Abstract
I examined the acoustic ecology of coastal bottlenose dolphins (Tursiops truncatus) in the Big Bend region of Florida and compared it to other populations of dolphins found in similar habitats. This region is one of the most acoustically pristine coastal environments in Florida, marked by little human activity. Historically this region’s dolphin population has not been studied, leaving a gap in our knowledge of these animals. Acoustic recordings were collected as part of photo-identification and habitat-use surveys, and then categorized into fall, winter, spring, and summer seasons. Whistle rates were highest in spring, even when normalized for group size. Echolocation rates were not different between seasons over both years, but individual years had differences. Interestingly, burst pulse sounds and pops rarely occurred.
Bottlenose dolphins are not the only source of noise in their marine habitat, so to understand the acoustic environment of these animals, human- and fish-produced sounds were also considered. Remote autonomous acoustic recorders were deployed at eight sites in the Big Bend region and each location was found to have a unique soundscape with respect to dolphin, fish, snapping shrimp, and human-produced sound. Toadfish (Opsanus beta), sea catfish (Arius felis), and silver perch (Bairdiella chrysoura) were the only identifiable fish species to produce sound and caused notable increases in sound levels at low frequencies where they vocalized. There were twelve unidentifiable biological sounds; all exhibit properties of fish or invertebrate produced sounds. Locations exhibited different temporal peaks in fish sound production. Overall, human-produced noise was uncommon and only found in the form of boat noise, but when present it greatly increased sound levels, especially in low frequencies. Dolphin vocalizations were not found at all locations, however, the lack of dolphin vocalizations does not necessarily mean that dolphins were not present in these regions. This study confirmed that the region is relatively acoustically pristine.
|
