Scientists Document Bizarre New Orca Behaviour in the Sea of Cortez

Scientists studying orcas in Mexico‘s Sea of Cortez have documented a behaviour that appears to be new to the scientific record — and they still aren’t sure exactly why the whales are doing it.

The behaviour involves one orca carrying a dead sunfish while another whale charges towards it at speed, striking the fish and sending pieces of tissue through the water.

Researchers have observed the behaviour on two separate occasions, more than a year apart, suggesting that this was not simply a one-off encounter.

In the first observation, a juvenile orca was present and began feeding on the smaller pieces of the sunfish after the impact. This has led researchers to suggest that the adult whales may have been deliberately breaking the fish into smaller, more manageable pieces for the younger member of the group.

But feeding may not be the whole story.

Scientists Search for an Explanation

Orcas are well known for their complex social behaviour and have been observed interacting with prey without immediately consuming it. The coordinated nature of the sunfish encounters means the behaviour could potentially have several explanations, including feeding, processing prey, social interaction, and learning or play.

For now, scientists simply don’t know.

One of the observations took place in the channel of Isla Cerralvo on September 7, 2025, when researchers witnessed three adult female orcas and a calf carrying out the same “hold-to-ram” behaviour with a sharp-tail sunfish.

The discovery adds to the growing body of evidence that there is still much to learn about the behaviour of orcas, even among populations that have been studied for years.

Source: Frontiers in Ethology

The paper was published on 23 July 2026 and is by Kathryn A. Ayres, Austin J. Gallagher, Christine V. Avena, Carlos M. Duarte and Jesús Erick Higuera Rivas.