The Philippine Tarsier, living in the South Eastern part of the archipelago, is one of the tiniest primates in the world. It’s a nocturnal animal, with big, fixed eyes. It was also described as a quiet species, until US researchers have revealed that it is not that they don’t emit sounds, but that they “talk” within the pure ultrasound domain, this is, above 20 kilohertz.
Usually humans are able to hear sounds below this frequency, and just few mammals, like cetaceans, cats and some bats and rodents, express sounds above it. After recording wild tarsiers with an ultrasound detector, the researchers found that they could hear up to 91 kHz and send sounds of at least 70 kHz.
“This is the first time that a primate has been shown to use vocalization that is only in the ultrasound, so this call doesn’t use anything in the lower frequencies that we can hear,” said Marissa A. Ramsier, researcher at the Department of Anthropology at Humboldt State University, USA, and co-author of the study.
The idea for the study came out when scientists saw that tarsiers used to open their mouth as to emit some sound. They first recorded some wild tarsiers in their habitat, and then, in order to deepen the study, they captured six specimens, which were subjected to more precise techniques of capturing the sound and measuring the frequency.
The research, published today in Biology Letters, suggests that other primates might communicate in ultrasound. This skill may be useful against possible threats and to capture prey without being noticed.
Photo: Sakurai Midori
Ramsier, M., Cunningham, A., Moritz, G., Finneran, J., Williams, C., Ong, P., Gursky-Doyen, S., & Dominy, N. (2012). Primate communication in the pure ultrasound Biology Letters DOI: 10.1098/rsbl.2011.1149