The acoustic environment of the Florida manatee: Correlation with level of habitat use

The Florida manatee is regularly exposed to high volumes of vessel traffic and other human‐related noise pollutants because of their coastal distribution. Quantifying specific aspects of the manatees’ acoustic environment will allow for a better understanding of how these animals are responding to both natural and human induced changes in their environment. Acoustic recordings and transmission loss measurements were made in two critical manatee habitats: seagrass beds and dredged basins. Twenty‐four sampling sites were chosen based on the frequency of manatee presence in specific areas from 2000–2003. Recordings were composed of both ambient noise levels and transient noise sources. The Monterey‐Miami Parabolic Equation Model (MMPE) was used to relate environmental parameters to transmission loss, and model outputs were verified by field tests at all sites. Preliminary results indicate that high‐use grassbeds have higher levels of transmission loss compared to low‐use sites. Additionally, high‐use grassbeds have lower ambient noise in the early morning and later afternoon hours compared to low‐use grassbeds. The application of noise measurements and model results can now be used to predict received levels, signal‐to‐noise ratios, and reliable detection of biologically relevant signals in manatee habitats and in the many different environments that marine mammals live.