In a dramatic encounter off the coast of Chile in 2023, a powerful female orca launched a much smaller dusky dolphin out of the water with a single, decisive blow. Within minutes, the battle was over, and the orca began to feast. But she was not alone in her meal; other orcas soon joined to share in the bounty. This rare event was captured on video by researchers aboard a nearby vessel, who identified the prey as a dusky dolphin (Lagenorhynchus obscurus), a species native to South America's coastal waters.

This observation marks the first recorded instance of dusky dolphins being hunted, caught, and shared by orcas within the Humboldt Current system, which flows northward along the western coast of South America. While orcas (Orcinus orca) are found worldwide and exhibit a range of ecotypes, or groups with shared characteristics, the orcas of the Humboldt Current have yet to be classified. This discovery could provide crucial insights into their classification, as reported in the journal Frontiers in Marine Science.

The orcas of the Humboldt Current are less studied than their counterparts in Antarctica or the western coast of North America, and their hunting behaviors are not as well understood. However, marine biologists are working diligently to bridge this knowledge gap. After a decade of surveys and data analysis, scientists have documented 28 sightings of orcas in two key locations within the Humboldt Current.

Understanding the Social and Hunting Behaviors of Orcas

Killer whales are highly social creatures, and their behaviors can vary significantly between groups. Sarah Teman, a doctoral student at the University of Washington in Seattle, notes that orcas worldwide exhibit diverse diets, communication styles, and even distinct cultures. The study of these elusive whales is ongoing, with researchers analyzing data, photos, and videos to build a clearer picture of their distribution and habits.

The Humboldt Current is rich in nutrients, supporting a thriving ecosystem that includes anchovies, krill, dolphins, seals, and orcas. Ana Maria García Cegarra, lead author of the study and director of Chile's Marine Megafauna Research Lab (CETALAB), has dedicated the past decade to studying these orcas. Her team's research has revealed at least two distinct social groupings, or pods, each consisting of a matriarch and her descendants.

Dusky Dolphins and Other Prey

Dusky dolphins, measuring about 7 feet (2 meters) in length and weighing up to 187 pounds (85 kilograms), are dwarfed by the massive orcas, which can reach lengths of 32 feet (10 meters) and weigh as much as 11 tons (10 metric tons). The 2023 study reported two sightings of orcas hunting dusky dolphins, with one female orca seen tossing her prey into the air before feeding alongside other orcas.

While orcas are known to prey on dolphins in other regions, such as California, Argentina, and New Zealand, the Humboldt Current orcas also hunt a variety of other marine life, including leatherback sea turtles, South American fur seals, and Humboldt penguins. The researchers even found evidence of orca tooth marks on a fin whale's dorsal fin, suggesting that these orcas may also hunt larger whale species.

Conservation and Future Research

Understanding the hunting habits of the Humboldt Current orcas is crucial for conservation efforts. Currently listed as "data deficient" by the International Union for the Conservation of Nature's Red List, these orcas lack specific management strategies for protection. Further research will not only aid in their conservation but also enhance our understanding of orca social interactions and hunting strategies.

Intriguingly, during one of the documented meals, an orca calf approached the researchers' boat with a mouthful of dolphin meat, a behavior previously observed in Australia but never before in the Humboldt Current. This could suggest a unique form of social interaction or even an offer to share food, although more research is needed to confirm this hypothesis.

Documenting orca hunts in the wild is a rare occurrence, as these creatures can cover vast distances quickly and often travel in small groups. "It's a great coincidence to be in the sea at the same place and time when orcas decide to hunt."  As our knowledge of these magnificent creatures grows, so too does our ability to protect the oceans they inhabit.