Unveiling the Ocean's Curiosities: The Case of the Tiger Shark and the Intact Echidna

Once the spiny creature cleared the gills, the creature spat out the echidna whole. And as you would respond to such an incredible scene, the marine researchers were stunned. Imagine eating your lunch and spitting out a somewhat snarled, hairy, prickly leg lizard still alive. This was bizarre, and a researcher on board that momentous day would later say the shark unloaded the echidna as if ‘it had peanut butter in its mouth’. But for marine researchers, that bizarre event barely scratched the surface of what a tiger shark would eat. Tiger sharks are wide ranging, complex and voracious coastal predators. They feed on fish, mammals, crustaceans, seabirds, reptiles, marine birds, amphibians, cephalopods, and even other sharks. So, the echidna spat story is relatively low on a list of strange commensalities, or shared meals. But these particular beasties do remind us of the open-mindedness of one of the oceans most curious and beautiful creatures, the tiger shark.

The Encounter That Opened Eyes

The Unexpected Meal

One day, while conducting a tagging expedition to study tiger shark movements and behaviours, the biologist Nicolas Lubitz and his team were working on catching a seemingly ordinary tiger shark when the shark vomited up an echidna. Yep, you read that right, a spiny monotreme was suddenly being sprayed out of the tiger shark’s mouth. Echidnas are known to venture and swim shallow waters, but they’re not often found in the stomach of marine predators.

The Open Appetite of Tiger Sharks

After all, tiger sharks are known as food-vacuum cleaners, having swallowed everything from motorcycle licence plates to, yes, other sharks. Yet the echidna’s expulsion suggests that in ingurgitation some limit must lurk. This particular tiger shark, which was about 10ft in length, illustrated that in the marine world size isn’t always a limiting factor when it comes to the menu. But maybe some snacks are more bother than they are worth.

The Eclectic Diet of Tiger Sharks: An Open Menu

A Predator's Open-mindedness

This openness to experimentation with food choices – even if one’s choices turn out to be indigestible – is reflected in the phrase ‘they eat almost anything they can get their jaws around’. And it wasn’t only the echidna that the tiger sharks tossed back indigestible; another of the team’s tiger sharks, tagged a week after the echidna incident, vomited up the remains of a dugong.

Open Seas, Open Stomachs

In fact, the ocean conservancy’s reports echo the findings of Nicolas Lubitz and his team. Tiger sharks’ stomachs have contained everything from the inanimate to the unexpected, including tires, license plates and, incredibly, other sharks. There is nothing shy about their appetite, but the echidna-in-tact suggests that there are limits to their culinary adventures.

The Survivor and the Expelled: Lessons from the Deep

The Echidna's Untimely End

An echidina found its way into a tiger shark that bit it off and died of some unknown cause. With indigestion that’s not apparent from the stomach’s contents, it’s easy to see how the tiger shark might have spit out partially digested food, but why would it have spit out the echidina whole? Was it that spiny exterior that sent the shark fleeing, or just a bad tasting bite? Whatever the cause, the tiger shark lived on – perhaps a little wiser about who its next meal should be.

The Open Ocean's Unpredictable Diet

This incident is a reminder of the fickle, sometimes fecal, fare of marine predators, and how quickly they’ll snap their jaws shut, and why they need to.

The Open Nature of Discovery

Mysteries Unfold

When a tangled, fully formed echidna turns up regurgitated from the belly of a tiger shark, you get more than just a strange tale of strange animal feeding habits. You get a view of sea mysteries that have yet to be revealed. Scientists such as Nicolas Lubitz and his cohort are the people who give us these stories. They are the ones who peel back the veil on lives so different, but still filled with animals that we can relate to.

Unraveling the Open Secrets

The ocean is a storybook waiting to be read, its mysteries revealed little by little, each contact, each anomaly, each surprise enriching our wonder and stimulating the search for knowledge. In exploring the deep ocean, new encounters continue to remain open to the lessons of this ancient world.

About Open

And here is the deep meaning of ‘open’ that I want to use now. So much of a shark is open: the abyss of its gaping mouth, the unknowateachable black maw of its spiralling gut, the forever underwater, pressurised permeability of its skin, the free-fall of its swift, sinuous action. And being open is exactly what it takes to do research and enquiry, to be able to see what the world reveals, the deep pattern of life through each creature – a tiger shark stumbling on an echidna’s spine. Open is what it takes to be curious, tough, nimble – alive – in the most unexpected ways.

As we open ourselves up to this unknown, we discover new things about how the natural world works, and hopefully also find new things we can love in the process.

Jun 08, 2024
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