Investigating the Predation Risk of Coastal Dolphins via the Presence of Shark Bite Scars Across Southeast Queensland, Australia.

Predation and its risk influence the ecology and evolution of both predator and prey species. Despite this, predatory attempts of large apex sharks on cetaceans often remain unobserved, constraining empirical assessments of their frequency and ecological significance. Shark bite scars can be used as an indirect measure to quantify predation risk on dolphins and may reveal species-specific and spatial patterns of predator-prey interactions. Here, we analysed photographs of coastal dolphins in southeast Queensland, Australia to compare predation risk between multiple dolphin species across differing habitats. Using fresh wounds, bites were mainly attributed to tiger (Galeocerdo cuvier) and white (Carcharodon carcharias) sharks, with the peduncle being the most bitten body region across all species. Shark bite scarring differed between species: 50.3% of Australian humpback (Sousa sahulensis), 27.7% of Indo-Pacific bottlenose (Tursiops aduncus) and 38.5% of common bottlenose (Tursiops truncatus) exhibited scars. Dolphins had more scars in sheltered waters (42.6%) compared to open waters (16.3%). Generalised linear models confirmed S. sahulensis were more susceptible to predation attempts, with non-calves in sheltered waters most at risk. These findings provide a baseline for current predation risk across multiple habitats of sympatric dolphin species in Queensland, providing insight into drivers of the predator-prey interactions.