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Facts About Orcas

Orcas are the most widely distributed of all whales and dolphins, found in every ocean. But though the species is widespread, orca populations are actually very localized. The orca communities that live in the Pacific Northwest stay in that area, and those in the Antarctic stay south of the Equator. While they are very distant cousins, these populations have not interacted in thousands of years, resulting in significant differences.
Orcas leaping

Differences include their appearance, behavior, acoustics, and what they eat. These variations, plus genetic distinctions, support the existence of multiple kinds of orcas – what scientists call “ecotypes.” There are ten known ecotypes of orcas, but more may exist.

What is an orca?

An orca is a marine mammal. Did you know that orcas are actually dolphins? In fact, they are the largest member of the dolphin familyDolphins and whales are closely related – both are in the order Cetacea, which includes whales, dolphins, and porpoises.  Orcas were given the name “killer whale” by ancient sailors’ observations of groups of orcas hunting and preying on larger whale species.  They called orcas asesina ballenas, or “whale killer” – a term that was eventually flipped around to the easier “killer whale.”  Their Latin name, Orcinus orca, also reflects this observation of orcas feeding on large whales.  Orcinus translates to “of the kingdom of the dead,” and orca refers to a kind of whale.

What we now know is that not all orcas prey on other cetaceans.  Some populations specialize on fish, some on seals, some on sharks and rays, and some are generalists and eat many different things!  We also know that they are complex, highly social, and have different cultures – orcas have their own civilization under the sea.  Top predators, yes, but not the vicious “whale killers” that the ancient mariners thought them to be.  If you could give orcas another name, what would you call them?

What do orcas eat?

Looking at all populations, orcas are generalist eaters, consuming fish, seals and sea lions, dolphins and porpoises, sharks and rays, large whales, cephalopods (octopods and squids), seabirds and more.  However, different ecotypes specialize on specific prey, and it turns out orcas are picky eaters – once they’ve learned what their family eats, they aren’t likely to switch diets.

Culture is also a defining aspect of an orca’s ecotype.  In broad terms, culture refers to the inherited beliefs, values, and knowledge of a group with shared traditions, transmitted and reinforced by members of the group.  In orca populations, knowledge is passed down to younger individuals from their elders – what to eat and were to find it, how to catch it, who to avoid, vocalizations and calls unique to pods and family groups, and the distinct “accent” of the population.  In high productivity areas like Antarctic and the Pacific Northwest, multiple ecotypes co-exist in one large “community” of orcas, but despite the overlap in range, the ecotypes rarely interact and have even been seen to actively avoid each other.  Having multiple prey items to choose from probably led to the niche specializations we see today – millions of year ago, different groups started eating different things to avoid competing for the same food, and that eventually led to the development of ecotypes.  Now these groups are genetically different, in addition to their unique appearance and cultures.

What threats do orcas face?

Orcas worldwide face a number of threats, many of which are the same regardless of ecotype or region.  Prey depletion is a problem for many orca populations, as is biocontamination, increasing ship traffic, harassment, conflict with fisheries, habitat loss, risk of oil spills, and noise pollution.  In some regions – Greenland, Japan, Indonesia, and some Caribbean islands – they are still victims of whaling efforts.  Historically, populations in the Pacific Northwest and North Atlantic were targeted for live captures to be sold to oceanariums like SeaWorld.  The Southern Residents were extensively targeted and still struggle to recover – they have never come close to regaining their pre-capture population numbers.  Orcas in the Pacific waters off Russia are still captured and sold into captivity, including four taken in 2014.

In the Pacific Northwest, the three biggest threats are prey depletion, biocontamination, and increasing vessel traffic.  Resident orcas specialize on salmon; Chinook, or King salmon, makes up about 90% of their diet in the summer.  In the winter and spring, Resident groups move out of the sheltered inland waters of the Salish Sea into rougher coastal ocean waters, where it is harder to study them and figure out where they go and what they’re eating.  But we do know that they continue to eat Chinook and follow salmon runs on rivers along the west coast – from the Fraser and Columbia in the north to the Klamath and Sacramento in the south.  Unfortunately, Chinook stocks have crashed in the last century and are now mere fractions of their historical abundance.  Overfishing, habitat loss, dams blocking rivers and spawning grounds, and impacts from hatcheries and fish farms continue to contribute to declining salmon stocks, impacting Resident populations as well.  Legacy pollutants like DDT and PCBs continue to pollute oceans and contaminate orcas in many regions, even in the US, where they have been banned for decades.  Toxins accumulate in the prey of orcas and are transferred to individuals, where the pollutants are stored in blubber and fat reserves.  Increasing vessel traffic and ocean noise blocks the ability of orcas to communicate, forage, and echolocate.  For mammal-hunting orcas that rely on stealth to catch their prey, not being able to hear means they have trouble locating their next meal; fish-eating orcas rely on communication and echolocation to coordinate their foraging, and studies have shown that they increase the amplitude and volume of their calls to try and make themselves heard over increasingly loud background noise.

WDC works to protect orcas, and their homes, across the globe.  From ending captivity to dam removal efforts in the Pacific Northwest, WDC will not stop until all orcas, whales, and dolphins are safe and free.

Support provided by a grant from the Mountaineers Foundation