Long‐Term Dynamics of the Home Range and Community Structure of Bottlenose Dolphins in a Fast‐Developing Coastal Ecosystem in Southern Florida

ABSTRACT Investigating individual home ranges within animal populations is critical to understanding community dynamics and identifying the drivers of population structure and substructure. Anthropogenic impacts such as habitat modification can have significant effects on the home range of marine predators but have rarely been investigated in free‐ranging populations on a long‐term basis. In environments where habitat quality is degrading, home range size is expected to increase for large predators as they may need to travel farther to find food. Using photo‐identification data from 1999 to 2019 and kernel density estimates, we assessed the spatio‐temporal dynamics of home range, residency and community structure within a resident population of bottlenose dolphins in Biscayne Bay, a highly urbanized waterway off the coast of Miami, Florida. General and core home ranges were estimated from 95% and 50% utilization distributions (UD), respectively. Two distinct communities were identified: a northern community and a southern community. The southern community exhibited significantly larger home ranges (95% UD = 126.88 ± 93.45 km 2 , 50% UD = 32.54 ± 27.46 km 2 ) compared to the northern community (95% UD = 68.46 ± 56.55 km 2 , 50% UD = 17.0 ± 13.79 km 2 ). A temporal analysis revealed an overall contraction of core home range for both communities over the course of the study period, significantly decreasing by 36.2% in the northern community and 25.7% in the southern community. The contraction in home range is contrary to what we would have expected in a heavily impacted environment experiencing habitat degradation, where expansion might be necessary to locate sufficient prey. In this population, however, continued use of familiar areas may facilitate the exploitation of limited resources and minimize energy costs in expanding into less familiar territory. Additionally, given the confined geography of Biscayne Bay, a contraction may also reduce competitive interaction among communities through resource partitioning.