Though they may have a reputation as being cold-blooded killers of the ocean who are ready to chow down on anything that crosses their paths, orcas are in fact very picky eaters.
Like humans, they have different dietary preferences depending on their social groups and geographical location.
Now, a team of marine biologists working in the Humboldt Current off the coast of Chile has observed an elusive group of orcas that have developed a taste for dusky dolphins – a small, acrobatic species of dolphin. Orcas have never before been seen hunting these animals.
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The finding suggests this group of orcas belongs to a subset of animals that prefers to eat marine mammals rather than fish.
Interestingly, the orcas were seen sharing the spoils of the hunt between their group, specifically allowing their family members to eat first, including newborn calves.
The research team documented the behaviour using a combination of their own scientific surveys carried out using drone cameras, along with data collected by citizen scientists who filmed the orcas while out on whale-watching or fishing trips.
“Studying orcas in their natural environment is very challenging as they are marine top predators, travelling long distances and living offshore, which makes observation difficult,” said Dr Ana García Cegarra, a marine biologist based at the Universidad de Antofagasta, Chile and lead author of the study.
“The fact that we have observed newborn calves is important because it indicates that they are having offspring, but we don’t know their survival rate.
“Thanks to citizen science, we can follow the presence of killer whales along thousands of kilometres of the coast of northern Chile — but most orca sightings are opportunistic.”
The team now plan to study the group more closely in the hope of discovering exactly where they fit into the global orca family.
“We wish we could obtain skin biopsy samples to analyse their genetic data, as there is no genetic information for orcas in this region of the Southeast Pacific,” said García Cegarra.
“However, they are very elusive and intelligent, which makes it difficult to approach them in the boat for biopsies.”
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