Tiny, ape-like creatures called tarsiere sing operatic-style duets together — but those who fail to hit the high notes may also fail to attract mates, scientists have recently suggested.
With their large, pointed ears and expressive eyes, nocturnal tarsiers bear a striking resemblance to the little Jedi Master Yoda from the Star Wars films. But while Yoda has never demonstrated operatic skills, tarsiers are energetic singers who use vocals as a form of sexual selection, or signaling one another that it’s time for all members of a troupe to gather for sleep, according to a new study.
To learn more about these song performances, scientists overheard tarsiers in July and August 2018 in Tangkoko National Park in Sulawesi, Indonesia, and captured 50 recordings of 14 pairs of Gursky’s spectral tarsiers (Tarsius spectrum gurskyae) sing their morning duets. Researchers at Sam Ratulangi University in Sulawesi and Cornell University in Ithaca, New York used machine learning to distinguish and classify notes and musical phrases in the tarsiere’s songs. Their findings were published in the journal on August 2nd Frontiers in ecology and evolution (opens in new tab)suggest that these performances are so strenuous that not all tarsiers can master the fast, high notes, and duet.
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Gursky’s spectral tarsiers are only 9 to 15 centimeters long and weigh no more than 200 grams. They live only on Sulawesi, an Indonesian island east of Borneo. Described as a separate species from other tarsiers in 2017, they were classified as Vulnerable by the International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species. About 13 species of tarsiers inhabit islands in Southeast Asia.
The researchers recorded the tarsiers’ duets using a portable digital recorder and autonomous recording devices installed in the tarsiers’ jungle habitats. “At least in Tangkoko National Park, tarsiers are among the easier primates to capture and study because they have small home ranges and appear to be dueting most mornings,” said lead study author Dena Clink, a researcher at Cornell’s K. Lisa Yang Center for conservation bioacoustics. “They aren’t afraid of humans, so it was relatively easy for us to get quality footage.”
When the scientists analyzed the intricate duets performed between male and female tarsiers, they found that the performances resembled coloratura — a singing style that produces many notes very quickly and is used by opera singers during arias to increase their control and demonstrate virtuosity.
“The duets exhibit acoustic compromises in note rate and note bandwidth — the range of frequencies within a note,” said Isabel Comella, lead author of the study and researcher at the K. Lisa Yang Center. The slower-singing tarsiers do so with the widest range of frequencies within a note, while the tarsiers that repeat notes faster only seem able to master a narrower range of frequencies within a note, Comella told Live Science in an email. Only a minority can do both at the same time. The authors hypothesize that singing notes rapidly over a wide range of frequencies during a duet may be more physiologically and neurologically taxing for the singer, since only physically fit individuals are capable of it.
Why tarsiers duet in such complex and physically demanding ways is unknown, largely because the animals are rarely studied. Other primates have been known to sing duets, including one species of lemur called Indri (Indri Indri), Titus monkeys in which Callebus Genus and northern gray gibbons (Hylobates funereus), according to the authors. Previous studies of primate duets suggest that this behavior may be used for finding or guarding a mate, defending territory, or strengthening social bonds, although more research is needed to determine exactly why tarsiers perform these duets, reported the study authors.
However, one possibility for the Sulawesi tarsiers is that their duet could be connected to the organization of their social groups. Tarsiers often forage for insects alone at night and then reunite in the morning to sleep, and they can sing together at night “to get all group members to the same roost tree,” a feature not seen in other duets, primates said Comella.
According to the authors, it could be a unique behavior of tarsiers in Sulawesi. Tarsiers in the Philippines and Borneo are solitary animals and do not form duets as regularly.
Although Gursky’s spectral tarsiers sing their duets in the range of human hearing, the primates also speak in the ultrasonic range, which researchers are currently studying. “We hope that with the advent of inexpensive autonomous recording devices and even smartphones, we can begin to learn more about the vocal behavior of tarsiers on Sulawesi,” Clink said.
Originally published on Live Science.