Battle scars: Sharks leave their mark on dolphin species

A new study has revealed the frequency of shark attacks on dolphins along the Queensland coast, with about 25 per cent showing signs of injuries.

May 23, 2023, updated May 23, 2023
An Australian humpback dolphin. (Image: Daniele Cagnazzi)

An Australian humpback dolphin. (Image: Daniele Cagnazzi)

Marine mammal experts from Flinders University and around Australia found about a quarter of snubfin and humpback dolphins studied near Gladstone, Bowen and Townsville had suffered shark attacks.

The study assessed thousands of photos taken from boat-based surveys which revealed evidence of shark bites, providing new insights into failed predation attempts.

It showed increased attacks on dolphins in northern Queensland, increased predation closer to the coast and equal attacks between the two species.

“This study is the first to assess the occurrence of shark-bite scarring on snubfin and humpback dolphins in Queensland across different group sizes, habitat features, and locations, and serves as a baseline for shark-dolphin interactions in the area,” said Caitlin Nicholls from the Cetacean Ecology, Behaviour and Evolution Lab at Flinders University.

“These results highlight the importance that habitat features could have in predation pressure of dolphins, as well as the importance of considering photographic coverage when assessing bite injuries on animals.”

Snubfin and humpback dolphins are listed as vulnerable species by the Queensland Nature Conservation Act.

There are small numbers in northern Australian waters with low genetic diversity and slow reproduction.

Lead researcher, Associate Professor Guido Parra, said the presence of shark-inflicted wounds and scars on live individuals could provide an indirect measure of predation pressure and the frequency of shark attacks.

“Predation and predation risk have a large influence on the ecology and evolution of both predator and prey species,” he said.

“To decipher how communities are structured and function, we need to understand how predators and prey interact.”

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