Dolphins on opposite Australian coasts independently invented same shell-fishing technique

Four thousand kilometres of ocean separate two populations of bottlenose dolphins that have arrived at nearly identical solutions to the same hunting problem. On Australia's west coast, researchers have long watched dolphins in Shark Bay use large empty seashells as fishing traps—a rare and deliberate tactic in which a dolphin positions a dead gastropod shell over a small fish hiding inside, lifts the heavy object to the surface, and lets the water drain away, bringing the prey within reach. Now, for the first time, scientists have documented the same behaviour occurring independently on the opposite side of the continent, in Queensland's Hervey Bay, suggesting that dolphins on both coasts reinvented this specialised foraging method without learning it from one another.

The behaviour itself is deceptively complex. A small fish fleeing a predator will dart into the opening of a dead shell on the seabed, seeking refuge. For most hunters, that would be the end of the chase. A shelling dolphin instead inserts its snout into the aperture, raises the entire shell—which can be quite large and cumbersome—and tips it above the waterline. As the water drains out, the trapped prey becomes accessible. The tactic requires more than simple object-carrying: a dolphin must locate a suitable dead shell, understand that a fish will hide inside it, keep the shell oriented correctly during the ascent, and manage the drainage without losing the meal. Marine scientists describe this as a tool-use behaviour and a specialised form of foraging.

Researchers led by Alexis Levengood have been conducting boat surveys in the Great Sandy Marine Park since 2022, and their recent paper in Marine Mammal Science presents the first published records of shelling from Queensland waters. The clearest evidence comes from two encounters in Hervey Bay during 2025. On 6 July, an adult female dolphin named Stevie Nicks was observed positioning a baler shell at the surface and lifting it clear of the water across three separate surfacings. Rain cut the observation short after nine minutes, and the researchers could not confirm whether she caught a fish. On 1 October, a mother dolphin named Maserati surfaced repeatedly with another baler shell while a drone recorded from above. The video captured a fish escaping from the shell, followed by Maserati dropping it and pursuing the prey. Three minutes later, Maserati's calf, Bentley, surfaced with the same shell in the same location. The calf inserted its snout into the opening, raised the shell, and slapped it against the surface. A photograph appears to show the body or tail of a suspected lizardfish protruding from the aperture. Again, the researchers could not definitively confirm a successful catch.

The geographic and social separation between Shark Bay and Hervey Bay makes the case for independent invention compelling. There is no plausible chain of ordinary dolphin associations connecting the two study sites across nearly four thousand kilometres of ocean. The authors argue that similar ecological conditions on both coasts—large empty shells on the seabed, small fish that shelter inside them, and dolphins with the cognitive and physical capacity to manipulate awkward objects—may have created similar opportunities for discovery. However, the researchers are careful with their language. They documented matching behaviour in distant populations, but they did not run experiments that could pinpoint the exact moment of invention on either coast. The conclusion is persuasive but inferential.

What makes shelling culturally significant is not merely that it was invented, but that it spreads. A 2020 study of Shark Bay's shelling dolphins analysed thousands of group encounters recorded over more than a decade and found that the behaviour travels between social associates. Using network-based diffusion analysis, researchers estimated that dolphins were ten to more than three hundred times more likely to acquire shelling through their social network than through genetic inheritance or learning alone. This was the first quantitative evidence of a toothed-whale foraging tactic spreading outside the mother-calf bond, suggesting that shelling moves horizontally between peers or obliquely from older non-parents to younger animals. The analysis also left room for separate discovery: the best model estimated that roughly forty-three per cent of dolphins may have acquired shelling outside the measured social network.

The Hervey Bay mother-calf sequence offers a possible glimpse of how transmission might work. Bentley picked up the same shell three minutes after watching Maserati use it, placed its snout in the same opening, and attempted similar movements. The researchers call this potential evidence of vertical social learning—information passed from parent to offspring. Yet they stop short of claiming it as proof of deliberate teaching, which would require evidence that a knowledgeable animal changes its behaviour in the presence of a learner, incurs some cost, and helps the learner acquire a skill faster. The calf may have learned by observation, been drawn to an object its mother had just handled, or already possessed experience with shells. The researchers could not confirm a successful catch. Their conclusion is cautious: the event is consistent with maternal social transmission and deserves further observation.

The Queensland evidence remains modest—two detailed encounters in 2025, three dolphins, and two earlier photographs from 2013 and 2019 that lack precise detail but suggest shelling was present years before the recent research. Shelling is so brief and rare that more practitioners may remain unseen. Longer observation, individual life histories, and social-network data will be needed to understand how often the behaviour occurs and how calves or peers acquire it. For now, the two coasts present a natural parallel: similar prey, similar shells, and similarly flexible minds appear to have produced one remarkably similar invention. Once discovered, the trick may cease to belong to one clever dolphin and begin moving through a population as culture—a tradition born from independent innovation and sustained by social learning.