Spiky encounter proves too much for hungry shark

Former JCU PhD student Dr Nicolas Lubitz and his team were busy tagging marine life off the coast of Orpheus Island, north Queensland in May 2022 when the shark they caught regurgitated a dead echidna.

In what is believed to be a world-first discovery, Dr Lubitz said he could only assume the shark had nabbed the echidna as it swam in the shallows off the island or even between islands, which the monotremes are known to do.

“We were quite shocked at what we saw. We really didn’t know what was going on,” he said.

“When it spat it out, I looked at it and remarked “What the hell is that?”. Someone said to take a picture, so I scrambled to get my phone.

“I managed to only get one picture, but you can see the outline of the echidna in the water.”

Dr Lubitz said the dead echidna was still whole when it was regurgitated, suggesting it was only a recent kill by the three-metre-long shark.

“It was a fully intact echidna with all its spines and its legs,” he said.

“It was a decent-sized Tiger shark but it wasn’t massive. It’s very rare that they throw up their food but sometimes when they get stressed they can,” he said.

“In this case, I think the echidna must have just felt a bit funny in its throat.”

Known for their voracious appetites, Tiger sharks have been documented swallowing seabirds, tyres, license plates and even a small TV screen.

“It’s known that Tiger sharks will eat anything. They’re just a scavenger. I’ve seen videos of them eating a rock for no reason,” Dr Lubitz said.

The Tiger shark in question was unharmed during the bizarre encounter and was subsequently fitted with an acoustic tracker by the team before being released back into the water.

In another surprising find, a different Tiger shark caught and tagged by the team threw up half a dugong.

“It threw up a big piece of blubber and then a full vertebral column. I think it was a dugong calf it had a go at,” Mr Lubitz said.

The JCU team was part of a state-wide effort known as the Queensland Integrated Marine Observing System Acoustic Telemetry Array Project, which saw researchers tag marine life such as jewfish, snapper, mullet, Shovelnose rays and various species of sharks with acoustic and satellite trackers, as well as place acoustic receivers along the coast between 2020 and 2023 in order to gather data on marine life inhabiting each area.

To date, the project has tagged 812 animals with 10-year trackers from the Gold Coast up to the Torres Strait.

The Australian Institute of Marine Science, the Queensland Department of Agriculture and Fisheries’ (DAF) Shark Control Program, Queensland DAF Fish Aggregation Devices Program, JCU, the Department of Environment and Science, Biopixel Oceans Foundation, Parks Australia and University of the Sunshine Coast are involved in the project.

“There’s always been acoustic receivers along the Queensland coastline but they were sort of disconnected and weren’t picking up a lot of big movements,” Mr Lubitz said.

“With the Queensland Array, we’ve filled a lot of gaps and through that work we’ve picked up movements of species like Shovelnose rays travelling from Townsville to the Sunshine Coast, which people never thought were migratory at all.

“They’re a critically endangered species and we’ve caught and tagged some that are almost three metres long.”

Full data downloads from the acoustic array will become available later this year, allowing researchers the ability to analyse the migratory patterns of various marine species.