AZoLifeSciences interviews Dr. Chiara De Gregorio about searching for musical rhythms in primates and finding their answer in the Madagascan rainforest researching critically endangered lemurs.
Please introduce yourself and tell us what led you to begin this research into the evolution of rhythm.
My name is Chiara De Gregorio, a Post Doc at the University of Turin (Italy), Department of Life Sciences and Systems Biology.
Our research team started studying indris’ communication and behavior almost 15 years ago: little was known about this species, and for many years we conducted fieldwork in Madagascar to record and analyze indris’ powerful songs. In 2016 we realized for the first time that indeed these primates have rhythm, and this bought us to compare their rhythm to human music’s ones.
Why do you think it is important to understand music and rhythm in primates?
Music and rhythm are two very important aspects in our daily life. Still, the reason why we enjoy so much music and dancing is highly debated. Studying animals' rhythmic and musical abilities can help us to understand why music is such a preponderant aspect of our own behavior.
Image Credit: PopTika/Shutterstock.com
What is a categorical rhythm and how does this relate to humans?
Rather than defining music itself, categorical rhythms may inform about the temporal organization of an acoustic signal. For example, if we think about a clock that is ticking we can say that it makes an isochronous sound since intervals have the same duration, but we would not think of it as “music”.
Besides, if we move into the musical domain and we think about all the possible intervals between notes in a melody, the presence of categorical rhythms indicates that the note timing is not random, but follows a precise temporal organization. This is a very important musical feature, as thanks to categorical rhythms, any song sung at different tempi will still be recognizable. Categorical rhythms have been found across human music in different cultures, so they are a musical universal.
What did you find regarding Indri indri lemur songs?
In human music, rhythm plays a very important role, and intervals between the beginning of a note and that of the following one usually have a simple relationship. For example, two subsequent intervals may have the same duration, or maybe the second is twice the first one. These two cases correspond to two rhythmic categories, and we can find them, for example, in the intro of “We will rock you”, the famous song by Queen.
Guess what? Those are exactly the same two rhythmic categories we discovered in the indris’ songs. This is the first evidence of the presence of a typical trait of human music in another mammal.
What do your findings tell us about the evolution of Indri indri in relation to humans?
Finding in indris musical universals may indicate that human music is not truly novel but its intrinsic musical properties are more deeply rooted in the Primate lineage than previously thought.
Image Credit: Filippo Carugati
How did you carry out this research on lemur individuals from the Madagascan rainforest?
The data collection was probably the most challenging part of our research. Indris live all their life up in the canopy of Madagascar’s rainforest, jumping from tree to tree, up and down the hills. So, for many years, we have followed them in the humid forest, in every weather condition, for 8-9 hours a day, recording with microphones their powerful songs. Moreover, some days indris may not sing at all, so this is why it required all this time to collect a proper dataset for this work.
The Indri indri is a critically endangered species. Could your research be used to help to raise awareness for this species and its conservation?
We really hope that our exciting findings can also bring attention to indris’ critical situation. It is really sad to think how endangered these special primates are: at the moment, every attempt to build captive populations has failed and their habitat is vanishing quickly.
Once the forest is gone, they are gone too. They still have so much to teach us, and our research group is working very hard also for their conservation. I think that building a connection between us and them could be a key factor in sensitizing the public and taking conservation action.
What is the significance of finding this phenomenon in an endangered species, and how can we learn from this?
Most singing primates, as indris, are critically endangered or endangered. Given the songs’ peculiar features and commonalities with human language, we would argue that singing species would represent an excellent model for studies on the evolution of human communication.
Still, the knowledge of some singing primates such as titi monkeys and tarsiers is scanty. I think our work might stress the importance of focusing on these endangered animals before it’s too late.
Cute Jumping Indri Lemurs | Madagascar | BBC Earth
What is the next step for this study?
I think our next step will be to investigate if these categories are already in place and fixed at birth in indris, or if animals somehow need to develop and practice them. This will be interesting to understand if these rhythmic features might be involved in signal acquisition and, possibly, learning.
Where can readers find more information?
About Dr. Chiara De Gregorio
Chiara De Gregorio is a PostDoc at the University of Turin. After an MSc in Evolution of Human and Animal Behaviour, she pursued a Ph.D. focused on indris’ rhythmic abilities.
She has conducted fieldwork in Madagascar and Ethiopia. Her main interests are primates’ communication and conservation.