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It was a contest between a killer whale and a dolphin, and the dolphin didn’t stand a chance.
In coastal waters off Chile in 2023, a massive female killer whale attacked a much smaller dolphin, knocking it out of the water. Within minutes, the unequal battle was over and the killer whale began feeding. But it wasn’t eating alone. While it held onto the dolphin’s body, other killer whales swam up to share bites of the meal.
Meanwhile, researchers on a nearby boat were videotaping the feast, identifying the prey as a dusky dolphin (Lagenoryhnchus obscurus), a small coastal species native to South America.
Scientists have previously documented killer whales (Orcinus orca) in the area preying on both dusky dolphins and long-beaked common dolphins (Delphinus capensis). However, this new observation is the first evidence of killer whales hunting, capturing and sharing dusky dolphins with killer whales in the Humboldt Current system, which flows northward into the Pacific Ocean along the western coast of South America.
Killer whales are found worldwide, and while there is only one species, there are several ecotypes, or groups, that share similarities in appearance and behavior, including hunting strategies and prey preferences. There are five ecotypes in the Northern Hemisphere and five in the Southern Hemisphere. The Humboldt Current killer whale species has yet to be identified, and documentation of its dolphin prey provides clues about where this population might belong, the researchers reported Thursday in the journal Frontiers in Marine Science.
In general, little is known about the habits of Humboldt Current killer whales; they are not as well-studied as other killer whale populations, such as those that live near Antarctica and off the west coast of North America. They are also not as famous on the Internet as the infamous killer whales that collide with boats in the Strait of Gibraltar and near Scotland. But marine biologists are working to fill this knowledge gap. After conducting surveys and analyzing more than 10 years of data, photos and videos, scientists have recorded 28 killer whale sightings at two sites in the Humboldt Current. Image by image, researchers are piecing together a clearer picture of the distribution and habits of the elusive whales.
Killer whales are highly social animals, and there is still much to learn about their behaviors and how habits may differ between groups, scientists say. Sarah Teeman“Killer whales around the world can have different diets, different communication styles, and even different cultures,” said Tiemann, who was not involved in the research but has studied interactions between killer whales and porpoises.
“We are still learning how diverse killer whale populations are,” she said.
In the Humboldt Current, cold, nutrient-rich water flows in from the deep ocean. This water carries nutrients that feed schools of anchovies and krill, which in turn are eaten by larger marine mammals such as dolphins and seals—prey for killer whales.
Lead author of the study Anna Maria Garcia SegarraAndrea Jordan, an assistant professor at the Alexander von Humboldt Institute of Natural Sciences at the University of Antofagasta in Chile and director of the Laboratory for Marine Megafauna Research in Chile, has spent the past decade investigating orcas in the Humboldt Current. In the study, she and her colleagues examined reports and media recorded from 2011 to 2023 by local fishermen and people on whale-watching tour boats in the Humboldt National Penguin Reserve and around the Mejillones Peninsula in northern Chile.
The scientists also conducted boat surveys in Mejillones Bay and photographed the killer whales with a drone. Based on the associations between the killer whales, the researchers determined that there were at least two distinct social groups, each with five to six individuals. Young killer whale communities, known as killer whale pods, typically consist of a mother and her offspring.
Dusky dolphins are about 7 feet (2 meters) long and weigh up to 187 pounds (85 kilograms). By comparison, a killer whale weighs about 100 kilograms. Dimensions They grow up to 32 feet (10 meters) long and can weigh up to 11 tons (10 metric tons). In May 2023, scientists reported in the study two sightings of a killer whale hunting dusky dolphins. In one incident, a female killer whale chased a dolphin and tossed it into the air; she then held the dead dolphin in her mouth while other killer whales swam by and fed. In the second incident, a female killer whale held a dead dusky dolphin while her calf and other killer whales made quick work of the carcass, swallowing it in about 15 minutes.
before studies Some studies have documented killer whales preying on dolphins in waters near California, Argentina, and New Zealand. In the Salish Sea, a gulf in the Pacific Ocean between Washington state and British Columbia in Canada, a group of killer whales that feed mostly on salmon has repeatedly hunted dolphins. Harassing and killing porpoises However, these killer whales do not eat the porpoises they bully to death.
The Humboldt Current killer whales weren’t just preying on dolphins; they were also hunting leatherback sea turtles, South American fur seals, and penguins in the Humboldt Current, according to the study. The scientists also found evidence of killer whale tooth marks on the dorsal fin of a fin whale (Balaenoptera physalus). While no killer whales have been observed hunting fin whales, killer whales are known to hunt and eat sei whales (Balaenoptera borealis) in waters near Patagonia, Chile. “Sei and fin whales are very similar,” Garcia-Segarra said in an email, so it’s possible that Humboldt Current killer whales are also hunting fin whales.
In the Southern Hemisphere, Type A killer whales are known to feed on dusky dolphins; because Humboldt Current killer whales share this preference, they may be Type A. But Humboldt Current killer whales have a smaller white patch than known Type A killer whales. Genetic analysis of skin samples, which were not collected for this study, may help resolve this issue, the scientists said.
Tracking killer whales in the Humboldt Current and learning what they hunt and eat will help conservation groups protect killer whales, which are described as “data-incomplete” by the International Union for Conservation of Nature’s Red List (a tool for tracking threatened species) and Chile’s Ministry of the Environment, García Segarra said. As a result, there are no management tools or strategies to protect them.
“Killer whales play a critically important role in the world’s oceans and are valuable in their own right,” said Tiemann. “The more we learn about whales, the better equipped we are to protect the seas they inhabit.”
Further research will also help scientists better understand killer whales’ social interactions, such as how they teach their young hunting strategies. There are other interesting killer whale behaviors that are still poorly understood.
For example, during one feeding, a killer whale calf approached the scientists’ boat with its mouth full of dolphin meat, Garcia-Segarra said in an email. A similar interaction between a killer whale and a diver has been documented before in Australia, but never in the Humboldt Current. One explanation is that the killer whale was offering to share its food, Garcia-Segarra said, but scientists don’t know for sure.
However, she added that the chances of documenting killer whale hunts in the wild in this way are not great. Killer whales can swim long distances very quickly and usually travel in small groups, so encounters with killer whales during research trips are usually rare.
“It’s a wonderful coincidence that I was at sea at the same place and time that the killer whales decided to hunt,” she said.
Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American, and How It Works.
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