A group of Australian scientists studying marine life off the coast of Queensland were in for quite a surprise: a tiger shark that had regurgitated a spiny urchin-like animal called an echidna. Former James Cook University PhD student Nicolas Lubitz and his team spotted the potential for regurgitation during a tagging trip in May 2022 and the discovery is believed to be a world first. The team believes the shark acquired the echidna while swimming in the shallow water off the island or even between islands.
“We were quite shocked by what we saw. We really didn't know what was going on.” Lubitz said in a statement. “When he spit it out, I looked at it and said, 'What the hell is that?'. Someone told me to take a picture, so I rushed to get my phone. I was only able to take one photo, but you can see the outline of the echidna in the water.”
The dead echidna was still whole when the tiger shark regurgitated it, with its spines and legs still intact. This suggests it was a recent snack for the approximately 3-meter-long shark.
“It was a pretty big tiger shark, but it wasn't huge. It's rare for them to throw up their food, but sometimes when they get stressed they can,” Lubitz says. “In this case, I think the echidna just felt a little strange in its throat.”
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Many animals may vomit after ingesting something they shouldn't. Whale barf in other words ambergris has even been used in perfumes, medicines and spices during the heyday of commercial whaling. rodents, frogsAnd horses are some notable exceptions to the fallow rule. Instead, rodents typically eat non-nutritive substances, such as clay and dirt, to help out dilute the toxins instead of expelling them from their bodies. Frogs maybe even eject their entire stomachs instead when they inject something poisonous.
Tiger sharks are known for this voracious appetite and are some of the the ocean's most avid scavengers. According to Lubitz, they have been documented swallowing seabirds, tires, license plates and television screens. The tiger shark was unharmed during the strange encounter and was also fitted with an acoustic tracker before the team released it back into the water.
In a separate find, another tiger shark that the team had previously tagged vomited what looked like half a dugong.
“A big chunk of blubber came out and then a full spine. I think it was a dugong calf that it was dealing with,” Lubitz said.
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The scientists were part of the Queensland Integrated Marine Observing System Acoustic Telemetry Array Project. Researchers have tagged a variety of marine life including snapper, mullet, shovelnose rays and several species of sharks with acoustic and satellite trackers. They also placed acoustic receivers along the Queensland coast between 2020 and 2023 to collect data on the marine life that lives there. To date, the project has tagged 812 animals with 10-year trackers from the Gold Coast north to the Torres Strait. Complete data downloads from the array will be available by the end of this year.
“There have always been acoustic receivers along the Queensland coastline, but they were more or less disconnected and didn't pick up a lot of big movements,” says Lubitz. “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 traveling from Townsville to the Sunshine Coast, which people never thought were migrating in the first place. It is a critically endangered species and we have captured and tagged some that are almost three meters long [9.8 feet] long.”
