Tiger Shark Regurgitates An Echidna In A World-First Event
In a once-in-a-lifetime discovery, a team of researchers from James Cook University witnessed a tiger shark regurgitate an unusual snack choice: an echidna. Also known as spiny anteaters, these iconic monotremes are native to Australia and New Guinea. Characterized by their unique combination of mammalian and reptilian features, including spines covering their backs and a long, sticky tongue used to capture ants and termites (their primary food sources), these animals are typically found in terrestrial environments such as forests, grasslands, and deserts. Plainly put: echidnas are not aquatic animals and are rarely encountered near marine habitats. So seeing a tiger shark spit one up was highly unusual... and extremely unexpected.
Named for their distinct vertical stripes resembling a tiger's pattern, tiger sharks (Galeocerdo cuvier) are notorious for their indiscriminate and rather eclectic eating habits, earning them the moniker "garbage cans of the sea." The apex predators have been documented consuming a wide array of unusual items beyond their typical prey such as tires, license plates, TNT, chicken wire, and more. Their voracious appetite and ability to consume almost anything just goes to show they are truly opportunistic scavengers in marine ecosystems, adapting to diverse environments and food sources with surprising versatility.
Dr. Nicolas Lubitz and his team were in the midst of their research, focusing on tagging various marine species, off the coast of Orpheus Island in north Queensland, when they caught the almost 10 foot long (three meter long) tiger shark. What happened next left them stunned. "We were quite shocked at what we saw. We really didn't know what was going on," Lubitz recounted. "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."
The dead echidna was intact when it was regurgitated, indicating it was a recent kill. "It was a fully intact echidna with all its spines and its legs," Lubitz said. The shark's behavior of regurgitating its meal is rare but not unheard of . While regurgitation is not common among all sharks, it occasionally happens as a natural response to various internal or external stimuli affecting the shark's feeding process. "It's very rare that they throw up their food, but sometimes when they get stressed they can. In this case, I think the echidna must have just felt a bit funny in its throat."
Despite the bizarre encounter, the tiger shark seemed okay. The team fitted it with an acoustic tracker before releasing it back into the ocean. But did the echidna's spines harm it? Many predators have specialized digestive systems that can handle tough or spiny prey, with powerful stomach acids or enzymes that can break down spines or other tough structures. While tiger shark stomachs are tough, their ability to effectively consume such bizarre prey - equipped with such big defensive spines - is not well known. Afterall, it's not like the ocean is full of echidnas for them to munch on! Perhaps it regurgitate the small animal to avoid potential internal injury? Unfortunately, at this time, we don't have an answer.
But, the incident with the echidna was not the only strange find during their research! Another tiger shark caught by the team regurgitated half a dugong, also equally unexpected. "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," Lubitz explained.
The JCU team's research is part of a larger initiative, the Queensland Integrated Marine Observing System Acoustic Telemetry Array Project; this project aims to tag and track marine life such as jewfish, snapper, mullet, shovelnose rays, and various species of sharks. By placing acoustic receivers along the Queensland coast, the researchers have been gathering data on the movements and behaviors of these animals. To date, the project has tagged 812 animals with 10-year trackers, covering areas from the Gold Coast up to the Torres Strait. The project involves multiple organizations, including the Australian Institute of Marine Science, the Queensland Department of Agriculture and Fisheries' (DAF) Shark Control Program, the Queensland DAF Fish Aggregation Devices Program, JCU, the Department of Environment and Science, Biopixel Oceans Foundation, Parks Australia, and the University of the Sunshine Coast. "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," Lubitz explained. "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."
One significant finding from the overall project is the migratory behavior of shovelnose rays, a critically endangered species. "They're a critically endangered species and we've caught and tagged some that are almost three meters long," Lubitz said. The full data downloads from the acoustic array will become available later this year, allowing researchers to analyze the migratory patterns and other behaviors of various marine species.
