Scientists Finally Discovered What Ate a 20 Foot Great White Shark - And It Worse Than Anyone Image

Added: 2026-05-31

[00:00:00]Back in 2003, scientists working with Australia's National Science Agency, the Commonwealth Scientific and Industrial Research Organization, better known as CSIRO, tagged a fully grown female great white shark, near the southwest coast of Western Australia. The shark measured around 2.74 m long, or roughly 9 ft. She was healthy, mature, and exactly what researchers would expect from an adult female great white in that region. But what happened to this shark over the next few months would become one of the most terrifying mysteries ever recorded in marine science. And before we continue, make sure to subscribe to the channel and turn on notifications because the deeper this story goes, the more disturbing it becomes. The tagging was part of CSRO's long-running shark monitoring project launched in the early 2000s to better understand the movements and behavior of great white populations around Australia. At the time, the program was generating some of the most advanced predator tracking data ever collected in marine science. Attached to the shark was a satellite tracking device known as a PAT tag, short for popup archival transmitting tag. These devices are considered essential tools in large ocean predator research. They continuously record depth surrounding water temperature and light levels while attached to the animal. Unlike GPS trackers, however, PAT tags don't send live updates. Every piece of information stays stored inside the tag until it eventually detaches, rises to the surface, and uploads the data through the Argos satellite system. Because of that delay, researchers often don't see what happened to an animal until months after the events actually occurred. The shark, later nicknamed Alpha in documentary coverage years afterward, disappeared into the waters of the Indian Ocean, and the Southern Ocean along Western Australia's coastline. For months, everything appeared completely normal. She traveled across huge distances.

[00:02:26]She dived through deep water. She hunted and behaved exactly like countless other tagged great whites researchers had studied before. Meanwhile, the tag fixed near her dorsal fin silently logged every movement and environmental change in its memory. Then 4 months later, the tag suddenly resurfaced. It washed ashore near Bremer Bay, more than 500 km southeast of Perth on Australia's southern coastline.

[00:02:58]Its programmed release system had activated exactly as intended.

[00:03:04]Satellites detected the signal. The device was recovered and scientists downloaded 4 months of archived information. What they discovered inside that data stunned them. For most of the tracking period, the recordings showed ordinary great white shark behavior.

[00:03:23]Depth patterns matched known migration habits. Water temperatures reflected the cold southern ocean conditions Alpha had been swimming through. It looked like a perfectly routine scientific record.

[00:03:36]Then everything changed in a single moment. The first abnormal reading was a dramatic spike in temperature. Just before the event, the surrounding water at Alpha's depth measured around 7.8° C, about 46° F. typical icy southern ocean water. Then within minutes, the tag registered a sudden jump to approximately 25.5° C or around 78° F. That kind of increase simply does not happen naturally in deep open ocean water. The only environment capable of maintaining that level of warmth at depth is the inside of a massive living animal. The tag had been swallowed, but the temperature change was only the beginning. Immediately afterward, the tracking data showed a rapid descent. Whatever creature had consumed Alpha Dove from near surface waters down to almost 580 m, around 1,900 ft, in a surprisingly short amount of time. The movement pattern didn't resemble the normal diving behavior of a great white shark. Instead, it matched the behavior of a much larger predator descending deliberately after feeding.

[00:04:59]For hours, the tag remained deep underwater while still recording the same elevated internal temperature.

[00:05:06]Conditions consistent with being inside the stomach of a huge animal actively digesting food. Eventually, the creature returned toward shallower water. At some stage, the tag passed through the digestive system, either expelled or regurgitated before drifting back toward the ocean surface. Later, the programmed release activated. The satellites picked up the signal and the device finally ended its journey on a beach near Bremer Bay. The evidence in the recordings was impossible to ignore. The temperature pattern was unmistakable.

[00:05:47]The dive profile was unmistakable, and the extended period spent inside that heated environment left little room for doubt. Alpha, a healthy adult 9- ft great white shark, had been eaten. For years, the case remained mostly within scientific circles. Shark researchers discussed it at conferences and referenced it in studies examining predator on predator attacks in the ocean. Scientists were slowly building a larger picture of interspecies predation using stomach content evidence, field observations, and additional tagging research. But the story didn't truly reach the public until 2014.

