The previously unknown behaviour was discovered by a team of researchers, including scientists from the University of Edinburgh, studying sandbar sharks in the Mediterranean Sea.
Taking cover
Underwater video footage captured by divers and remotely operated vehicles shows a type of small predatory fish – called blue runners – using the sharks for cover while they hunt.
Previous research has shown that some fish shadow sharks to remove parasites and hide from predators. However, they have never before been seen hiding behind sharks to ambush their prey.
Attack strategy
Videos captured off the coast of Italy’s Lampione Island revealed 34 examples of blue runners using this hunting strategy. On each occasion, a single fish shadowed a shark for around 30 seconds before breaking off to launch high-speed attacks on smaller types of fish, such as damselfish.
Analysis of the footage suggests that the fish – which usually hunt in small groups – are more likely to catch their prey off guard by shadowing sharks, increasing their chances of success, the team says.
When hiding behind a shark, prey only noticed a blue runner’s approach around 10 per cent of the time. In contrast, when the fish hunted in packs their prey spotted them almost every time – more than 95 per cent of attacks – and got into a defensive schooling formation.
Seeking protection
As well as improving their chances of a successful hunt, the shadowing behaviour may protect blue runners from their own predators and help them conserve energy by swimming in sharks’ slipstream, the team says.
The research is based on multi-year observations around Lampione Island, where a rare clustering – known as an aggregation – of sandbar sharks occurs every summer.
The study, published in the journal Ecology, was supported by the Blue Marine Foundation and National Geographic Society. It also involved researchers from Stazione Zoologica Anton Dohrn, the National Biodiversity Future Center, CNR-IAS and the University of Palermo.