(CNN) – It was a duel between orcas and dolphins, and the dolphin didn’t stand a chance.
In 2023, in coastal waters off Chile, a huge female orca pounced on a much smaller dolphin, causing it to jump into the air. In a few minutes, the unequal battle ended and the orca began to feed. But she didn’t eat dinner alone. As he grabbed the dolphin’s body, other orcas swam over to share bites of the food.
Meanwhile, researchers on a nearby boat recorded the feast on video and identified the prey as a dusky dolphin (Lagenoryhnchus obscurus), a small coastal species native to South America.
Scientists had previously documented killer whales (Orcinus orca) in the region pursuing both dusky dolphins and long-beaked common dolphins (Delphinus capensis). However, this new observation is the first evidence that dusky dolphins are hunted, captured and shared by killer whales in the Humboldt Current system, which flows north into the Pacific Ocean along the western coast of South America. .
Orcas are found throughout the world, and although there is only one species, there are multiple ecotypes, or groups that share similarities in their appearance and behaviors, including hunting strategies and prey preference. There are five ecotypes in the northern hemisphere and five in the southern hemisphere. The Humboldt Current killer whales have not yet been assigned to an ecotype, and documentation of their dolphin hunting provides clues as to which group this population might belong to, 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 groups of killer whales, such as those that live near Antarctica and off the western coast of North America. They are also not as famous on the internet as the orcas that have rammed ships in the Strait of Gibraltar and near Scotland. But marine biologists are working to fill that gap. After conducting studies and analyzing more than 10 years of data, photos and videos, scientists recorded 28 sightings of orcas in two locations in the Humboldt Current. Image by image, researchers are piecing together a clearer idea of the distribution and habits of these elusive whales.
According to Sarah Teman, a doctoral student at the School of Aquatic and Fishery Sciences at the University of Washington in Seattle, orcas are very social animals and there is still much to learn about their behaviors and how they can vary from one group to another. “Orcas around the world can have different diets, different communication styles and even different cultures,” said Teman, who was not involved in the research but has studied interactions between orcas and porpoises.
“We are still learning how diverse orca populations are,” he added.
In the Humboldt Current, cold, nutrient-rich water rises from the deep ocean. It transports nutrients that feed schools of anchovies and krill, which in turn are eaten by larger marine mammals, such as dolphins and seals, prey of orcas.
The lead author of the study, Ana María García Cegarra, associate professor at the Alexander von Humboldt Institute of Natural Sciences at the University of Antofagasta, Chile, and director of the Chilean Marine Megafauna Research Laboratory (CETALAB), dedicated the last decade to investigate the orcas of the Humboldt Current. For the study, she and her colleagues analyzed reports and media recorded between 2011 and 2023 by local fishermen and people on whale-watching tour boats in the Humboldt Penguin National Reserve and around the Peninsula. Mussels in northern Chile.
Scientists also conducted boat surveys in Mejillones Bay and filmed orcas with an aerial drone. Based on the associations between orcas, the researchers determined that there were at least two distinct social groupings, each with five to six individuals. Known as pods, these small orca communities typically consist of a matriarch and her descendants.
Dusky dolphins are about 2 meters long and weigh up to 85 kilograms. In comparison, an orca is up to 10 meters long and can weigh up to 11 tons (10 metric tons). In May 2023, scientists report in the study, there were two sightings of killer whales hunting dusky dolphins. In one case, a female orca chased a dolphin and threw it into the air; He then grabbed the dead dolphin in his mouth while other orcas swam around and fed on it. In the second incident, a female orca held a dead dusky dolphin while her calf and other orcas devoured the carcass in about 15 minutes.
Previous studies documented dolphin predation by killer whales in waters near California, Argentina and New Zealand. And in the Salish Sea, an inlet of the Pacific Ocean located between Washington state and British Columbia, Canada, a group of orcas that feed primarily on salmon repeatedly harassed and killed porpoises – but these orcas did not They eat the porpoises they kill.
According to the study, Humboldt Current killer whales did not feed exclusively on dolphins, but rather hunted leatherback turtles, South American fur seals and Humboldt penguins. The scientists also discovered signs of killer whale dental rake marks on the dorsal fin of a fin whale (Balaenoptera physalus). Although killer whales were not observed hunting fin whales, they are known to hunt and eat northern whales (Balaenoptera borealis) in waters near Chilean Patagonia. “Snow whales and fin whales are very similar,” so Humboldt Current killer whales probably also hunt fin whales, García Cegarra said in an email.
In the Southern Hemisphere, orcas of the type A ecotype are known to prey on dusky dolphins; Since Humboldt Current killer whales share this preference, they could be type A killer whales. But Humboldt Current killer whales have a smaller white eye spot than known type A killer whales. According to the scientists, genetic analysis of skin samples, which were not collected for this study, could help solve this problem.
According to García Cegarra, monitoring the Humboldt Current killer whales and knowing what they hunt and eat will help conservation groups protect the killer whales, which, according to the International Union for Conservation of Nature’s Red List, (a tracker of threatened and endangered species) and the Chilean Ministry of the Environment, are classified as “data deficient.” As a consequence, there are no management tools or strategies to protect them.
“Orcas play a vital role in the world’s oceans and are valuable in their own right,” Teman says. “The more we learn about whales, the better equipped we will be to protect the seas in which they live.”
The new research will also help scientists better understand the social interactions of orcas, such as how they teach their hunting strategies to their offspring. And there are other intriguing orca behaviors that are even less known.
For example, during one of the meals, a baby orca approached the scientists’ boat with a mouth full of dolphin meat, García Cegarra said in the email. A similar interaction between an orca and a diver had already been documented in Australia, but it had never been observed in the Humboldt Current. One interpretation is that the orca was offering to share its food, but scientists don’t know for sure, García Cegarra said.
However, the chances of documenting wild orca hunts this way are not great, he added. Orcas can swim long distances very quickly and usually travel in small groups, so encounters with orcas during research expeditions are usually rare.
“It’s quite a coincidence to be in the sea at the same place and time that the orcas decide to be hunting,” he said.
Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American, and How It Works magazine.