[00:06:32]That was when Australian filmmaker David Riggs released a Smithsonian Channel documentary called Hunt for the Super Predator. The documentary introduced the phrase that would become forever linked to the mystery, the colossal cannibal great white shark. One of the leading scientific experts featured in the film was John McCoscer, senior scientist at the California Academy of Sciences and one of the world's most respected authorities on great white sharks. John McCusker's interpretation of the evidence along with the documentary's central theory ultimately pointed toward one clear conclusion about what killed Alpha. The predator was most likely another great white shark, but not just any great white. According to the data, the animal was estimated to be around 5 m long, roughly 16 ft, and likely weighed over 2 tons. Researchers believe it attacked Alpha suddenly, killed her almost instantly, swallowed her, and then descended nearly 1,900 ft into deep water while digesting the meal. That explanation fits the evidence remarkably well. Yet, it's not the version of the story that captured the internet's imagination.

[00:07:56]Over the years, the alpha case became surrounded by speculation that something far more mysterious was responsible.

[00:08:04]An unknown deep sea apex predator, perhaps even a surviving megalodonike creature hidden in the ocean depths.

[00:08:12]That theory generated headlines, clicks, and endless online discussion. But it's not what the scientific evidence actually supports. And the reason scientists ruled out those more sensational explanations are what make the real answer so fascinating on its own. One of the first alternative suspects researchers considered was orcas. Killer whales are absolutely capable of hunting great white sharks.

[00:08:41]In fact, modern evidence has proven this beyond dispute. The clearest example came in 2017 near Gansbai, South Africa.

[00:08:52]one of the world's most famous great white shark hotspots. Two great whites washed ashore there with an incredibly unusual injury pattern. Their livers had been removed with surgical precision.

[00:09:05]Later, forensic analysis linked the attacks to two male orcas known as port and starboard. The impact was dramatic.

[00:09:13]After the killings, local great white populations abandoned the region for unusually long periods.

[00:09:21]Just the presence of those orcas appeared capable of reshaping shark behavior across the entire area. So yes, orcas are genuine predators of great white sharks. And in many ways, Alfa's death resembled an earlier, less documented version of the same predator prey relationship that later became world famous in South Africa. But when researchers examined the data closely, the orca explanation stopped fitting.

[00:09:51]The biggest problem was temperature.

[00:09:54]Orcas are mammals, meaning they maintain a warm and stable internal body temperature of around 36 to 37° C, approximately 97 to 98° F. But after alpha disappeared, the tag recorded an internal temperature of only 25.5° C or 78° F. That's far too cold for the inside of an orca. If the tag had entered a killer whale's stomach, the readings should have been much closer to mamalian body temperature, near 98° F.

[00:10:33]Instead, the data pointed somewhere else entirely. A temperature around 78° F is actually consistent with the body temperature of a large predatory fish.

[00:10:45]Great white sharks aren't fully coldblooded like most fish species. They possess a specialized adaptation called regional endothermia, which allows certain parts of their bodies, especially muscles and digestive organs, to stay significantly warmer than the surrounding water.

[00:11:04]Large great whites commonly maintain internal temperatures ranging from around 14 to 25° C. That aligns almost perfectly with what Alpha's tag recorded. Then there was the depth data.

[00:11:20]After the attack, the tag descended to roughly 580 m. While orcas can perform deep dives, their hunting dives are generally much shallower than this.

[00:11:32]Sustained dives approaching 1,900 ft are unusual for killer whales. For great whites, however, those depths are entirely within documented behavior.

[00:11:44]Other shark tagging studies have recorded great whites diving just as deep, sometimes even deeper. The final clue came from the feeding pattern itself. Orca attacks on great whites tend to follow a very specific strategy.

[00:12:02]As seen in the Gansai incidents, killer whales often immobilize sharks and target the liver specifically because it's rich in energy dense fats. The rest of the shark's body is frequently left mostly intact. That's not what happened to Alpha. She wasn't partially eaten.

