silhouettes of circles and
4:49triangles, and they consistently have
4:52different alarm calls for the circles
4:54versus the triangles.
4:57Using computer analysis, we have shown
5:00that the alarm calls are made up of
5:02smaller units of sound, very much like
5:05human phonemes such as vowels and
5:07consonants.
5:09So, each alarm call of a prairie dog is
5:12equivalent to human sentence composed of
5:14nouns and adjectives, and smaller units
5:17of sounds that make up these nouns and
5:19adjectives. The nouns are the species of
5:22predator, such as coyote or domestic
5:24dog. The adjectives are the physical
5:27descriptions of the predators, such as
5:29tall, thin, or yellow.
5:32We have also found that prairie dog
5:34alarm calls have dialects, much like
5:36human dialects.
5:38Just like a person from California might
5:40say the word dog somewhat differently
5:43from a person saying dog in Georgia,
5:46prairie dogs also have slight
5:47differences in the way that they
5:49pronounce an alarm call for say human in
5:52Arizona versus in New Mexico versus in
5:55Colorado.
5:56Prairie dogs have other vocalizations
5:58that we can't yet decode because we
6:01don't know the context.
6:03They have social chatters in which one
6:05prairie dog will lift up its head and go
6:07chatter chatter chatter
6:08and another prairie dog somewhere in the
6:10colony will respond with another string
6:12of chatter.
6:13Nothing about the behavior of the two
6:15prairie dogs changes.
6:17We can show that the syllables within
6:19the chatters are different, but because
6:21there are no behavioral changes, we lack
6:23the Rosetta Stone to decode the meaning
6:25of this.
6:27Prairie dogs also wave their tails
6:28around in a behavior known as tail
6:30flagging, but again, we don't know what
6:32the meaning of this is either.
6:35One of the best known signals of the
6:38black-tailed and Mexican prairie dogs is
6:40a jump-yell where the prairie dog stands
6:42up on its hind legs, stretches its front
6:45legs up towards the sky, and produces a
6:48yipping call.
6:50This occurs in many different contexts
6:52such as territorial disputes, a predator
6:55leaving, or a snake appearing.
6:58No one has looked at the acoustic
7:00properties of these calls to see if
7:02they're different for different
7:04contexts.
7:05Sometimes the jump-yell call occurs when
7:08there's no obvious context. Maybe in
7:11that case, the prairie dogs are simply
7:13saying, "Hooray, it's a wonderful day."
7:17I am often asked whether prairie dogs of
7:20one species can understand the language
7:22of prairie dogs of a different species.
7:25While I have not done the experiments to
7:27test this, just looking at sonograms of
7:30the different species vocalizing to the
7:32same human wearing the same color of
7:34clothes suggests that the answer is
7:36probably no.
7:38It looks like the different species have
7:40different languages just like we have
7:42French, Spanish, German, Russian, and
7:44Portuguese.
7:47At the present time, prairie dogs have
7:49the most sophisticated animal language
7:51that has been decoded, more
7:53sophisticated than even primates,
7:55whales, and dolphins.
7:57But my guess is that once we start
7:59looking at the vocalizations and signals
8:01of other animal species within specific
8:04contexts, just like we've been doing
8:06with prairie dogs, we'll find that a lot
8:08more species have complex languages.
8:12If you'd like to know more about prairie
8:14dogs, you can find out a lot more about
8:16prairie dog language in the book Prairie
8:18Dogs: Communication in Community in an
8:20Animal Society. You can find a link to
8:23this book on my website
8:24www.konstantinslobodchikov.com.