The Corkscrew Killer: The True Culprit Behind the Gruesome Seal Deaths Revealed

Scientists have identified the Greenland shark as the predator responsible for the mysterious “corkscrew” wounds found on dead seals on Sable Island, Nova Scotia. The findings, detailed in a study published in the journal Science in May 2026, resolve a decades-long biological mystery regarding the cause of gruesome injuries to local seal populations.

Sable Island, a remote and uninhabited sandspit located in the North Atlantic off the coast of Nova Scotia, Canada, serves as a critical habitat for grey and harbour seals. For several decades, researchers monitoring these colonies reported the discovery of seal carcasses washed ashore with highly unusual injuries. These wounds consisted of deep, spiral-shaped cuts that wrapped around the bodies of the animals, earning the unknown attacker the nickname “the Corkscrew Killer.”

The injuries were characterized by their surgical precision and a distinct lack of jagged edges or typical puncture wounds associated with many shark species. In many cases, the blubber layer was torn away in a twisting motion, even while the overlying fur remained largely unbroken. These patterns led to various theories over the years, including the possibility that the seals had encountered ship propellers or other man-made hazards.

The Role of Environmental DNA

The breakthrough in identifying the predator came through the use of environmental DNA (eDNA) analysis. Researchers collected water samples and tissue from the affected areas to detect genetic material left behind by predators. This non-invasive method allowed scientists to identify the presence of species that are rarely seen by humans and difficult to track in the deep, cold waters surrounding the island.

The genetic evidence pointed directly to the Greenland shark, a deep-water species known for its extreme longevity and preference for Arctic and North Atlantic waters. While the Greenland shark is a known predator, its specific role in the Sable Island deaths had remained speculative until the eDNA results provided a definitive link between the shark’s presence and the site of the attacks.

Mechanics of the Attack

The study explains that the “corkscrew” effect is a result of the Greenland shark’s unique hunting and feeding behavior. Unlike faster, more agile sharks that rely on high-speed strikes, the Greenland shark is a slow-moving scavenger and predator. To secure larger prey, such as seals, the shark employs a “grip and twist” mechanism.

When the shark bites into the prey, it rotates its entire body to create leverage and tear away chunks of flesh. This twisting motion, combined with the shark’s tooth structure, creates the spiral-shaped lacerations observed on the seal carcasses. The precision of the wounds is attributed to the way the shark’s teeth slice through the blubber layer as the animal rotates.

This discovery provides new insight into the foraging habits of the Greenland shark, suggesting that it plays a more active role in predating on marine mammals in the North Atlantic than previously understood. The identification of the “Corkscrew Killer” highlights how eDNA technology can solve long-standing ecological mysteries where direct observation of the predator is nearly impossible.

The Greenland shark is one of the longest-living vertebrates on Earth, with some individuals estimated to live for several centuries. Its slow metabolism and adaptation to near-freezing temperatures make it a dominant, albeit hidden, force in the deep-sea ecosystems of the North Atlantic.