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Thesis - NSU Access Only
M.S. Marine Biology
Edward O. Keith
Photo-identification and telemetry studies have reported limited instances in which Florida manatees (Trichechus manatus latirostris) traversed the coastline of Florida. Manatee calls were recorded from four different locations in Florida. Using a single hydrophone, calls were recorded at two sites on the east coast and two sites on the west coast of Florida. These locations were representative of the four manatee management zones adopted by the Florida Fish and Wildlife Conservation Commission and the United States Geological Service. These include the Northwest, Southwest, Atlantic and Upper St. John’s River regions. Seven hundred calls from each site were selected for analysis to further quantify call parameters and evaluate differences within and across geographical locations. Fundamental and dominant frequencies, call duration, number of harmonics, and the percentage of frequency modulation, were measured, in addition to the first and third quartile frequency, energy, interquartile bandwidths. Spectrograms and statistical differences in frequency modulated vocalizations (one-way anova, p <0.0001) were used to classify calls into six categories; whistles, squeaks, high squeaks, squeak-squeals, chirps and squeals. (1) Whistles are narrow tonal calls with no frequency modulation. The frequency range for these calls is 1800 – 5000 Hz and a duration of 0.080 – 0.382 s. (2) Squeaks are more complex frequency modulated calls with 2 - 4 harmonics even at low intensities. They have a duration of 0.052 – 0.681 s and a frequency range of 562.1 – 10,312.5 Hz. (3) Squeals have no frequency modulation, are wideband signals, have a duration of 0.077 – 0.562 s and a frequency range of 468.4 – 6656.8 Hz. (4) Squeak-squeals have characteristics of squeaks and squeals. They may or may not have frequency modulation, have a duration of 0.090 – 0.612 s and a frequency range of 750.1 – 8625.5 Hz. High squeaks are strongly modulated, have a duration of 0.131 – 0.236 s, and a frequency range of 1,300.2 – 10,628.8 Hz. Chirps are characterized by having two or three dominant energy bands that are separated by short gaps, have frequency modulation, a duration of 0.031 – 0.283 s, and a frequency range of 1,265.3 – 6937.5 Hz. Since it was unknown which manatee was eliciting the call, group means of the variables center fundamental frequency and first and third quartile frequency where used to analyze differences or similarities within and between coastlines. A T test was used to compare means at a 95% confidence interval. Spectrograms of the categorized calls were analyzed within and between coastlines. Results from t-tests suggest there are no differences in calls for the variables studied within and between east and west coast populations of the Florida manatee (all p values > 0.05). Correlation of spectrographic images suggests there is a high degree of similarity among categorized calls and calls seem to differ mostly in call contour.
Beth A. Brady. 2011. Intraspecific Comparison of Vocalizations of the Florida Manatee (Trichechus manatus latirostris) on the East and West Coast of Florida. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, Oceanographic Center. (208)