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Degradation characteristics of golden lion tamarin (Leontopithecus rosalia) two-phrase long calls: implications for call detection and ranging in the evergreen forest.

Vera Sabatini, Carlos R. Ruiz-Miranda and Torben Dabelsteen (2011). Degradation characteristics of golden lion tamarin (Leontopithecus rosalia) two-phrase long calls: implications for call detection and ranging in the evergreen forest.. Bioacoustics, Volume 20 (2): 137 -158

 

Abstract: 

Neotropical primates have evolved long calls, which have a role in spacing and cohesion of groups. Detection and “reading” of long calls as well as ranging of calling individuals seem essential for this role. This study used sound propagation experiments to investigate habitat caused degradation of long calls of the Golden Lion Tamarin Leontopithecus rosalia and its implications for “reading” and ranging long calls of calling tamarins. The experiments were made in lowland, evergreen forest in Brazil. Synthesized copies of natural sounds were broadcast and re-recorded using different combinations of microphone and speaker heights of 2.0 and 7.5 m and distances of 2.5, 10, 20, 40 and 80 m. Excess attenuation, blurring, signal-to-noise ratio and energy of tail of echoes were quantified. The highest frequency sounds attenuated most at all distances, showing the lowest signal-to-noise ratio. The more effective sound propagation at 2.0 m (below the canopy and in the upper part of the dense undergrowth where they forage) facilitates reading of the information content of the long calls and hence their use for communication during foraging. Although the high degradation of the long calls with distance at microphone and speaker heights of 7.5 m (inside the canopy) constrains reading of the long calls’ information content it does provide very good conditions for ranging and may be one of several reasons for why long-calling tamarins approach long-calling neighbours through dense vegetation for group encountering.

Keywords: 
golden lion tamarin; long call; sound degradation; communication; ranging cues