Community-Level Variation in the Trophic Interactions of Common Bottlenose Dolphins, Tursiops truncatus, Experiencing a Reduction of Their Foraging Habitat

Abstract

The influence of habitat degradation on the trophic interactions of marine predators remains poorly understood. We investigated the foraging ecology of resident common bottlenose dolphins (Tursiops truncatus) in Biscayne Bay, Florida, which has experienced extensive seagrass loss since 2010. Using stable isotope analysis (δ13C and δ15N) of dolphin skin tissue and Bayesian mixing models (“SIBER” and “MixSIAR” packages in R), we compared foraging habitat and prey preferences of two dolphin communities exposed to differing levels of anthropogenic impact. The mixing models indicate that foraging habitats and food sources are significantly different between communities. Dolphins from the northern community, situated in a highly urbanized area with severe habitat degradation, primarily relied on pelagic prey, while dolphins from the southern community, where habitat degradation is less severe, primarily foraged on seagrass-associated prey. The drivers of spatial differences in foraging habitat preferences and diets are unclear but could reflect the availability and predictability of food sources in pelagic vs. seagrass-associated habitats in Biscayne Bay. Despite these challenges, the dietary plasticity demonstrated by both communities suggests a potential adaptive response to habitat decline. However, dolphins from the northern community may face higher risks due to their proximity to intense anthropogenic activity.