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Last year, a team composed of scientists from the USA and the Philippines observed calls of the Philippine tarsier that is purely within the ultrasonic domain [1]. They said that these “are among the highest recorded for any terrestrial mammal, and a relatively extreme example of ultrasonic communication.”

Listen to the Philippine tarsier’s ultrasonic voice with 8 times slower frequency here [1] (but I have to warn you that you may find it irritating):[audio http://now.dartmouth.edu/wp-content/uploads/2012/02/tarsier.mp3]

This year one of the researchers in [1] observed ultrasonic calls that differ in frequencies. 

The chirp which is as short as a fraction of one thousandth of a second has an average audio frequency of 22 kHz.  The twitter has a duration of about 120 millisecond at an average audio frequency of 38 kHz. The whistle has the longest duration at an average audio frequency of 76 kHz [2]. For comparison, the audible frequency of an average human is between 0 to 20 kHz.

Tarsier’s ultrasonic calls as written in [2], compared to the average audible range of a human, a dog and a bat. Click to enlarge.

The researcher said that these ultrasonic calls most likely serve as distress calls. However, the whistle according to the author may have a specific purpose as it can only be ‘heard’ on certain circumstances during the study.


[1] Ramsier MA, Cunningham AJ, Moritz GL, Finneran JJ, Williams CV, Ong PS, Gursky-Doyen SL, & Dominy NJ (2012). Primate communication in the pure ultrasound. Biology letters, 8 (4), 508-11 PMID: 2319094http://now.dartmouth.edu/2012/02/tiny-primate-is-ultrasonic-communicator-dartmouth-professor-finds/

[2] Gursky-Doyen S (2013). Acoustic characterization of ultrasonic vocalizations by a nocturnal primate Tarsius syrichta. Primates; journal of primatology, 54 (3), 293-9 PMID: 23549838

[3] Tarsier and shadow images are from wiki commons.