Orcas seen smashing giant sunfish in possible hunting ‘game’

A group of orcas has been documented violently ramming enormous sunfish into pieces, offering researchers a rare glimpse into what could be a form of play, food preparation or training among the highly intelligent predators.

The behavior was described in a study published Thursday in the peer-reviewed journal Frontiers in Ethology. The research examined two encounters recorded in Mexico's Gulf of California.

During one incident, a female orca was seen gripping a dead sharp-tail sunfish by its tail as a male charged directly into the fish at high speed. The female released the fish just before the collision, which shattered part of its body and produced a crunch that could be heard underwater.

"It was chaotic," said Erick Higuera, a marine biologist at Conexiones Terramar who witnessed the encounter. After reviewing the footage, he concluded that the sunfish had been deliberately targeted.

The study, titled Fragmentation of Sharp-Tail Sunfish (Masturus lanceolatus) Caused by High-Impact Ramming Behavior in Orcas describes the maneuver as a potentially coordinated and cooperative feeding strategy.

Orcas are known for developing sophisticated hunting methods, including joint attacks on seals, sharks and other marine animals. Different populations often use specialized techniques that are passed down through generations.

The latest observations involve the sharp-tail sunfish, one of five known ocean sunfish species and the only one researchers have documented being fragmented by orca ramming.

Sunfish are the world's heaviest bony fish and can grow several meters long and weigh more than a ton. Despite their extraordinary size, they are slow-moving and have few ways to defend themselves against killer whales.

The sharp-tail sunfish also possesses a protruding tail-like structure called a clavus, which may give orcas a convenient place to grip the animal while another member of the pod prepares to strike.

After the sunfish was broken apart, a juvenile orca immediately began eating the smaller pieces. This raised the possibility that the adults were dividing the carcass into portions that would be easier for a younger whale to consume.

Researchers said the behavior could therefore represent a form of parental investment. However, they have not ruled out other explanations, including social interaction and play.

Such behavior may strengthen relationships within a pod while allowing younger whales to observe and practice the communication, timing and precision needed during real hunts.

Slow-moving sunfish could provide ideal training targets because they pose little danger to the whales.

"They present a low-risk opportunity for these sub-adults, so they can practice strike precision and reinforce social bonds," Higuera said.