[00:12:21]She appears to have been swallowed whole or nearly whole. The tracking tag remained inside the predator for hours, recording digestive conditions that simply don't match the feeding style observed in orcas. This is why the documentary's conclusion wasn't based on wild speculation.

[00:12:40]It came from three separate lines of evidence, all pointing toward the same answer. Temperature, dive behavior, and feeding pattern. Every one of them indicated the same predator. A massive great white shark hunting another member of its own species. And honestly, that reality is already terrifying enough without needing to invoke prehistoric monsters.

[00:13:07]The largest reliably confirmed great whites ever measured reach around 6 m or close to 20 ft in length. The predator believed to have killed alpha, estimated around 16 ft, falls completely within the known size range of the species.

[00:13:26]No undiscovered creature is required to explain the event. No surviving megalodon, no hidden species lurking in the abyss.

[00:13:37]just an exceptionally large great white shark operating at the upper limits of what nature already produces. And we know sharks that size exist because humans have actually filmed them. The most famous example is a giant female known as Deep Blue. First documented near Guadalupe Island off the coast of Mexico around 2013 and 2014, Deep Blue measures roughly 6.1 m long, about 20 ft. Deep Blue, one of the largest verified great white sharks ever filmed, proves that 20ft giants are real.

[00:14:18]Researchers believe she may be around 50 years old, and footage captured by divers confirmed her enormous size.

[00:14:26]And according to the alpha evidence, a shark similar to deep blue may have attacked and swallowed a 9- ft female great white in a single strike deep beneath the waters of Western Australia.

[00:14:38]No cameras recorded it. No humans witnessed it. Only the tracking tag survived to tell the story. That's what makes the alpha case so disturbing. If the tag had never resurfaced, nobody would have known anything happened at all. The incident also revealed something scientists are still trying to understand.

[00:15:00]Giant great whites may prey on smaller members of their own species far more often than previously believed. And alpha was not a juvenile. She was a fully grown adult apex predator, but something nearly twice her size still hunted her. Anyway, at 9 ft long, Alpha was a fully developed adult female, already an apex predator herself, capable of hunting powerful prey and surviving in one of the ocean's harshest ecosystems.

[00:15:32]By any normal standard, she was already dangerous, and yet another member of her own species still hunted and consumed her with apparent ease. As far as published scientific literature currently shows, the alpha case represents the first documented predation event involving a tagged adult great white shark. The famous orca attacks in South Africa that occurred in 2017 became the second major category of documented large predator attacks on adult great whites. Between Alpha's disappearance and the Gunspy incidents, more than 10 years passed without another similarly documented event entering the scientific record. That gap could mean these attacks are genuinely rare. Or it could simply reflect how incredibly difficult it is to witness such an event in the open ocean, especially when the only observer is a tracking device attached to the victim.

[00:16:31]Most likely, it's a combination of both.

[00:16:35]What the evidence does not suggest is the presence of some mysterious undiscovered predator. Everything recorded by Alpha's tag fits within the known biological capabilities of great white sharks. Nothing in the data requires inventing an unknown species to explain it. And this is where a principle like Aam's razor becomes important. The simplest explanation, the one requiring the fewest assumptions, is another great white shark. Not a hidden monster, not a surviving megalodon, just an exceptionally large individual of a species we already know exists. And scientifically, that explanation fits perfectly. To be clear, Megaladon itself was absolutely real. The prehistoric shark known as Otus Megalodon is supported by an enormous fossil record found across the globe. Its giant teeth continue to be discovered in coastal deposits and dredged from continental shelves even today. But all evidence indicates the species disappeared around 3.6 million years ago during the end of the Pioscene epic. Researchers know this from multiple independent sources.

[00:17:55]fossil dating, isotopic analysis, and the complete disappearance of Megalodon remains from younger sediment layers worldwide.

