Orcas are the most widely distributed of all cetaceans (whales, dolphins and porpoises), found in every single ocean on the planet.
They are also one of the world’s smartest marine mammals, with large brains that allow them to store memories. This knowledge – what to eat, where to find it, how to catch it, who to avoid, which calls to use – is passed down to younger individuals from elders, resulting in a collective database shared within a community.
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Orcas have distinct ‘languages’ within their family groups, communicating using a range of clicks, whistles, pulsed calls, squeals, squeaks and screams.
Their highly tactical hunting techniques include intentionally beaching to capture prey on shore, creating waves to wash seals off ice floes and working together in groups to herd fish and attack larger prey such as whales.
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It was these sophisticated tactics that led orcas to be described as ‘killer whales’ by ancient sailors who observed pods of orcas hunting and preying on larger whale species.
Their Latin name, Orcinus orca, translates as ‘of the kingdom of the dead’ and orca refers to a kind of whale. Top predators they may be, but orcas are not the whales that history’s mariners declared them to be.
In fact, orcas are the largest of the dolphin family. A male orca can be up to 10m long, with a dorsal fin, unique to each animal, that can be up to 2m tall (the largest dorsal fin of all the cetaceans).
They swim fast and have been recorded at speeds of up to 54kmph. A wild orca pod can cover more than 160km in a day, foraging and socialising as they go.
They are generalist eaters, consuming fish, seals and sea lions, dolphins and porpoises, sharks and rays, large whales, cephalopods, seabirds and more. Some orca specialise in specific prey and it turns out they are picky eaters. Once they’ve learned what their family eats, they rarely switch diets.
If it’s herring that an orca family depends on as its primary food source, they might make a beeline for northern Norway during winter, when massive schools of the fish migrate into the fjords from summer feeding grounds further south.
What’s the largest killer whale gathering in the world?
From late October to mid-January, northern Norway, particularly the Troms region, sees one of the world's largest gathering of orcas, drawn by this annual herring migration.
The migration creates a predictable and concentrated area where orca can be seen hunting and feeding, often alongside humpback whales, with as many as 50-60 orca observed simultaneously.
The fjords offer deep, sheltered waters ideal for orca. The steep walls and narrow passages help them herd the fish, and the calm, clear waters enhance visibility. Thousands of orca travel to this spot each winter, making it one of the world’s most significant seasonal gatherings.
But scientists in Australia have discovered an even larger gathering, near Bremer Bay at the West Australian southern coastline.
From late austral spring to early autumn, around 100 orcas are seen feeding in the same confined region each year.
A 2021 study found that the Hood Canyon (where the orcas gather) produces a high flow of particulate organic matter (such as plankton) at great depth, which provides food for the deep-sea crabs, squids and other filter feeders that orcas feast on.
Top image: kayaker with a pod of orcas. Credit: Joel W. Rogers/Getty Images
