bottlenose dolphin signature whistles have just passed an important test in animal psychology. A new study by my colleagues and I has shown that these animals can use their whistles as naming concepts.
By showing urine and the sounds of distinctive whistles to dolphins, my colleagues Vincent Janik, Sam Walmsey, and I have recently shown that these whistles act as representations of the people they belong to, much like human names. For behavioral biologists like us, this is an incredibly exciting result. This is the first time that this type of representative naming has been found in any animal other than humans.
Meaning of the name
When you hear your friend’s name, you probably picture his face. Similarly, when you smell a friend’s perfume, it can also trigger an image of the friend. This is because people build mental images of each other using more than one sense. All the different information from your senses associated with a person combines to form a mental representation of that person – a name with a face, a smell, and many other sensory characteristics.
During the first few months of life, dolphins invent their own identification calls called signature whistles. Dolphins often announce their location or greet other individuals in the pack by sending out their own distinctive whistles. But the researchers didn’t know that when a dolphin hears the characteristic dolphin whistle it’s familiar with, they actively imagine the person calling. My colleagues and I were interested in determining whether dolphin calls are representative in the same way that human names evoke many human thoughts.
Dolphins use signature whistles to identify themselves.
No two branded whistles are the same.
Since dolphins cannot smell, they rely mainly on their distinctive whistles to identify each other in the ocean. Dolphins can also copy another dolphin’s whistle to address each other.
My previous research had shown that dolphins are great at remembering each other’s whistles, but scientists have argued that a dolphin can hear a whistle, know it sounds familiar, but not remember who it belongs to. My colleagues and I wanted to determine if dolphins could associate distinctive whistles with a particular owner of that whistle. This will concern whether dolphins remember and hold images of other dolphins in their minds.
Urine as an identifier
The first thing my colleagues and I had to do was find another sense that dolphins use to identify each other. In the 1980s and 1990s, researchers studying spinner dolphins in Hawaii noticed that the dolphins occasionally swam in each other’s urine and feces with their mouths open. Using these observations as a springboard, my colleagues and I set out to test whether dolphins can recognize each other in their urine.
At first, we collected the urine of dolphins under care and simply poured a small amount of it into the lagoons where the dolphins live. The dolphins immediately showed interest and after a little preparation quickly began to follow the research team every time we carried poles with cups filled with urine. When we poured urine into the water, the dolphins opened their mouths and swam through the plume of urine.
Our team then collected urine from dolphins at other facilities to see if the test subjects could distinguish between familiar and unfamiliar urine. The dolphins spent more than twice as much time with their mouths open tasting familiar urine compared to unfamiliar urine, providing the first evidence that dolphins can identify other humans by taste.
Thanks to this, my colleagues and I had what we needed to check the representativeness in signature whistles.
Conjugation of urine and whistles
Previous research on children has successfully used multiple senses to show that pre-linguistic infants can form conceptual representations of people. My colleagues and I used this type of work as the theoretical basis for our second experiment.
In our experiment, the team first led the dolphin to a speaker and then poured a small amount of urine into the water. After the dolphin tasted the urine, we quickly reproduced the sound of another dolphin’s signature whistle. Sometimes this whistle came from the same person as the urine sample. In other cases, urine and wheezing did not match. The goal was to test whether dolphins react differently if urine and whistle come from the same dolphin compared to if urine and whistle come from two different dolphins. If there was a consistent difference in how long the dolphins hovered next to the speaker in the matched and non-matched scenarios, this would mean that the dolphins knew and recognized when the whistle and the urine sample were from the same person—just as a person could make a connection. the name of a friend’s favorite perfume
We found that, on average, when urine and whistle matched, dolphins spent about 30 seconds learning about the speaker. When there was a discrepancy, they only lingered for 20 seconds.
The fact that the dolphins consistently responded more strongly to matches than to mismatches indicates that they understand which whistle corresponds to which urine. This uses the same structure as other studies that use sensory juxtaposition to demonstrate that animals have mental representations of individuals.
But what sets dolphins apart is that they don’t just fit physical traits – like a snout with a scent. They do this with the help of branded whistles that they invent themselves. Just as you can hear a name and imagine a face with all the relevant memories, dolphins can hear a signature whistle and match the signal to urine.
Dolphin language?
This work demonstrates that dolphins themselves create representative signals, just as humans have invented representative names. The representation opens up the possibility that dolphins could theoretically refer to a third dolphin when two communicating dolphins refer to a third dolphin that is not in close proximity. If dolphins could speak to dolphins that are not with them now, it would be like a mental time travel that a person makes when talking about a friend whom they have not seen for many years.
Signature whistles represent the most linguistic aspect of dolphin communication currently known. However, little is known to the scientific community about the non-signature calls of dolphins or the functions of their other acoustic signals. By further studying how dolphins communicate with sound as well as with chemicals, it may be possible to better understand the mind of these mammals.
This article was originally published on Talk on Jason Brooke of Stephen F. Austin State University. Read the original article here.