Scientists Capture Footage of Orcas Attacking Smaller Dolphins, Subduing Their Prey, and Sharing a Meal with Kin.
A new study published in the journal Frontiers in Marine Science on September 26 reveals the behavior of a mysterious group of orcas that science has yet to fully understand.
During a hunt, the orca (right) flips the dark-colored dolphin (left) out of the water. (Photo: Maikol Barrera).
In 2023, in coastal waters near Chile, a large female orca attacked a smaller dolphin, flipping it out of the water. Within minutes, this uneven battle concluded, and the hunter began to deal with its prey. However, it did not eat alone. While it held the dolphin tight, other orcas swam over to join in the feast.
The research team on a nearby boat recorded the meal and identified the prey as dark-colored dolphin (Lagenorhynchus obscurus), a small dolphin species native to South America that inhabits coastal areas. This is the first evidence that orcas from the Humboldt Current system—an ocean current in the Pacific that flows north along the western coast of South America—hunt and scavenge dark-colored dolphins.
Orcas (Orcinus orca) are found worldwide. They are divided into several “ecotypes”—groups with similarities in appearance and behavior, including hunting strategies and preferred prey. There are five ecotypes in the Northern Hemisphere and five in the Southern Hemisphere. However, the orcas of the Humboldt Current have not yet been classified into any ecotype.
Scientists know very little about the behavior of Humboldt Current orcas. In the Humboldt Current, cold, nutrient-rich waters rise from the deep ocean, nourishing small fish and other organisms such as krill. These, in turn, are preyed upon by larger marine mammals like dolphins and seals. Dolphins and seals then become prey for orcas.
A pod of orcas sharing a meal of dark-colored dolphin. (Photo: Luis Aguilar/CETALAB).
In the new study, lead author Ana Maria García Cegarra, an associate professor at the Alexander von Humboldt Institute of Natural Sciences at the University of Antofagasta, Chile, focused on studying Humboldt Current orcas. She and her colleagues examined detailed reports recorded from 2011 to 2023 in the Humboldt Penguin National Reserve and around the Mejillones Peninsula. They also conducted boat surveys in Mejillones Bay and captured footage of orcas using a drone.
The dark-colored dolphin measures about 2 meters in length and weighs 85 kg. In contrast, orcas can reach lengths of up to 10 meters and weigh as much as 10 tons. According to the new research, Humboldt Current orcas not only eat dolphins but also feed on leatherback turtles, South American fur seals, and Humboldt penguins.
Monitoring Humboldt Current orcas to understand their hunting and feeding habits will be beneficial for conservation organizations. This group of orcas is described as “data deficient” in the Red List of the International Union for Conservation of Nature (IUCN) and the Chilean Ministry of Environment, according to García Cegarra. Therefore, there are currently no clear management tools or strategies in place to protect them.
“Orcas play a crucial role in the world’s oceans and have inherent value. The more we learn about orcas, the better equipped we are to protect the waters they inhabit,” shared Sarah Teman, a researcher at the School of Aquatic and Fishery Sciences at the University of Washington.
