Historical Evidence of Tursiops truncatus Exhibiting Habitat Preference and Seasonal Fidelity in Northeast Florida.

Degradation of coastal and estuarine habitats is probably inevitable when more people move to coastal regions. To determine potential effects of habitat degradation on a species, the extent of exposure due to habitat fidelity and any characteristics that make the habitat preferable need to be identified. Common bottlenose dolphin (Tursiops truncatus) density and distribution in northeastern Florida were seasonally heterogeneous in 1994 through 1997. Regional and seasonal fidelity patterns and habitat variable preferences (e.g., salt marsh, residential density, etc.) of individual dolphins were examined to determine if this heterogeneity was due to significant preferences. Thirty-six bottlenose dolphins were sighted more than expected (preferred) in estuarine waters north (ICN) of the St. Johns River (SJR), whereas 87 dolphins preferred estuarine waters south (ICS) of the SJR. Of dolphins with an ICN preference, 78% exhibited no preference for water season. In contrast, 93% of dolphins with an ICS preference exhibited cold season avoidance. Dolphins exhibited specific preference and avoidance patterns for specific habitat variables. Although undeveloped habitats comprised the majority of total area available within the ICN (94%) and ICS/SJR (54%) regions, less than 25 and 7%, respectively, of the dolphins preferred these ICN and ICS/SJR habitats. Regional, seasonal, and habitat variable preferences, such as those identified in this study, result in different levels to which highly mobile bottlenose dolphins may be affected by changes in habitat suitability. Lack of measurable fidelity observed for bottlenose dolphins sighted in alongshore coastal waters suggests reduced susceptibility of this community to anthropogenic habitat changes in northeastern Florida. In contrast, the highly philopatric nature of dolphins in the ICN increases their vulnerability to habitat changes and degradation. Seasonal use of the SJR and ICS regions of northeastern Florida, on the other hand, may mitigate the impact of habitat changes and degradation experienced by dolphins preferring these regions. [ABSTRACT FROM AUTHOR]