Date of Award


Document Type



College of Arts and Sciences

Degree Program


Degree Name

Master of Science

Thesis Advisor

William Rogers

Committee Member

Janice Chism

Committee Member

Cynthia Tant


Relatively few studies have investigated the sound production of Amazon River dolphins (Inia geoffrensis), and many questions remain regarding their social sounds. In this study, we document the presence of “low frequency narrow-band” (LFN) sounds in Amazon River dolphins. Amazon River dolphin LFN sounds were recorded in the Mamirauá Sustainable Development Reserve (Brazil), and 1,512 km away in the Área de Conservación Regional Comunal Tamshiyacu Tahuayo reserve (Peru). A quantitative comparison of LFN sounds produced by these two populations demonstrates evidence of geographic variation. The variation found in the social sounds produced by geographically separated Amazon River dolphin populations provides valuable information about this species and the plasticity of their communication signals. The differences in the analyzed LFN parameters may reflect environments, differences in group size and composition, background noise and/or evolutionary responses to geographic isolation and may impact dispersal capabilities of these animals as the first step in evolutionary divergence and speciation.