The estuarine waters of the St. Johns River in Jacksonville, FL provide critical habitat for Atlantic bottlenose dolphins (Tursiops truncatus). However, due to the urban location of this community the risk of anthropogenic (human) disturbance is high. In September 2010, an Unusual Mortality Event (UME) was declared for Jacksonville’s estuarine dolphins in response to an unprecedented number of dolphin strandings/deaths in the St. Johns River. Unfortunately, the investigation into potential causes for these strandings was inconclusive due to limited knowledge of this community at that time. Our UNF Dolphin Research Program, initiated in March 2011, has strived to fill this knowledge gap through a systematic study of the behavioral ecology of the dolphins that inhabit the St. Johns River in Jacksonville, Florida.
Through weekly vessel-based photo-identification and behavioral surveys, our research team has identified over 520 individual dolphins in the St. Johns River (SJR). Dolphins are consistently sighted throughout our survey route, Mayport inlet to downtown Jacksonville, approximately 40 km up-river. Contrary to previous reports from the 1990’s, the SJR provides significant year-round habitat for a resident community of dolphins. In the past seven years, our team has developed a long-term photographic catalog and sighting history database of individual dolphins that we can use to address numerous research questions. For example, these data have enabled us to 1) identify critical habitat areas used for resting, mating/calving and foraging, 2) determine site fidelity and seasonal movement patterns, and 3) calculate life history parameters, particularly those related to reproductive success (e.g., calving rates, inter-birth intervals, and calf survival), as these are important indicators of the health and sustainability of the population. We routinely provide summaries of our findings directly to management agencies as these data are critical for assessing the potential impact of anthropogenic disturbance on this dolphin community.
As founding members of the Northeast Florida Dolphin Research Consortium, we are also working collaboratively with eight other research groups to determine the population abundance of estuarine bottlenose dolphins throughout the northeast Florida region (Fernandina Beach to Ponce Inlet). To do so, we conduct synoptic abundance surveys each summer and winter. Participation in this large-scale effort will clarify the larger ranging patterns of the St. Johns River dolphins, and thereby their cumulative exposure to anthropogenic disturbance.
In addition to the management oriented population monitoring work described above, another area of focus for our lab is social structure (association patterns) and complexity (e.g., male mating strategies). Our research has documented that some male SJR dolphins exhibit an exceptionally rare mating strategy, multi-level alliances, in which pairs of males cooperate with one another to obtain greater access to females. We are currently working to better understand the selection pressures that might have led to increased social complexity in this dolphin community. In the near future, we intend to expand the behavioral component of our research by investigating maternal care strategies and calf development.
Note: All research is conducted under authorization from NOAA Fisheries (GA LOC 14157 and Permit 18182) and UNF IACUC.