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February 20, 2012
Covert Communications Channel in Tarsiers
Marissa A. Ramsier, Andrew J. Cunningham, Gillian L. Moritz, James J. Finneran, Cathy V. Williams, Perry S. Ong, Sharon L. Gursky-Doyen, and Nathaniel J. Dominy (2012), "Primate communication in the pure ultrasound," Biology Letters.
Abstract: Few mammals -- cetaceans, domestic cats and select bats and rodents -- can send and receive vocal signals contained within the ultrasonic domain, or pure ultrasound (greater than 20 kHz). Here, we use the auditory brainstem response (ABR) method to demonstrate that a species of nocturnal primate, the Philippine tarsier (Tarsius syrichta), has a high-frequency limit of auditory sensitivity of ca 91 kHz. We also recorded a vocalization with a dominant frequency of 70 kHz. Such values are among the highest recorded for any terrestrial mammal, and a relatively extreme example of ultrasonic communication. For Philippine tarsiers, ultrasonic vocalizations might represent a private channel of communication that subverts detection by predators, prey and competitors, enhances energetic efficiency, or improves detection against low-frequency background noise.
Posted on February 20, 2012 at 6:30 AM
• 6 Comments
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"Why not? It worked for Zarathustran Fuzzies."
Tarsiers also see in the dark, quite well, and unlike most mammals with good low-light vision, their low-light vision is trichromatic. (They have freakishly huge eyes; try googling "tarsier skull".)
And many species are endangered, though I think the status of the Phillipine Tarsier was recently changed from endangered to "data deficient".
But they are closely related to other earth primates (as seen in both their genetics and their morphology), so they couldn't have arrived in space ships ...
"enhances energetic efficiency, or improves detection against low-frequency background noise" both seem unlikely. Ultrasonics have severe excess attenuation in dense jungle, and the effect increases rapidly with frequency. At this very high frequency we would expect somewhere around 1.5 dB/m excess attenuation.
It would be interesting to compare to the acoustic sensitivity of their main predators to check the "covert communication" hypothesis.
However, two other hypotheses cometo mind as well. First, this is a leaping animal, and it is insectivorous. Is it possible that it echo-locates?
Secondly, very small animals tend to be more sensitive to ultrasonics simply due to wavelength effects. And this is an extremely small primate.
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