Classification of Florida manatee (Trichechus manatus latirostris) vocalizations.

Abstract

The vocal repertoire for the Florida manatee is quantitatively categorized from a sample of 1114 calls recorded from 3 different manatee habitats in Florida. First, manatee vocalizations were categorized into five call categories based on visual inspection of spectrograms and following descriptions provided in previous studies. Second, based on measurements of 17 acoustic parameters, the subjective classification scheme was validated using classification and regression trees (CARTs) and model-based cluster analysis paired with silhouette coefficients. CART analysis revealed that these five broad call categories can be successfully distinguished based on correct classification scores of 41.6%-62.5%. Silhouette coefficients determined that the manatee vocal repertoire is highly intergraded. This study supports and expands upon existing subjective categorization schemes by providing a quantifiable methodology for describing the Florida manatees' vocal repertoire. These findings contribute to the increasing number of studies suggesting many animal species vocal repertoires contain graded call types.