[00:18:05]There's another important detail often ignored in popular theories. Megalodon was not a deep sea animal. The fossil evidence places it primarily in warm coastal environments where large marine mammals, especially ancient whales, were abundant. The modern idea that Megaladon somehow escaped extinction by retreating into the deep ocean actually conflicts with everything scientists understand about its ecology. The deep sea is cold, dark, and relatively poor in food resources. It supports certain specialized predators like sleeper sharks, six gill sharks, and deep water squid, but nothing remotely approaching megalodon in size. In fact, the largest known deep sea predatory fish are dramatically smaller than megalodon by an entire order of magnitude. There's currently no known ecological niche in the modern deep ocean capable of supporting a hidden population of giant super predators. And if such animals existed, scientists would expect to see evidence. Massive bite marks on whale carcasses, strange prey population collapses.

[00:19:21]unexpected remains washing ashore. But none of those signatures exist. Now, it's true that much of Earth's oceans remain poorly explored. Around 80% of the seafloor has still not been mapped in high resolution, and only a small percentage of the total ocean volume has ever been visually surveyed by humans or remotely operated vehicles.

[00:19:47]Those numbers are real. And every year, researchers continue discovering new marine species. But the kinds of animals being discovered matter. Most newly identified ocean species are tiny.

[00:20:01]Microbes, small invertebrates, deep sea fish, or animals previously mistaken for already known species. The discovery of entirely new apex predator classes is extraordinarily rare. In fact, the last major marine predator of that scale discovered by science was the mega mouth shark in 1976.

[00:20:24]And even that species isn't a top predator. It's a massive filter feeder.

[00:20:30]Since its discovery, mega mouth sharks have already been observed more than 250 times around the world. That pattern simply doesn't support the idea of a hidden megalodonized hunter escaping detection in modern oceans.

[00:20:45]What it does support is the continued discovery of small and obscure life forms living in the planet's least explored ecosystems.

[00:20:53]And honestly, the real conclusion behind Alpha's story may be more unsettling than the fantasy version. Because the truth suggests that the ocean's most feared predator has competition from its own kind. At the extreme upper limits of their size range, adult great whites occasionally appear capable of hunting and consuming other adult great whites.

[00:21:18]These encounters happen far below the surface beyond the reach of cameras, divers, and almost every monitoring system humans currently rely on. Unless one of the sharks involved happens to carry a tracking device, the event leaves virtually no trace behind. And at any given moment, only a tiny fraction of the global great white population is tagged. The truly massive 20ft individuals are also extremely rare.

[00:21:49]Sharks like deep blue become famous precisely because animals of that size are encountered so infrequently.

[00:21:57]Most giant great whites have likely never been filmed. Many have never been tagged. And somewhere in the dark, cold waters beyond human observation, some unknown number of those enormous sharks occasionally encounter smaller members of their own species and treat them exactly the same way a great white treats any other prey animal. When events like this happen, the pattern is chillingly similar to what Alpha's Tag recorded in 2003.

[00:22:29]First came the sudden temperature spike, then the rapid dive into deep water. For hours, the tag remained inside a predator's digestive system before eventually being expelled and washing ashore months later, carrying the only evidence the attack had ever happened.

[00:22:48]What scientists still don't know is how often this occurs. The alpha case proved one terrifying reality. Giant great whites sometimes hunt and eat smaller great whites of their own species. Alpha was not a juvenile. She was a fully grown 9- ft apex predator, and something nearly twice her size still killed and swallowed her whole. For decades, great whites have been portrayed as the uncontested rulers of the ocean. But the alpha case revealed a darker truth within their own species. There is another hierarchy. A 20ft giant, great white, may see a smaller adult shark the same way that shark sees a seal. And unlike the megalodon theories that later spread online, the evidence points towards something far more real and scientifically supported. Not a hidden prehistoric monster, just an enormous great white shark operating at the extreme limits of what the species can do. The most unsettling part is that encounters like this almost certainly happen far more often than humans ever witness.

[00:24:04]Most occur deep underwater, far from cameras, divers, or tracking systems.

[00:24:11]The ocean didn't reveal an unknown predator. It revealed how little we truly understand about one we already know exists. The shark carrying the tag was 9 ft long. The shark that ate her was roughly twice that size. And they were the same species.