Scientists have documented a striking new behaviour in orcas: working in pairs to ram giant sunfish at such high speed that the fish explode into thousands of fragments. The events, recorded in the Gulf of California off the coast of Mexico, have been described in a new paper published in the journal Frontiers in Ethology. Researchers have labelled the technique "ram-to-fragment" behaviour, and say it has never been formally described before.

In footage captured first in July 2024 and again in September 2025, the sequence follows a clear pattern. One adult orca holds a dead sunfish in its jaws, positioning it in the water, before releasing it just as a second orca accelerates upward from the depths and strikes the carcass at full speed. The impact is audible — described by witnesses as an overwhelming acoustic thud — and leaves behind a cloud of tissue fragments. Younger members of the pod then move in to feed on the scattered pieces, while the adults consume the main remains. Dr Kathryn Ayres, of the non-profit organisation Beneath the Waves, captured the first event on a GoPro camera and can be heard reacting in shock on the audio. "When you see a multi-ton apex predator charge a massive fish at that speed right next to your boat, the sheer acoustic thud and the resulting explosion of tissue are overwhelming," said co-author Erick Higuera, a marine biologist at Mexican non-profit Conexiones Terramar.

Scientists have proposed two main explanations, which are not mutually exclusive. The first is practical: sunfish, among the world's largest fish — growing to over three metres and weighing up to 2,000 kilograms — have tough, rubbery flesh. Breaking them into smaller pieces may help juveniles, whose jaws are not yet large enough to handle the intact carcass, feed more easily. The second explanation is play. Orcas, technically the largest members of the dolphin family, have a well-documented history of inventive social behaviour with no obvious survival benefit. In the 1980s, a pod began balancing dead salmon on their heads like hats — a trend recently revived. A subpopulation near Spain and Portugal has become known for unusual interactions with boats. "They throw kelp at each other, surf in boat wakes and engage in intricate tactical games," said Higuera. "Play is a core pillar of orca society."

Whatever the purpose, researchers say the coordination required — one animal stabilising the target while another executes a high-speed strike — points to a sophisticated level of cognitive planning. The behaviour also illustrates broader variation across orca populations worldwide, which are divided into distinct groups, or ecotypes, each with different diets, dialects, and hunting strategies adapted to their local environments.

The discoveries were made possible in part by wildlife tourism operators equipped with underwater drones and cameras, highlighting an increasingly valuable, if complicated, relationship between science and ecotourism. While citizen scientists have helped document previously unseen behaviours in whales and dolphins, concerns remain about disturbance to wildlife. Mexico introduced new regulations on swimming with orcas last year. Researchers emphasise that careful, respectful observation is key to ensuring such collaboration continues to shed light on the hidden complexity of ocean life.