Evaluating movement patterns of common bottlenose dolphins using cookiecutter shark bite wounds in the Mississippi Sound

Abstract

Common bottlenose dolphin stocks are delineated by location endpoints and depth contours. These boundaries reflect the best understanding of stock spatial distribution at the time of delineation, but may need adjustment over time for appropriate management and conservation of the species. Natural interactions between bottlenose dolphins and species with restricted ranges can provide insights into spatial habitat use. As cookiecutter sharks are a deepwater species, and estuarine bottlenose dolphin stocks are considered to be restricted to shallower waters, their habitats are not typically considered to overlap. Here we detail twelve novel examples of bottlenose dolphins photo‐identified in estuarine waters with cookiecutter shark bites in various healing stages. Bites on two pantropical spotted dolphins that stranded in Mississippi support the presence of cookiecutter sharks in local deep waters, suggesting that the dolphins move across established stock boundaries. These movements are likely seasonal as open cookiecutter wounds varied significantly by season and were more likely to be seen in winter and spring months (p = 0.03), correlating with seasonal abundance trends. Even resident dolphins with high site fidelity may have home ranges that span multiple stock areas as one such bottlenose dolphin was also documented with a cookiecutter shark bite. These natural interactions provide evidence of dolphin movement, as well as insights into how these stock boundaries can be evaluated in the future.