Mysterious pod of orcas found near Chile reveals new hunting techniques

Off the coast of Chile, in waters populated by krill and anchovies from the Humboldt Current system, lives an elusive and little-known population of orcas. Through citizen science and years of diligent monitoring, a team of scientists led by Dr. Ana García Cegarra of the University of Antofagasta is uncovering their secrets, starting with dinner.

García Cegarra’s team, which had previously observed these orcas using fishing boats to help them catch sea lions, has now spotted them successfully hunting dusky dolphins for the first time and sharing food among pod members. This new evidence of their feeding habits could help experts understand the connections between orca populations in the Southern Hemisphere, aiding conservation efforts.

“Studying orcas in their natural environment is a real challenge because they are top marine predators, travel long distances and live offshore, which makes observation difficult,” said García Cegarra, lead author of the study. The Frontiers of Marine Science“But understanding their role in the marine environment is crucial for the conservation of this poorly known species of the Humboldt Current.”

You are what you eat

Killer whales are predators with an extremely varied diet, but not all killer whales eat the same things. Populations can be classified into different ecotypes based on their dietary preferences, acoustics, and genetics. Understanding what Humboldt Current killer whales eat is therefore an important step in understanding where they fit among the world’s other killer whales.

There are five different ecotypes in the Southern Hemisphere: some, like type A and type B1 killer whales, focus on marine mammals, while other types prefer fish. Understanding where the Humboldt Current animals are located could help us understand how these populations interact with each other more broadly and help conserve them for the future.

García Cegarra and his colleagues used a combination of their own surveys and scientific data collected from whale-watching trips and fishing boats to monitor the population and track their hunting choices. The observers recorded the presence of orcas, the composition and location of groups, and took photos and videos that the scientists were able to cross-reference with catalogs of known individuals.

By combining this data with their own systematic surveys and drone imagery, the scientists mapped orca presence in the region and tracked group behavior and prey choices.

This allowed researchers to gather evidence that the Menacho pod of orcas was capturing dusky dolphins, a species that no orca in this region has ever successfully hunted. Dramatic footage shows the matriarch, Dakota, tossing a dusky dolphin into the air.

These observations could indicate that these orcas could belong to the type A ecotype, which hunts mammals. Their prey and the small size of their groups would be consistent with this hypothesis, although their white eye spots are smaller than those typical of type A orcas. They have also never been observed in Patagonia with other type A orcas.

“We would like to be able to obtain skin samples to analyze their genetic data, because there is no genetic information on the orcas from this region of the Southeast Pacific,” García Cegarra said. “However, they are very elusive and intelligent, which makes it difficult to approach them by boat for biopsies.”

Sharing the spoils

Scientists’ observations of dusky dolphin hunting also revealed that members of the Menacho pod shared their food. Food sharing is observed in many orca populations, sometimes to help feed their kin, and sometimes because the pod hunts cooperatively and each gets a share.

In this case, García Cegarra and his colleagues suggest that the Menacho pod shared food with their relatives, much like type A killer whales that hunt sea lions by deliberately beaching them: female orcas have been seen sharing meat with pod members, allowing their relatives to eat first.

García Cegarra stressed that more information and systematic studies are needed to fully understand and protect this secretive population of orcas.

“The fact that we observed newborn calves is important because it indicates that they have young, but we don’t know their survival rate,” she said. “Thanks to citizen science, we can track the presence of orcas along thousands of kilometers of coastline in northern Chile, but most orca sightings are opportunistic.”