Killer whale tosses dolphin into the air

Scientists have filmed killer whales attacking smaller dolphins, taking down their prey and sharing meals with their mates.

New research published in the journal Frontiers in Marine Science on September 26 reveals the behavior of a mysterious group of killer whales that scientists do not fully understand.

During a hunt, a killer whale (right) tosses a dusky dolphin (left) out of the water. (Photo: Maikol Barrera).

In 2023, off the coast of Chile, a large female killer whale attacked a smaller dolphin, tossing it out of the water. Within minutes, the unequal battle was over and the predator was ready to tackle its prey. But she wasn't eating alone. While she held the dolphin, other killer whales swam in to join her in the feast.

A team on a nearby boat filmed the meal and identified the prey as a dusky dolphin ( Lagenoryhnchus obscurus ) , a small porpoise native to South America that lives close to shore. This is the first evidence that killer whales in the Humboldt Current system — a Pacific ocean current that flows north along the west coast of South America — hunt and co-predate dusky dolphins.

Killer whales ( Orcinus orca ) are found worldwide. They are divided into several 'ecotypes' – groups that share similarities in appearance and behavior, including hunting strategies and preferred prey. There are five ecotypes in the Northern Hemisphere and five ecotypes in the Southern Hemisphere. However, the Humboldt Current killer whale has not yet been classified into an ecotype.

Scientists know very little about the habits of the Humboldt Current killer whale . In the Humboldt Current, cold, nutrient-rich water swirls up from the deep sea, feeding anchovies and crustaceans. These are then eaten by larger marine mammals such as dolphins and seals. Dolphins and seals, in turn, are preyed upon by killer whales.

Killer whales share a meal of a dark 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 in Chile, focused on killer whales in the Humboldt Current. She and her colleagues looked closely at records from 2011 to 2023 in the Humboldt Penguin National Reserve and around the Mejillones Peninsula. They also conducted ship surveys in Mejillones Bay and filmed killer whales with drones.

The dusky dolphin is about 2m long and weighs 85kg. Meanwhile, the killer whale is up to 10m long and can weigh 10 tons. According to new research, the Humboldt Current killer whale eats not only dolphins but also leatherback turtles, South American fur seals and Humboldt penguins.

Monitoring the Humboldt Current killer whales and knowing what they hunt and eat would be very useful for conservation organizations. The group is listed as 'data deficient' on the Red List of the International Union for Conservation of Nature (IUCN) and the Chilean Ministry of Environment, according to García Cegarra. As a result, there are currently no clear management tools or strategies to protect them.

"Killer whales play a vital role in the world's oceans and they are valuable in their own right. The more we learn about killer whales, the better we can protect the waters they inhabit," said Sarah Teman, a graduate student at the University of Washington's School of Fisheries and Aquatic Sciences.