Poster Australian Marine Sciences Association 2022

Incidence of shark bites on Australian humpback (Sousa sahulensis) and snubfin (Orcaella heinsohni) dolphins along the east coast of Queensland, Australia. (#530)

Caitlin R Nicholls 1 , Katharina J Peters 2 3 , Daniele Cagnazzi 4 , Daniella Hanf 1 5 6 , Guido J Parra 1
  1. Cetacean Ecology, Behaviour and Evolution Lab, College of Science and Engineering, Flinders University, Adelaide 5001, SA, Australia
  2. Cetacean Ecology Research Group, School of Natural and Computational Sciences, Massey University, Auckland 0745, New Zealand
  3. Global Ecology, College of Science and Engineering, Flinders University, Adelaide 5001, SA, Australia
  4. Faculty of Science and Engineering, Southern Cross University, Lismore 2480, NSW, Australia
  5. O2 Marine, Busselton 6280, WA, Australia
  6. Centre for Sustainable Aquatic Ecosystems, Harry Butler Institute, Murdoch University, Murdoch 6150, WA, Australia

Predation risk is a major driving force in the ecology, evolution, population dynamics, and community structure of animals. Sharks are important predators of dolphins, with dolphins often bearing shark bite scars as evidence of predator-prey interactions. In this study, we used photo-identification data to investigate the frequency of shark-inflicted wounds on sympatric Australian humpback (Sousa sahulensis) and snubfin (Orcaella heinsohni) dolphins across three sites in Queensland, Australia. We assessed if shark bite prevalence varied between species and in relation to site, shark relative abundance, group size, and environmental variables (i.e. water depth, distance to estuary and distance to coast). Of the 408 photo-identified humpback dolphins, 30% bore shark-inflicted scars, compared to 37.5% of the 284 snubfin dolphins. Generalised additive models indicated that incidence of shark bite presence varied between species and was influenced by distance to estuary, shark relative abundance, and photographic coverage of each individual, suggesting that dolphins using water close to estuaries and areas with high relative abundance of sharks are potentially subject to higher predation risks. This study provides a valuable baseline for future studies into shark/dolphin interactions, factors influencing predation risk, and the role of predation in the evolution of delphinids behaviour and ecology.